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Hydrocotyle Weed Management Plan For the Middle and Upper Canning River

Prepared for Perth NRM October 2015

Revised Final: January 2016

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Executive summary Hydrocotyle ranunculoides (Hydrocotyle, Floating Pennywort) a native aquatic plant of South and Central Americas had been introduced to Australia through the aquarium trade in the early 1990s. The species found its way into the creeks that drain into the Canning River, WA, probably by inadvertent, aquarium waste dumping, and by 1993, had established dense infestations in many freshwater areas of the River, upstream of the Kent Street Weir.

A clonal species, with vegetative reproduction as its primary strategy for growth and colonisation, Hydrocotyle grew to dense infestations at most infested, freshwater locations, posing a major threat to ecological (environmental), social and economic values (i.e. recreational uses and other uses, such as irrigation and drainage) of the creek systems, Lagoons, Wetlands and the Canning River itself.

Following introduction as a new species to Australia, the absence of natural enemies in this new environment may have assisted its establishment over a relatively short period of time. However, as a freshwater species, Hydrocotyle has shown to be particularly sensitive to salinity; and its colonisation is strictly limited to creeks, lagoon and riverine habitat, which are fresh water. Major changes in hydrology and urban stormwater drainage, which have occurred in the region, over time, are probable factors in the spread and colonisation of the species.

Like most aquatic plants, Hydrocotyle responds readily to available nutrients and thrives in nutrient-enriched soft mud. Its luxuriant growth, extensive biomass production and entrenchment in lagoons and wetlands, such as the Wilson Wetlands, show that nutrient enrichment, resulting from urban runoff, are a contributory factor, assisting colonisation.

Information review

A significant amount of local research was undertaken between 1992 and 1996 to better understand the plant’s biology and ecology, as a basis for undertaking management efforts by multiple stakeholders, led by The Swan River Trust and the WA Department of Agriculture. Following reviews of influential factors affecting the spread of Hydrocotyle and available control options, management interventions were attempted at various infested locations with the mapping of infestation areas and integration of various control methods, including herbicides.

Control and eradication of existing infestations had been the goal of the initial management programs in the 1990s. The control methods were largely based on manual removal of small-to-medium sized infestations, in combination with herbicide treatments; and regular inspections.

In the mid-1990s, the herbicide of choice was the systemic and non-selective herbicide Glyphosate as its Round-up® formulation which contained the surfactant polyethoxylated tallow amine (POEA). Large-scale applications of these treatments were identified as potentially toxic to various amphibians, including frog species, due to the presence of this surfactant.

Public concern subsequently led to the registration of Bi-active® Glyphosate (Roundup Biactive®) in 1995-96, containing a substantially less toxic surfactant and was specifically designed for use in aquatic habitat. In WA and other Australian States, Round-up Bi-active® became a recommended option for use in waterways for control of problematic weeds.

Differences in opinion regarding ‘what works’ and ‘what does not’ have existed among stakeholder groups; and concerns about the potential overuse of herbicides have also been expressed by some community groups and agency stakeholders.

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The success and effectiveness of the overall management, undertaken with some degree of co-ordination across jurisdictions and stakeholders, has been variable and intermittent, due to insufficient funding and variable resources available to stakeholders for Hydrocotyle management within their jurisdictions. A low level of priority attached to Hydrocotyle management and inadequate co-ordination of the management effort may have also contributed to the risk of re-infestation of susceptible areas.

Hydrocotyle Working Group: The formation of a Hydrocotyle ‘Working Group’ in 1998, represented by various stakeholders and community groups, has had a significant positive impact in facilitating the management effort, including raising public awareness. Despite concerted efforts by the Group to coordinate action and eradicate the weed since the late-1990s, Hydrocotyle has continued to infest waterways within the Canning River region.

Recognising the continuing risk of re-infestation across a larger area and spread into new areas, stakeholders have sought and received additional funding to develop a Hydrocotyle Weed Management Plan (Hydrocotyle WMP) following best practice Australian approaches and updated information on control from both WA and overseas.

Growth, Reproduction, Habitat and Environmental requirements

Knowledge of biology, ecology, habitat requirements and influential factors is important in planning the management of any problematic species. Hydrocotyle is an obligate freshwater species, without any particular preferences in terms of water velocity, water depth, bank slope, pH, dissolved oxygen or nutrients, thereby making it a generalist in its ecological response, within the limits of cool, freshwater bodies. Two distinct habitats favoured by Hydrocotyle have been identified where it can grow luxuriantly: these are high altitude tropical lakes of East Africa and South America (cooler climates); and low altitude coastal regions of the temperate zone of USA, South America, Australia and Europe.

Optimum photosynthesis occurs at temperatures between 25 and 35°C, and in high sunlight. Growth is fast in summer and in strong sunlight. Growth and regeneration rates of about 23 cm per day have been recorded overseas with biomass doubling every 3-7 days. The vegetative plant can remain relatively dormant over winter to avoid frost and low temperatures, and re-commence fast growth as temperatures rise and day length increases.

Hydrocotyle has relatively wide ecological amplitudes, tolerating a wide range of factors in aquatic environments - such as shade and nutrients - to varying degrees. It does not grow in water, and needs a substrate for rooting. Once established and rooted, it can produce mats or rafts that spread over water surfaces or moist riparian areas, building upon each layer. It is found rooted at the margins of lakes, ponds, ditches and slow-flowing canals and drainage ditches. The plant produces emergent leaves to 30 cm from the water surface; roots develop from every node of the stoloniferous growth form and the species can grow luxuriantly in eutrophic conditions. The species utilises both sexual reproduction by seeds and asexual reproduction by vegetative growth and fragmentation. Flowering and fruiting occurs in spring and summer and there is limited seed dormancy around 15 ºC (temperate species).

Vehicles of Spread: A range of vehicles cause Hydrocotyle to spread across catchments, waterways and continents by both seeds and other propagules (fragments). The species is introduced to new areas deliberately via the aquarium trade and can be spread through waterways via aquarium waste dumping and fragments carried downstream by flowing water. Spread can also occur via contaminated equipment.

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Current Infestation Levels

Recent surveys and mapping results indicate that the remaining colonies along the Canning River main channel (between the Kent Street Weir and Nicholson Road Bridge) and most of its shoreline areas are minor. Any remaining patches in the Mill Street Drain and Bannister Creek are also minor and quite small.

On the northern side of the River, major infestations still exist in the Wilson Wetlands and Lagoon complex, mostly located in the freshwater sections - Wilson 1 and 2. Hydrocotyle infestations vary in size, mostly in the range of about 25-50 m2; they are interspersed among Typha stands, or entrenched underneath Melaleuca trees. No Hydrocotyle exists in the saline, lower parts of the Wilson lagoon complex (i.e. Wilson 3).

Three lagoons on the southern side of the main river channel, alongside Marmot Way and their shorelines, have patchy, moderately-sized infestations. Those within the lagoons are floating mats, variable in size (mostly, 1-3 m2), located underneath the tree canopies.

Recent success in management

The review of recent results of the management program indicates that a very high degree of control and almost eradication of infestations has been achieved along the Canning River main channel and most shoreline areas either side of the channel, and in the Mill Street Drain and Bannister Creek. The high degree of success achieved has been due to regular (monthly) inspections, regular mapping and targeting of infestations, frequent manual removal where possible, and well-directed ‘spot’ treatments of herbicides.

In recent management efforts, the herbicide of choice has been the selective herbicide - Metsulfuron-methyl, to which Hydrocotyle is quite sensitive. The use of Metsulfuron has been preferred over Round-up Biactive®, because it affords a high degree of selectivity on native shoreline vegetation (mostly sedges and grasses).

Although Metsulfuron is not registered for aquatic use in Australia, its use for ‘spot treatments’ against Hydrocotyle (a declared pest species, to be controlled within WA) is covered by an off-label permit (PER 13333) obtained by the WA Department of Agriculture and Food.

To reduce herbicide use in waterways, preference has been to use the minimal effective dose (a quarter of the standard rate of Metsulfuron: 2.5 g active ingredient, per 100 L of water)1. In some instances, Metsulfuron has been mixed with Round-up Bi-active® (1 L/100 L), with which it is compatible. Spot treatments in the last few years have been either by motorised spray, or hand-held, knapsack spray. The use of a biodegradable vegetable oil surfactant (Endorse™, at 0.2% v/v) has made the treatments more effective, and in some upper riparian, terrestrial situations, the use of Pulse™ (an organo-silicone sticker) as an additive has also been effective.

Hydrocotyle Weed Management Plan

Despite various efforts to control and eradicate Hydrocotyle from the Canning River region, the historical infestations have survived for more than 20 years, and have expanded their invaded territory in associated Lagoons and Wetlands. As a result, stakeholders have sought additional funding and resources to contain the threat posed by Hydrocotyle to other areas, and to control and eventually eradicate existing infestations.

1 The standard Metsulfuron label rate for general weed control is 10 g/100 L of water of the commercial product (600 g active ingredient, a. i./kg).

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Given the complex ecological nature of the infested waterway systems, and the different opinions and objectives of users and managers of those waterway assets, the development of the Hydrocotyle Weed Management Plan (WMP) focussed on achieving a consensual approach to managing the weed in the affected areas.

The Hydrocotyle WMP was developed using the steps shown below. This included a review of historical research and management experiences, both in the Canning River region and overseas, and extensive stakeholder and community consultation, conducted through two facilitated workshops and one-on-one interviews.

Steps in developing the Hydrocotyle WMP Notwithstanding the differences of opinion on some issues, such as the potential impacts of herbicide use in waterways, the stakeholders agreed on the need to control and eventually eradicate Hydrocotyle from infested locations.

There was also consensus that – as in the past – Hydrocotyle management should be achieved using an integration of appropriate strategies and methods, with a preference for effective, non-chemical and environmentally-friendly methods.

Step 1 – Define the Goals and Objectives

Step 2 – Identify and Prioritise Weed/s

Step 3 – Map locations and extents of infestations

Step 4 – Research and review Biology, Ecology and Management of Weed

Step 5 – Set Priorities – What, Where and When?

Step 6 – Determine the best approach

Step 7 – Decide on Tools and Techniques appropriate for the Management Task

Step 8 – Develop Implementation Plan

Step 9 – Define how to Monitor and Report on Effectiveness

Step 10 – Define the process for future review

Strategic Approach

The strategic approach is one of adaptive management, which involves undertaking planned action against Hydrocotyle, learning from them and re-evaluating the effectiveness of management options, before re-implementing the control plans.

The strategic approach also recognizes that in Australia, best management of problematic species is all about tackling weed problems, not simply at the individual, local infestation level, but also at other scales, such as the management unit (e.g. conservation reserve, wetland, native vegetation remnant), catchment, landscape, waterway and the region as a whole.

This approach includes taking ‘direct action’, as well as ‘indirect action’ against contributory factors, integrating the following: (1) prevention, (2) eradication, (3) containment and (4) asset protection control activities – at times and places that make them most effective and efficient.

The Hydrocotyle WMP encompasses the following strategic weed management considerations:

Prevention of Hydrocotyle infestations to new areas through the vehicles of spread – either from new introductions; or from breakaway propagules;

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Integrated weed control options2 – physical methods (i.e. manual and mechanical control), non-chemical methods (i.e. use of heat – steam and/or flame; manipulation of water flows, water levels, lake drawdown, and/or salinity management); cultural methods (i.e. re-vegetation; shading; weed matting; competitive planting) and chemical control.

The known ecology and biology of Hydrocotyle, including seed production, soil seed-bank, seed longevity, requirements for germination and establishment, vegetation reproduction (rhizomes and stolons); ease of fragmentation, and the plant’s growth attributes (biomass production and mat-forming nature);

The extent of the overall infestation and the densities of the populations and the economics and feasibility of control; and

The nature of the invaded environment, including that of non-target vegetation, as any control technique has potential side effects on the native flora and fauna.

Tactical Approach – Operational Management of Hydrocotyle

Information on the consequences of different weed management regimes upon biodiversity and environmental values of the Canning River and its associated waterways is generally inadequate. Despite this, the Hydrocotyle WMP makes an informed assumption (confirmed by stakeholders) that the positive benefits achievable for environmental, social and economic values in implementing the Hydrocotyle WMP are more desirable than the effects of the weed itself.

Stakeholder engagement

Stakeholder engagement is a crucial part of managing weeds in Australia. To achieve this, major stakeholders were engaged and consulted widely in developing the Hydrocotyle WMP. The following key visions were shared by all stakeholders:

Eradication of Hydrocotyle from the Canning River region; and

The continuation of positive and enduring stakeholder collaboration in managing Hydrocotyle in the Canning River regions.

Additional goals for the Hydrocotyle WMP, established by the stakeholders include: (a) Emphasise the application of non-herbicide control methods; (b) Empower the community to continue to deliver benefits for the Canning River environment; (c) Increase community awareness and education of aquatic weed problems; (d) Retain community enjoyment of the river environment; and (e) Ensure the Hydrocotyle WMP is a benchmark for aquatic weed management.

Site-specific Management and Implementation

Consideration of the nature and extent of existing Hydrocotyle infestations, as well as various site-specific considerations, were used in prioritising the infested areas for management action. Three important factors used for prioritisation were: (1) Potential for further spread within or beyond an infested area; (2) Consequences and the impact of on-going infestation; and (3) Management feasibility within a given management area.

2 The use of natural enemies as biological control has not yet been developed in Australia or overseas. However, future research on a bio-control agent may be warranted, given that it is a highly effective method against many aquatic weeds.

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Other important considerations were: knowledge of what combination of methods has worked and what has not; and which ‘Asset owners’ (agencies) have primary control responsibility.

The recommended management zones and priorities are as follows:

Management Zone 1 – Wilson Wetlands and areas within the Canning River Regional Park and adjacent land owned by Christian Brothers, managed by a collaborative arrangement and partnership between the Wilson Wetlands Action Group (WWAG), the Department of Parks and Wildlife (DPaW) and the City of Canning; (Priority: Medium);

Management Zone 2a – Canning River Main Channel from Kent Street Weir to Nicholson Bridge and the river bank areas in the Canning River Regional Park; managed by the Swan River Trust (now part of DPaW) (Priority: Highest);

Management Zone 2b - Three Wetland areas, which are integral parts of the southern side of the Canning River are proposed as a new Management Zone; Hydrocotyle infestation levels are considerably lower than in Wilson Wetlands; (Priority: Medium);

Management Zone 3 – Water Corporation Infrastructure – Welshpool Basin and Mill Street Drain (Priority: Highest);

Management Zone 4 – Bannister Creek; managed by City of Canning (Priority: Highest);

Management Zone 5 - Collier Pines Drain at Bodkin Park, Waterford. Managed by City of South Perth and Water Corporation (Priority -Highest - almost eradicated)

All areas where control action taken thus far has been successful receive the highest priority ranking, so that eradication of Hydrocotyle from these sites can be attempted. The time-frame for this is suggested to be the next 12-24 months.

The Wilson Wetlands (Zone 1) and the Lagoons on the southern side (Zone 2b) have some difficult-to-access infestations, which require different combinations of approaches, significantly more effort, time and resources for management, and careful consideration of safety for the staff involved. As a consequence, a Medium priority ranking is justified with a longer time-frame (3 to 5 years) for Hydrocotyle management within these wetlands.

The Management Plan envisages modifications depending on the actual results of tried control methods which do not achieve expected results. However, it should be regarded as a tool to achieve better outcomes, over a given period of time.

Goals of the Hydrocotyle WMP are set as follows:

Goal 1: A collaborative framework is in place that enables stakeholders to work together in an integrated manner to manage Hydrocotyle infestations and new outbreaks in the Canning River and adjacent waterways and wetlands.

Goal 2: An overall reduction in the extent and intensity of infestations is achieved and eradication from some locations.

Goal 3: Further spread of the weed beyond current boundaries is effectively prevented.

Goal 4: All stakeholders are involved in cooperative effort against Hydrocotyle incursions; including the implementation of effective education and awareness programs.

Goal 5: New technologies and management options advised through research and development are supported and promoted in the management of Hydrocotyle in the region

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Specific actions, performance indicators and responsibilities for each Management Zone and the above Goals of the Hydrocotyle WMP are provided in the plan. It is recommended that the Hydrocotyle Working Group lead the implementation of the plan.

Monitoring and Review of Hydrocotyle WMP

Monitoring and reporting should be an integral part of implementing the Hydrocotyle WMP and should include:

(a) Annual reporting on implementation, particularly with regard to Federal funding;

(b) Report to be compiled by the relevant lead implementing agency and submitted to the Hydrocotyle Working Group and to all stakeholders, with reporting on achievement of each action;

(c) Annual survey of Hydrocotyle populations recorded on a central database and report of comparison with previous years made; and

(d) Review of the Hydrocotyle WMP in 2018 (after 3 years) and changes to be collaboratively developed through the Hydrocotyle Working Group and other stakeholder inputs.

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Table of Contents 1. Introduction..................................................................................................................................... 1

1.1 Background .......................................................................................................................... 1 1.2 Objectives of the Plan .......................................................................................................... 1

1.3 The Problem ........................................................................................................................ 2

2. Information Review ........................................................................................................................ 6

2.1 Hydrocotyle Growth attributes and reproductive strategy.................................................... 6

2.2 Management experiences - Overseas ................................................................................. 8 2.3 A Brief History of Hydrocotyle management in the Canning River and

associated waterways .......................................................................................................... 9

2.4 Recent Management Effort ................................................................................................ 11

2.5 Levels of Current infestations ............................................................................................ 15

3. Key Issues .................................................................................................................................... 18 3.1 An adaptive management approach .................................................................................. 18

3.2 Negative Impacts of Hydrocotyle ....................................................................................... 19

3.3 Beneficial Uses of Hydrocotyle .......................................................................................... 19

3.4 Stakeholder and Community Engagement ........................................................................ 19

3.5 Management Principles and Strategic approach ............................................................... 21 3.6 Other key Issues ................................................................................................................ 21

4. Hydrocotyle Management Options ............................................................................................... 27

4.1 Strategic Weed Management ............................................................................................ 27

4.2 Integrated Weed Management (IWM) ............................................................................... 27

4.3 Factors affecting choice of control methods ...................................................................... 28 4.4 Non-Chemical Control Methods ......................................................................................... 29

4.5 Chemical Control – Herbicides .......................................................................................... 37

4.6 Integrated Control .............................................................................................................. 39

5. Hydrocotyle Weed Management Plan ......................................................................................... 41

5.1 Justification for Management Plan ..................................................................................... 41 5.2 Overall Aim of WMP ........................................................................................................... 41

5.3 Objectives of the WMP ...................................................................................................... 42

5.4 Legislative Control and Prevention .................................................................................... 42

5.5 Stakeholders ...................................................................................................................... 43

5.6 Mapping of Infestations ...................................................................................................... 44

5.7 ‘Site-Specific Management and Management Zones ........................................................ 46 5.8 Specific Management actions ............................................................................................ 46

5.9 Considerations and Opportunities ..................................................................................... 56

5.10 Management Goals, Actions and Responsibilities ............................................................ 56

5.11 Implementation Schedule .................................................................................................. 60

5.12 Training .............................................................................................................................. 60

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5.13 Monitoring and evaluation .................................................................................................. 60

5.14 Performance indicators ...................................................................................................... 61

5.15 Benefits .............................................................................................................................. 61 5.16 Lead Implementer – ‘Hydrocotyle Working Group’ ............................................................ 61

5.17 Stakeholder Roles and responsibilities .............................................................................. 62

5.18 Re-evaluation of the Hydrocotyle Management Plan ........................................................ 63

6. References ................................................................................................................................... 64

List of Tables Table 1 Herbicide treatments at Mill Street Drain and Bodkin Park ............................................... 12

Table 2 Triple Bottom Line Impacts of Hydrocotyle*....................................................................... 20

Table 3 Scoring System for assessing spread and impact ............................................................. 24

Table 4 Herbicides recommended for controlling Hydrocotyle ranunculoides* .............................. 37

Table 5 Declared Plant Classes in WA and Actions required by Law ............................................ 42

Table 6 Management Units - Prioritisation for Control with rationale* ............................................ 47

Table 7 Specific Management Actions recommended for Management Units ............................... 51

Table 8 Management Goals, Action and Responsibilities for the Hydrocotyle WMP ..................... 57

Table 9 Summary of Stakeholder Roles and Responsibilities ........................................................ 62

Table 10 Key Issues and Strategies ................................................................................................. 69

Table 11 Summary of Discussions with Stakeholders ...................................................................... 70

Table 12 Summary of Discussions with Stakeholders at Workshops ............................................... 71

Table 13 Some monitoring data from Wilson Wetlands Water Quality Monitoring ........................... 84

List of Figures Figure 1 Canning River regions – Main River Channel, Wetlands and Lagoons .............................. 5

Figure 2 Life cycle of Hydrocotyle ranunculoides (Source: Hussner and Lösch 2007) ..................... 7

Figure 3 Known infestations of Hydrocotyle in 2007 (from mapping conducted by SERCUL) ........................................................................................................................... 16

Figure 4 Known infestations of Hydrocotyle mapped by SERCUL in May 2015 ............................. 17

Figure 5 Schematic diagram showing the adaptive management approach that underpins the Hydrocotyle Management Plan .................................................................................... 18

Figure 6 Extent of Hydrocotyle infestations in the Canning River Region, Lagoons, Wetlands and Tributaries (July 2015) ................................................................................ 45

Figure 7 A Map of Wilson Wetlands showing the main waterbodies (Wilson 1 –freshwater; Wilson 2 and Wilson 3 both saline), drainage channels and locations of WWAG’s Water Quality monitoring points ...................................................... 78

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Figure 8 An aerial image showing Hydrocotyle infestations on the lower section of Wilson 2 Wetlands ......................................................................................................................... 79

List of Plates Plate 1 Hydrocotyle- leaves with lobes, succulent stalks ................................................................. 2

Plate 2 Dense infestations growing on shallow water ...................................................................... 2

Plate 3 Hydrocotyle- umbel and flowers .......................................................................................... 4

Plate 4 Aquatic habit - growing on shallow water ............................................................................ 4

Plate 5 A view of dense Hydrocotyle infestations in Wilson Wetlands ............................................ 4

Plate 6 An infestation in a canal in UK –removed by mechanical equipment (Source: Newman, 2006) .................................................................................................................. 31

Plate 7 Amphibious crafts ‘Truxor’ used for mechanical removal of aquatic plants (Source: Australian Catchment Management Website, 2015) .......................................... 32

Plate 8 A close up view of Centella asiatica in upper riparian areas ............................................. 34

Plate 9 Extensive Centella stands in Canning River Regional Park .............................................. 34

Plate 10 Weevil – Listronotus elongatus feeding damage on Hydrocotyle ...................................... 36

Plate 11 Hydrocotyle growing out of Typha infestations (14/2/2012) at Wilson Wetland 2 ............. 81

Plate 12 Hydrocotyle infestations in Wilson Wetland 2 (14 Feb 2015) ............................................ 81

Plate 13 Hydrocotyle removal by hand by WWAG volunteers at Wilson Wetland 2 (16 April 2015) .......................................................................................................................... 82

Appendices Appendix A – Summary of the Outcomes of Consultation with Stakeholders

Appendix B – A Summary of Key Issues raised in Stakeholder Discussions

Appendix C - Overview of A Weed Management Plan

Appendix D – An Update on Hydrocotyle Management at Wilson Wetlands

Appendix E – Minimising Potential Impacts of Herbicide Use

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Acknowledgements The following people and organisations took part in the consultation process and in the Workshops, and assisted in developing the Hydrocotyle Weed Management Plan (WMP). Their assistance is gratefully acknowledged.

Name Agency / Group

Kelly Fulker; Greer Gilroy; Luke McMillan Perth NRM

Brett Kuhlmann and Matt Grimbly SERCUL

Debbie Besch - Healthy Rivers Coordinator Department of Parks & Wildlife (formerly Swan River Trust)

John Snowden - Riverpark Operations Officer Department of Parks & Wildlife (formerly Swan River Trust)

Jenni Andrews (Coordinator Conservation and Environment) and Matthew Box (Operations Officer)

City of Canning

Julie Ophel - Environmental Officer City of South Perth

Michael Cobby - Operations Officer Department of Parks & Wildlife (DPaW)

Russel Gorton, Chairman, WWAG Wilson Wetlands Action Group (WWAG)

Jo Stone and Richard Stone Canning River Regional Park Volunteers

Stuart Martin; Vid Talevski; Martin Gehrmann Martins Environmental Services

Nathan Pearce - Director and Operations Manager Bunyip Contracting

Andrew Reeves, Development Officer Department of Agriculture and Food, WA

Karen Warner Eastern Metropolitan Regional Council

The preparation of the Hydrocotyle Weed Management Plan was funded by the Australian Government’s National Landcare Programme.

Abbreviations SERCUL South East Regional Centre for Urban Landcare

DPaW Department of Parks & Wildlife (formerly Swan River Trust)

WWAG Wilson Wetlands Action Group

DAFWA Department of Agriculture & Food, WA

Hydrocotyle WMP Hydrocotyle Weed Management Plan

SCRR Swan Canning River Recovery Programme

POEA Polyethoxylated tallow amine

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1. Introduction 1.1 Background

In January 2015, the Federal Environment Minister Greg Hunt announced the Swan Canning River Recovery (SCRR) Programme, a $1 million commitment to improve the health of the Swan and Canning Rivers funded through the Australian Government’s National Landcare Programme. The programme aims to eradicate the Hydrocotyle weed, provide support for practical, community environmental action and help people understand how their actions affect the river.

Perth NRM, a peak natural resource management body, are managing the investment over two years, working in partnership with the local environmental community to deliver the outcomes required of this funding.

The Programme outcomes are:

- Local decision making relating to the development and implementation of the project through key stakeholders via a local steering group.

- Weed control and management in the Middle Canning estuary with a focus on controlling the weed, Hydrocotyle.

- Greater community action in the recovery of the Swan-Canning River system within the Middle Swan estuary and Middle Canning estuary.

- Improved community awareness of the behavioural changes needed to reduce nutrient loads entering the Swan-Canning River system in the Middle Swan estuary and Middle Canning estuary.

One component of the Programme was to undertake the development of a Hydrocotyle Weed Management Plan (hereafter, referred to as the Hydrocotyle WMP) for the middle and upper Canning River (Canning Bridge to Nicholson Bridge), in consultation with key stakeholders and the local steering group (Hydrocotyle Working Group).

The development of the Hydrocotyle WMP was to be guided by previous, evidence-based knowledge and local actions that have been taken over the past twenty five or so years, to contain, control and eradicate Hydrocotyle from the infested Canning River areas.

1.2 Objectives of the Plan

The primary objectives of the Hydrocotyle WMP are as follows:

Develop a strategic approach to managing Hydrocotyle in the middle and upper Canning River, based on community consultation and available evidence and history;

Develop an Implementation Plan, also in consultation with the local Landcare community, assigning priorities to undertaking weed management actions in infested areas;

Ensure the SCRR Priority Weed Management Program aligns with and complements the Hydrocotyle Management Plan and the SCRR Direct Community Action program.

Specific Objectives

Review the history of Hydrocotyle management studies and efforts in the area to identify gaps in knowledge, understand the factors that contributed to spread, and evaluate historical control methods;


Map the extent and distribution of Hydrocotyle within the management area, to inform the management zoning and prioritisation of actions;

Identify/assess a range of non-herbicide, site specific management options for successful long-term management of Hydrocotyle in the area;

Determine the environmental risks associated with each management option; identifying preferred locations, and specific actions;

Provide recommendations on all options and the most appropriate combination of management options and approaches;

Develop implementation strategies to achieve potential eradication of Hydrocotyle from infested locations and responsible agencies and stakeholders; and

Establish a framework for long-term management of Hydrocotyle.

1.3 The Problem

Hydrocotyle ranunculoides, called the ‘Floating Pennywort’ (or Hydrocotyle), is a native of North America, but has become naturalised in Central and South America. In its native range, Hydrocotyle occurs in, and at the margins of, slow-flowing, warm and nutrient-rich water in Argentina, Brazil and Paraguay, also in southern states of the USA (Hussner et al., 2012 and references therein). Outside its native range, it is widespread in the United Kingdom, the Netherlands, Belgium, and present in France, Ireland, Italy, Germany, Australia, Angola, Ethiopia, Kenya, Malawi, Tanzania, Uganda, Democratic Republic of Congo, Madagascar, Rwanda and Zimbabwe and possibly also in Sudan (Newman et al. 2009). Wherever it grows in introduced areas, it is considered to be a problematic invasive species,

In Europe, it is found in and around canals, lakes, rivers, streams, ditches, and garden ponds. Extensive infestations have been recorded in the Netherlands and in southern mainland Europe. According to Newman and Duenas (2010), Hydrocotyle was first brought to the United Kingdom in the 1980s by the aquatic nursery trade, for tropical aquaria and garden ponds, although the first note of concern over its potential to become a weed had been published in the UK, as far back as in 1936.

Hydrocotyle (Plate 1 and 2) was first observed in sections of the Canning River, mostly between the Nicholson Road Bridge and Kent Street Weir in 1983 and in the following years spread throughout the Canning River Regional Park (Webster, 1994), including adjoining creeks and in associated wetlands, such as Bannister Creek and Wilson Lagoon.

Plate 1 Hydrocotyle- leaves with lobes, succulent stalks

Plate 2 Dense infestations growing on shallow water


Records indicate that it was first observed in Bannister Creek, a tributary of the Canning River in 1983, and remained relatively static until 1991 when it suddenly spread (Swan River Trust, 1996). In February 1989, the infested area of river covered by Hydrocotyle, between the Kent Street Weir and Nicholson Road Bridge in the Canning River was estimated to be only 0.16% of the area, and the species was not considered a problem.

In 1991, Hydrocotyle suddenly expanded and by September 1992, its cover had increased to an alarming 29-30% of the open water area between the Kent Street Weir and Nicholson Road Bridge (Klemm et al., 1993). Infestations had extended throughout the drainage network into the river and adjacent wetlands, disrupting the ecology and recreational uses of the waterways, and posed a threat to other waterways (Ruiz-Avila and Klemm, 1996).

Hydrocotyle was recognised as an aquatic species that has the potential to develop into a serious environmental, economic and recreational threat to other lakes and waterways. The mass of plant material in the Canning River posed a potential risk of spread within the State, and also throughout Australia (Webster, 1994).

The distribution of Hydrocotyle is restricted to freshwater habitats, where the plant makes rapid growth during the warm months of the year and forms dense floating mats which can cover the waterway from bank to bank. If unmanaged, Hydrocotyle can restrict movement of recreational boating, alter ecosystems and spread to other lakes and waterways. Hydrocotyle stems are mostly creeping (i.e. rhizomatous stems and stolons) and produce profuse, hair-like adventitious roots from the nodes, which usually occur at intervals of approximately 4-6 cm (Newman and Dawson, 1998). The stems and leaf stalks are hairless and somewhat fleshy in nature with aerenchyma, which aid in floatation.

Hydrocotyle leaves are mostly emergent, rising on stalks from the horizontally-growing stems. The leaves are alternately arranged along the stems and are also hairless. The leaves (Plate 1) are typically 2.5-4 cm across, but can often be large (4–12 cm across) and can attain a maximum diameter of about 18 cm. They are almost round in shape with a deep split, or are occasionally kidney-shaped with shallow or deep lobes and bluntly toothed margins. Leaves and stems may stand out of water about 40 cm above the water surface in large infestations, while the interwoven mat of roots can sink down to a depth of about 50 cm (Newman and Dawson, 1998).

Hydrocotyle flowers are arranged in clusters (i.e. compound umbels), arising from the leaf axils and are often hidden underneath the leaves (Plate 3; Plate 4). These flower clusters consist of a stalk (peduncle) which has several 1-5 cm long branches, each bearing a smaller cluster (an umbel) of 5-10 flowers. The tiny flowers are white, greenish or yellowish in colour with five minute petals and no obvious sepals. Flowering occurs mostly during spring and summer.

The fruit (mericarp) is oval-elliptic to round in shape, green in colour, 1-3 mm long, flattened, and has faint ribs. It divides into two halves when mature. Mature seeds are light to dark brown in colour; about 3 mm long and there are two seeds set in each fruit/flower.

Whilst the reproduction by seeds is well established for Hydrocotyle, its primary growth strategy is vegetative reproduction via stolons and stem fragments. Seed reproduction adds to the persistence and capacity of the species to disperse and spread (Webster, 1994). The management implication is that even if the vegetative biomass is controlled and removed, seeds could remain viable in slushy mud. Therefore, timely management action is needed to reduce the sexually mature vegetative growth leading to the production of flowers, fruits and seeds.

Given favourable conditions, Hydrocotyle is capable of forming extensive mats from the smallest root or stem fragments. Longer distance dispersal of stem fragments usually occurs by water movement and floods or as a result of human activities (e.g. dumped aquarium waste).

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23creeping

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23stolons

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23nodes

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23alternately%20arranged

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23lobed

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23umbels

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23axils

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23peduncle

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23umbel

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23petals

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23sepals

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23elliptic

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23stolons


Plate 3 Hydrocotyle- umbel and

flowers Plate 4 Aquatic habit - growing on

shallow water

The current distribution of Hydrocotyle in the Canning River region has been mapped, based on the work of community groups and agencies involved in its management. A program of regular inspections by a number of agencies and community groups has provided accurate information on the current distribution, extent and abundance in the management area.

Hydrocotyle infestations in open water areas, in drains, and in slushy mud in wetlands and lagoons are currently managed in the Canning River region using a number of methods. These include manual removal of small populations in soft mud and the use of herbicides - Glyphosate and Metsulfuron-methyl. Whilst these methods have had varying success, this WMP takes into consideration all options, including environmentally-sound, non-herbicide options, as well as site specific approaches and techniques that may be applicable to specific, environmentally-sensitive sites, such as the Wilson Wetlands (Plate 5).

The Wilson Wetlands are a brackish water lagoon system, which has well-established conservation values. Three lagoons (Wetlands 1, 2 and 3) have been recognised (Figure 1).

Over several decades, the Lagoons have undergone major changes in their hydrology (from brackish to freshwater); as a result of local landuse changes, upstream developments, and freshwater inflows from major, urban stormwater drains.

Plate 5 A view of dense Hydrocotyle infestations in Wilson Wetlands

There has been at least two decades of Hydrocotyle research and management effort documented from the Canning River region (Ruiz-Avila and Klemm, 1996; Swan River Trust, 1996). Given this previous history, and the high degree of interest by the local community in managing Hydrocotyle in the Canning River region, the Hydrocotyle WMP needs to achieve a high level of consensus amongst stakeholders in terms of the way forward.

The Hydrocotyle-infested Canning River area – the main channel between Kent Street Weir and Nicholson Road Bridge and associated wetlands and lagoons are depicted in Figure 1

Kent Street Weir

Albany Highway

Leach Highway

Nicholson Road

Marmot 2

Marmot 1

Marmot 3

Wilson 2Wilson 1

Wilson 3

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX,Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community, Esri, HERE, DeLorme, MapmyIndia,© OpenStreetMap contributors, and the GIS user community

397,000

397,000

398,000

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399,000

400,000

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6,456,

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Figure 1

Job NumberRevision A

23-15602

G:\23\15602\GIS\Maps\Working\2315602_Z008_WetlandsOverview_A4.mxd

Map Projection: Transverse MercatorHorizontal Datum: GDA 1994Grid: GDA 1994 MGA Zone 50

0 110 220 330 44055

Metres

LEGEND

o© 2015. Whilst every care has been taken to prepare this map, GHD (and ESRI) make no representations or warranties about its accuracy, reliability, completeness or suitability for any particular purpose and cannot accept liability and responsibility of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred by any party as a result of the map being inaccurate, incomplete or unsuitable in any way and for any reason.

Date 02 Sep 2015

Perth Region NRMHydrocotyle Management Plan

Canning River Regional ParkWetlands and Lagoons

Data source: GHD, Hydrocotyle/HydrocotyleCover, 7/8/2015; ESRI, World Imagery/http://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer accessed 7/8/2015 Created by:atdickson

20 Smith Street Parramatta NSW 2150 Australia T 61 2 8898 8800 F 61 2 8898 8810 E [email protected] W www.ghd.com

Paper Size A4

DRAFT

Wilson WetlandsMarmot Way Wetlands

Principal RoadMinor Road

Source: Esri, DigitalGlobe,GeoEye, EarthstarGeographics, CNES/AirbusDS, USDA, USGS, AEX,


2. Information Review Effective control strategies for aquatic plants are usually based on a sound knowledge of their biology, ecology and factors that influence the plants’ spread and colonization. Accordingly, the Hydrocotyle WMP needs to take into consideration the key factors, which influence the Hydrocotyle infestations in the region, based on both local research and management experiences, as well as overseas experiences in similar habitat and situations.

These views were endorsed by the Stakeholders during the consultation process and workshops (see Appendix A and Appendix B).

This Section provides an overview of the ecology of Hydrocotyle and management experiences, gleaned from available historical information in the Canning River region, WA and from overseas. Information was obtained from: (a) A review of all available historical reports relevant to Hydrocotyle management and related issues in WA; (b) Consultation with major stakeholders, in face-to-face interviews and phone interviews with individuals and groups; and (c) A global literature search, covering journals and publications.

There is extensive information and documented experiences of Hydrocotyle control from UK and other Western European countries (mainly, The Netherlands, Belgium and Germany), where the species has been of concern for about 20 years. A summary of some relevant information is provided in Appendix B.

The Information Review provides an increased understanding of ecology and biology of Hydrocotyle, as well as methods that have been found to be effective in other jurisdictions and situations. The information immediately relevant to this WMP are summarised below.

2.1 Hydrocotyle Growth attributes and reproductive strategy

In aquatic environments, Hydrocotyle forms floating mats as an emergent, stoloniferous, aquatic plant. However, in moist, lower and upper riparian vegetation, it behaves as a helophyte (perennial marsh plant that bears its overwintering buds in the mud below the surface; from the Greek words: helos – marsh; phyte - plant). The plant possesses a number of characteristics typical of strongly colonising (weedy) species. These include the following:

a. High growth rates, particularly when conditions are favourable (warm temperature; high sunlight; high nutrients);

b. Effective vegetative propagation (new plants arising from even small fragments);

c. Reproduction from seeds; at least 50% of seeds per fruit are viable with little dormancy;

d. Plasticity in growth responses (e.g. over-wintering, aquatic, as well as partly-terrestrial growth forms; increased growth in high nutrient environments);

e. Relatively easy spread by various agents (fragments are known to gain weight and produce roots while floating, and then rapidly grow in new environments); and

f. High resistance to herbivory (McChesney, 1994).

The growth season of Hydrocotyle is the warm months - spring and summer (June and July in the Northern Hemisphere; and October to February in the Southern Hemisphere) and growth typically starts in early spring from small plants or fragments when air and water temperatures rise (Klemm et al., 1993; Ruiz-Avila and Klemm, 1996; Newman and Dawson, 1998; Newman, 2006; Hussner and Lösch, 2007; Newman et al., 2009; Newman and Duenas, 2010).


The life-cycle can be schematically depicted as in Figure 2. Hydrocotyle grows slowly in spring and form small, up to 10 cm2 large leaves (Figure 2a), which mostly float on the water surface. With increasing temperatures, photoperiod and light intensity, leaves grow larger and petioles reach a height of up to 40 cm above water level (Figure 2b) (Webster, 1994; Newman, 2006; EPPO, 2006; CABI, 2015).

The stems root freely from nodes at about 4-15 cm intervals. With decreasing temperatures and light availability in autumn, smaller leaves develop and some of the leaves die due to night frost. At this time, Hydrocotyle will form floating and submerged leaves (Figure 2c). The latter are able to survive the low water temperatures during the winter (Hussner and Lösch, 2007). From these small submerged plants and leafless over-wintering stolons plants will grow out again in spring.

Figure 2 Life cycle of Hydrocotyle ranunculoides (Source: Hussner and Lösch 2007)

There is evidence from Western Europe that natural fragmentation tends to occur, releasing fragments in fast flowing environments, and in the winter; however, both fast flowing water and winter conditions are noted as less suitable for rapid regrowth and re-colonization.

From the information review, the following observations can be made of the biology, ecology and growth conditions of Hydrocotyle:

Many growth parameters, such as leaf area index (LAI), total dry weight, dry weight of leaves, petioles, shoots and roots, total shoot length, number of nodes, total number of leaves and the average leaf size) have been recorded to be much higher in habitat with high nutrient content of the soil, compared with stands in habitats with lower nutrient contents (EPPO, 2006; Hussner et al., 2012; CABI, 2015).

In one of the European studies, which included modelling Hydrocotyle growth, the model (CHARISMA) accurately predicted growth patterns and biomass accumulation in an unmanaged state. The model predictions matched the actual annual biomass production (maxima of approximately 1,200 g dry weight m-2).


The model also suggested that biomass maxima may occur on more than one occasion per year, resulting in peak releases of vegetative fragments on a more regular basis, especially if plant material is cut, releasing fragments at optimal times of the year for regrowth and colonisation (Hussner et al., 2012). However, the study has not been extended to model the effects of management actions.

In Australia, research indicates that Hydrocotyle doubles its biomass in 3 days (Ruiz-Avila and Klemm, 1996). In the UK, doubling times vary between 4 and 7 days in summer, depending on the availability of nitrate, and the plant also exhibits a seasonally variable growth rate with maximum growth in late summer when it typically forms extensive floating mats of vegetation (Newman, 2006). It over-winters in the margins and on banks of waterways, as a much flatter and smaller plant.

Webster (1994) determined seed viability in glasshouse conditions to be about 44% and average seed production (estimate) under favourable conditions to be approximately 8000 seeds/m2. Her studies indicated that only one seed per mericarp was viable, resulting in approximately 50% of seeds being viable.

Klemm et al. (1993) estimated the potential seed production in the field, based on biomass (per m2 of plant biomass) of Hydrocotyle, to be 9000 seeds/m2. Their estimate included immature fruits and seeds, some of which may have aborted. A separate study by Webster (1994), collecting mature Hydrocotyle seeds from mats in the field for 50 hours- yielded only 1600 seeds, which was suggested as a much lower figure than Klemm et al.’s (1993) estimate based on plant biomass.

Webster’s studies (1994) also showed that seed viability and seedling germination were both significantly higher at lower temperatures (15 0C), compared with higher temperatures (23 0C or 28 0C); this was possibly an adaptation of a species of temperate origin (Webster, 1994). Seeds did not germinate in the dark; nor did they grow in water. Seeds grew strongly in muddy substratum. These findings suggest that seeds caught in and under mats of Hydrocotyle would not germinate, but the removal of mats could stimulate new plants from seeds.

Salt affects the growth and survival of Hydrocotyle, as it is essentially a freshwater species. This suggests that salinity management could be a management tool in the Canning River. Preliminary studies in WA by Klemm et al. (1993) indicated the critical salinity levels to be in the range of 4% - 20% sea water. Webster’s studies (1994) indicated the critical range to be 10% to 20% of sea water, and severe impairment of Hydrocotyle growth levels below 10% sea water.

Salinity inhibited Hydrocotyle root growth, leaf production and stunted the vigour of clonal growth; however, the repressive effects of salt depended on the level of salt and duration of exposure. The research conducted in WA (Webster, 1994) indicated varying levels of salt tolerance by clonal fragments and rapid recovery of growth in freshwater. The management implication is that relatively short exposure of a few days to salt water up to 20% sea water is highly unlikely to be sufficient for Hydrocotyle control.

2.2 Management experiences - Overseas

In the UK and several other European countries, mechanical control is the main method of Hydrocotyle management, with cutting and removal of large floating mats. In the Dutch canal systems, mechanical cutting is commonly used, as part of regular maintenance, resulting in a much reduced final biomass.


In the UK, mechanical control has probably perpetuated the presence of the plant at several locations, primarily as a result of the timing of cutting and the release of vegetative fragments at optimum times for regeneration of fragments.

In overseas studies on the comparison between mechanical and chemical costs, herbicides are approximately 50% cheaper than mechanical control, and have also resulted in a better overall reduction in plant biomass in the following year.

Novel techniques, i.e. the use of hydrogen peroxide, flame throwers (heat), adjuvants and combined mechanical and chemical techniques have all been tested in greenhouses studies, and these show considerable promise (Newman et al., 2009).

The prospects for flame weeding have also been positive; as a result, this control option is being investigated in Belgium under practical conditions in the growth season for the optimal timing of application in relation to the growth stages of Hydrocotyle.

Trials using herbicides and adjuvants, in combination with mechanical control, have been on-going in the UK. Much of the research indicates that site requirements and conditions govern the choice of technique and optimisation of those techniques in particular situations requires up to date advice, based on experience.

As reported by Hussner et al. (2012; and references therein), in Flanders, Belgium, provincial and local authorities have collaborated with the Flemish Environment Agency in a monitoring and control program that addressed both water bodies in both public and privately-owned lands. The program aimed to eradicate Hydrocotyle, with the plan consisting of using contractors for mechanical removal, according to a strict protocol, avoiding techniques producing plant fragments, and manual harvesting of all plants remaining after three weeks. Chemical treatment is not allowed in the program. Manual intervention is continued until an infested site is cleared of Hydrocotyle. It has been noted that the efficiency of removal strongly depends on the quality of the work of contractors and good project management. On private properties, initial removal can be carried out at no expense to the proprietor if prospects for success and follow-up by the land owner are good. Results over the past few years appear to be promising.

2.3 A Brief History of Hydrocotyle management in the Canning River and associated waterways

The following is a synthesis of the history of Hydrocotyle infestations in the Canning River regions, gleaned from a review of available literature (Webster, 1994; Swan River Trust, 1996); Ruiz-Avila and Klemm, 1996) and information provided by stakeholders.

In late 1991, there was an estimated 175 tonnes of Hydrocotyle in the Canning River (biomass was calculated, based on aerial photography of the infestation areas and actual biomass determinations and area/weight relationships).

Early control attempts involved a two-week program of physical removal of Hydrocotyle by cutting the floating mats with sickles and scythes from small boats. The mats were then pushed by small boats to an aquatic macroalgal conveyor-harvester, floated to the bank and removed by a backhoe. Follow-up maintenance control was conducted until January 1992, when the growth rate exceeded the rate of removal.

Whilst the physical removal program of 1991 provided short-term relief, it resulted in fragmentation of plant material, which dispersed and regenerated in new habitat, causing Hydrocotyle to spread beyond the original infestation. New mats grew from these fragments over the following 12 months greatly increasing the infestation size.


By September 1992, the estimated biomass in the River was 420 tonnes, mostly in the freshwater sections of the River, above the Kent Street Weir. During the summer, the mats grew rapidly, covering the River from bank to bank. Downstream of the Kent Street Weir, the rise in salinity destroyed all of the mats. The experience and knowledge gained during these early attempts at control proved invaluable in the development of an integrated strategy for Hydrocotyle management in the Canning River regions (Ruiz-Avila and Klemm, 1996).

Stakeholder agencies and the local community were then involved in the complex technical, environmental, organizational, legislation-related, educational and social requirements of developing an integrated management strategy (Klemm et al., 1993). Extensive consultation was undertaken and was regarded as a vital component for ensuring community support for Hydrocotyle management. The aim of the strategy was to eradicate Hydrocotyle in the long-term, whilst minimizing adverse effects on water quality, river ecology, recreational amenities and public health. As part of the strategy, Hydrocotyle was declared a noxious weed in 1992 by the then WA Department of Agriculture.

The lack of biological and ecological information was identified as a key constraint to effectively managing the plant. This led to various research studies being supported and undertaken (see McChesney, 1994; Webster, 1994; 1995). A two part management strategy was developed, which consisted of a short-term control program, implemented in early 1993; and a long-term eradication program.

The short-term strategy relied largely on physical removal, similar to the methods used in 1991, and follow-up treatments with herbicide. About 2,000 tonnes of Hydrocotyle were removed in 1993, with plant matter then composted by the Local Councils. Biological control was not considered as an option; ecological techniques were either unsuitable or unavailable for use in the short-term program, but were recognised as suitable in the long-term strategy of eradication – if other methods failed (Ruiz-Avila and Klemm, 1996).

Round-up™ Glyphosate, a systemic (one that translocates in a plant) but non-selective herbicide, was the herbicide of choice in the early stages, based on the results of glasshouse trials, its low toxicity to mammals, fish and microbes, and low to medium toxicity towards birds and other aquatic life. Initially (1993), an application rate of 360 g/ha (i.e. 1 L of commercial product in 100 L of water per ha) was used. Later, in 1994, a stronger rate commercial product (450 g/ha) was used. Strong community concerns were raised at this time about the overuse of herbicides and potential adverse impacts of other techniques on the riverine ecosystems.

Despite providing a high degree of short-term control, regrowth of Hydrocotyle still occurred after a single round of Round-up™ Glyphosate treatments. This suggested that one round of treatments was not sufficient to eradicate Hydrocotyle. Regrowth was attributed to some material surviving the treatments, establishment from new seedlings and re-introduction of Hydrocotyle from other areas to the treated areas. Subsequent research and monitoring of Bannister Creek treatments by Webster (1994) confirmed that a single round of Glyphosate treatments was inadequate for Hydrocotyle control.

The long-term program included investigating the opportunities for reduction of nutrient loads into the River from the upper catchment and the removal of nutrient-rich sediments from sections of the River. Major waterway health programs commenced in the upper catchments around this time with the aim of reducing nutrient loads in the drainage network.

Nutrient enrichment of the waterways was regarded as a cause of Hydrocotyle’s expansion, and reduction of nutrients would reduce the opportunity for invasion by Hydrocotyle, as well as other aquatic species (Ruiz-Avila and Klemm, 1996).


Responding to public concerns, an ecological investigation was also undertaken to identify whether or not there are environmental impacts of management action on the riverine fauna and their habitat, and to measure such effects. Macro-benthic fauna were measured throughout the management program and areas where control was being implemented with multiple herbicide treatments. The findings (Donahue, 1994) indicated no adverse effects either on water quality, or the communities of benthic organisms, which inhabited the river.

Subsequently, other herbicides were also investigated for use in combination with physical control, and the initial trials involved five herbicides: Chlorsulfuron; Metsulfuron-methyl; Glyphosate, Simazine and Imazethapyr (Klemm et al., 1993).

Previous studies had shown that Hydrocotyle is quite sensitive to salinity levels. Based on this information, an option considered in the long-term strategy was the possibility of manipulation of salinity in the freshwater sections of the Canning River by the removal of the weir boards.

Reporting on the Hydrocotyle management efforts in the Canning River and surrounding areas, Ruiz-Avila and Klemm (1996) concluded that the integrated strategy was successful in controlling the Hydrocotyle invasion with no long lasting environmental impacts.

The lessons learnt were the need for: (1) Broader community/stakeholder consultation; (2) Integration of all appropriate methods; (3) Control of the cause of the weed’s proliferation (i.e. eutrophication); (4) A commitment to long-term involvement to eradicate the weed; (5) Intervention at an early stage, when the weed populations are still small (i.e. 1983); and (6) Understanding the risks of selling and dumping of non-native aquatic plants.

The historical accounts indicated hope that additional biological and ecological knowledge (determining life-history attributes; population dynamics and habitat requirements) of Hydrocotyle would aid in the efficacy of long-term eradication, which may be achieved in the next 5 years. However, the growth of Hydrocotyle in terrestrial environments, noted during that period was also another setback. It was also suggested that the Canning River system requires a long-term rehabilitation program to prevent future problems of aquatic weeds, posed by Hydrocotyle and others (Ruiz-Avila and Klemm, 1996).

2.4 Recent Management Effort

2.4.1 Hydrocotyle Working Group (since 2002)

Several agencies and stakeholders formed a partnership in 2002 in response to the need for co-ordinated control and management of Hydrocotyle across the Canning River regions, tributary creeks, lagoons, wetlands and the associated drainage network.

The group included representatives from the City of Canning, Water Corporation, former Department of Environment and Conservation (DEC, now Department of Parks and Wildlife, DPaW), Swan River Trust (also, now part of Department of Parks and Wildlife, DPaW), Department of Agriculture (now DAFWA) and the local community of volunteers and catchment groups, including SERCUL (Brett Kuhlmann, Matt Grimbly, SERCUL, July 2015, personal communications).

The formation of the group is regarded as an important mechanism for co-ordinated action, discussions of management issues and resolving areas where there have been differences of opinion, due to jurisdictional issues, as well as on-ground implementation of control. Lack of continuous funding for Hydrocotyle management has been a major constraint that the Working Group has had to manage.


During a period of several years, the program was not well funded, and inadequate control led to the re-establishment of Hydrocotyle in many areas that had been previously kept free of the weed by early management efforts. The weed also spread to new locations during this period.

2.4.2 South East Regional Centre for Urban Landcare (SERCUL)

Since 2013, SERCUL has been involved in controlling Hydrocotyle in Mills St Main Drain for the Water Corporation and Collier Pines Drain (Bodkin Park) for the City of South Perth and Water Corporation. The methodology involved initial treatment of the entire infestation to reduce the biomass using a mixture of Round-up Biactive® at 1% and Metsulfuron- methyl at the standard rate of 10 g per 100 L of water.

Herbicide applications were assisted by the vegetable oil additive ‘Endorse’ at 200 mL/100 L. This initial spraying was repeated until the Hydrocotyle reached a level where hand removal became possible. Hydrocotyle colonies less 0.1 m² were easily hand removed; larger patches were subject to repeat herbicide treatments (Table 1).

Table 1 Herbicide treatments at Mill Street Drain and Bodkin Park

Date Volume used

Chemical Area of treatment

22/03/2012 750 L Round-up Biactive (1%) + Metsulfuron-methyl (10 g/100 L)

Whole area of original infestation

28/03/2012 450 Round-up Biactive (1%) + Metsulfuron-methyl (10 g/100 L)





Spot treatments


Spot treatments


Spot treatments







17/01/2014 50 Round-up Biactive (1%) Spot treatments

11/03/2014 220 Round-up Biactive (1%) Whole area of original infestation

8/04/2014 100 Round-up Biactive (1%) Spot treatments

17/10/2014 100 Round-up Biactive (1%) 1st basin



In conducting treatments for Hydrocotyle, control of other exotic vegetation in the Mills Street Drain was also targeted - to prevent Hydrocotyle becoming obscured. According to the monitoring and mapping conducted by SERCUL, the success of the program is evident; no Hydrocotyle has been recorded at either site, since November 2014.


2.4.3 Swan River Trust (SRT) and Department of Parks & Wildlife (DPaW)

The Swan River Trust merged with the WA State Department of Parks & Wildlife (DPaW) from 1 July 2015. At the time of writing this plan, Hydrocotyle, along the Canning River shorelines and riparian zone up to 2 m from the water’s edge was being managed by the DPaW’s Riverpark Unit (John Snowden, July 2015, personal communications).

The department’s Hydrocotyle control program involves regular monitoring by vehicle and vessel of the area from Kent Street Weir to Nicholson Road Bridge. When Hydrocotyle infestations or small colonies are spotted, a contractor is engaged to treat the Hydrocotyle. For the past two years, spot treatments have been conducted using Metsulfuron-methyl at a quarter-dose (i.e. 2.5 g/100 L of water), combined successfully with hand removal of small colonies.

Given below is a brief summary of the Hydrocotyle control program over the last 12 months, which demonstrates the effectiveness of the program:

12/03/2014 Spraying of Hydrocotyle. Swan River Trust areas on the Canning River. Chemical used Metsulfuron-methyl @ 2.5 g/100 L; 2.5 hrs of labour and 15 L used.

26/09/2014 - Spraying of Hydrocotyle. Swan River Trust areas on the Canning River. Chemical used Metsulfuron Methyl @ 2.5 g/100 L. 1 hr of labour and 10 L used.

20/01/2015 inspection by vehicle. Colahan Way Billabong, Camsel Way and Marmot Way. A number of suspect plants noted at Colahan Way and Marmot Way.

26/02/2015 - inspection by vessel. Kent Street Weir to Masons Landing. Small patch 0.5 x 0.5 m removed by hand from an area opposite Richmond St.

6/03/2015 - inspection by vehicle. Colahan Way Billabong, Camsel Way, Marmot Way, Bergall Circuit and Leige Street Wetlands drain.

17/04/2015 - inspection by vessel Kent Street Weir to Masons Landing.

20/04/2015 hand removal - Patch of 2 m2 removed from downstream from Bacon Street boat ramp; 6 m2 patch also on the north side of the river, just past Mason Street;

21/04/2015 - Spraying of Hydrocotyle in Canning River Regional Park area Marmot Way; 10 hrs of labour and 200 L used.; Swan River Trust areas on the Canning River downstream of Masons Landing (Metsulfuron Methyl @ 2.5 g/100 L; 50 L).

14/06/2015 - inspection by foot Masons Landing to Mason Street, north side of the Canning River. Good results noted for areas treated on 21/04/2015.

19/05/2015 - inspection by foot from Nicholson Road Bridge to Masons Landing - No Hydrocotyle recorded.

2.4.4 Wilson Wetlands and Wilson Wetlands Action Group (WWAG)

The Wilson Wetlands Action Group (WWAG), which formed in 1998, has been very active in restoring the Wilson Wetlands’ (brackish water lagoons) environment on the northern side of the Canning River and maintaining healthy wetland systems, which have undergone major changes over decades, as a result of upstream developments.

The Wilson Wetlands and Lagoons are part of the Canning River Regional Park. Hydrocotyle infestations of the Wetlands have been managed by WWAG, which is committed to restoring the wetlands' vegetation through natural processes (WAGG, 2015a). Parts of the Regional Park land WWAG volunteers work on are privately owned by the Trustees of the Christian Brothers (Castledare), who have been supportive of the Group’s commitments and efforts.


As a member of the Hydrocotyle Working Group, WWAG maintains strong working relationships with stakeholders, such as Department of Parks and Wildlife (DPaW), Swan River Trust, as well as with neighbouring community groups (such as Canning River Volunteers and SERCUL), local schools and individuals.

Hydrocotyle infestations within the Wilson Wetlands and Lagoon system are patchy. Most are rooted mats of about 1-3 m2 in extent with loosely floating stolons over water. However, there are also some patches which are quite extensive and greater than 5 m2 of dense mats, deeply-entrenched in slushy mud and in some cases, aggressively spreading across the surface of the lagoons, growing out from beneath the tree-scapes of the Melaleuca rhaphiophylla.

The boggy nature of the Wetland system prevents ready access in some areas, which has resulted in Hydrocotyle infestations becoming entrenched (WWAG (2015a; b). The Group recognises that without active management, Hydrocotyle poses a major threat to the conservation values of the Wetlands, which include habitat loss, due to encroachment and displacement of native species. WWAG is also concerned about poor water quality that may result from decaying vegetation and re-release of nutrients; and potential non-target impacts (i.e. off target damage to native sedges and native flora) that may result from management action, such as excessive herbicide use.

WWAG’s hypothesis is that the growth of Hydrocotyle in the Wilson Wetlands is correlated with the effects of ebb and flow of tidal movements, along with impacts from ground water saline seepages and freshwater inflows through the discharges received from upstream. Given that Hydrocotyle is inhibited by increased salinity, and controlled completely by high levels of salinity, the Group’s efforts are aimed at understanding how these factors can be manipulated to manage Hydrocotyle in the future, using non-chemical methods as tools.

WWAG volunteers undertake control of Hydrocotyle infestations regularly using a combination of methods, primarily manual removal of large biomasses, coupled with timely and measured application of herbicides and fencing to capture fragments from disintegrating infestations. The primary aim of WWAG’s approach is to successfully integrate methods that would reduce herbicide loads required for Hydrocotyle control within the Wilson Wetlands.

WWAG is of the opinion that more field research is needed to understand the ecology of Hydrocotyle and its interactions with environmental factors, such as shade, nutrient-rich sediments, water levels and flows and natural inhibitors. These are elements of ‘site-specific’ management, which would prove useful in future management.

To achieve the objective of better understanding of influential factors, a series of experimental plots have also been established (Russel Gorton, July 2015, personal communications) measuring growth and other attributes of the Hydrocotyle infestations. Some plots are designed to assess the impacts of manual removal and herbicide treatment combinations, and others are for assessing the combination of manual removal and re-planting with native sedges. The plots are located within Wilson 1 Wetlands.

The results of the Trials aim to provide recommendations to all stakeholders as to how Hydrocotyle could be managed in the future without herbicides, or minimising herbicides, but by simply making controlled adjustments to the water levels, and potentially adjusting the Wetlands’ freshwater state to a slightly more saline state, in order to facilitate eradication of Hydrocotyle using natural processes.

Additionally, WWAG aims to develop a better understanding of the correlation between saline and tidal inundation and the influences that these daily incursions may have on Hydrocotyle by conducting regular monitoring of water quality, flows and other influences within the Wetlands.


The Wilson Wetlands and the Canning River are fed by traditional drainage channels from both the Mills St Main Drain and the Wilson lagoon (Wilson 1), which is a freshwater body located directly to the East of Lot 4 and Wilson 2 project area (Figure 7- Appendix D). These two main features of fresh water discharge and mix with the saline influences have major impacts on the capacity of Hydrocotyle to maintain its growth patterns.

There is currently a lack of knowledge as to the exact amount of saline waters, the duration and frequency of saline surges, which are present from both river tides and ground water saline seeps located on Lot 4 of the Castledare Estate that affect the growth and retardation of Hydrocotyle. One of the goals of WWAG’s work is to analyse data collected from the Wilson Wetland (Wilson 2) in Lot 4 over an extended period and link it with data collected from the Department of Waters, Kent St Weir, lower gauging station KSW downstream site 616094

WWAG has successfully attracted funds from the Swan Alcoa Landcare Program, Department of Environment and Conservation, and the City of Canning. This has enabled the Group to engage contractors to undertake additional work that is beyond the scope or qualifications of volunteers, such as herbicide application, and to buy equipment and tools.

The Group has made a recent proposal to the Hydrocotyle Working Group for three years of funding (June 2015 to June 2018) to continue the Hydrocotyle management and wetland restoration works within the Wilson Wetland 2 areas on land owned by the Trustees of the Christian Brothers (WWAG, 2015b).

Further details of WWAG’s activities and approach and a map of the Wilson Wetlands are provided in Appendix D.

2.5 Levels of Current infestations

SERCUL has been assisting the Hydrocotyle Working Group in co-ordinating the management effort in various ways, including undertaking regular inspections and mapping.

Maps on distribution and extents of Hydrocotyle, provided by SERCUL indicate the levels of infestations in 2007 (Figure 3). The main infestations in 2007 were in the Bannister Creek, Mill Street Drain, Wilson Wetlands and in an upstream stretch of the Canning River.

Additional mapping was conducted by SERCUL in May 2015 with a visual assessment of Hydrocotyle infestation densities, based on areas of small, medium or large-sized colonies or populations (Figure 4).

Broadly, the main areas of infestations were in the Wilson Wetlands on the northern side; and two other wetlands on the southern side (adjacent to Marmot Way and Colahan Way); and some upstream reaches of the River around Mason’s Landing.

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© 2015. Whilst every care has been taken to prepare this map, GHD (and ESRI) make no representations or warranties about its accuracy, reliability, completeness or suitability for any particular purpose and cannot accept liability and responsibility of any kind (whether in contract, tort or otherwise) for any expenses, losses, damages and/or costs (including indirect or consequential damage) which are or may be incurred by any party as a result of the map being inaccurate, incomplete or unsuitable in any way and for any reason.


23-15602

Date 02 Sep 2015oPerth Region NRMHydrocotyle Management PlanExtent of Hydrocotyle InfestationSERCUL 2007

Data source: SERCUL, Hydrocotyle/Hydrocotyle2007; ESRI, World Imagery/http://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer accessed 7/8/2015 Created by:atdickson



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$© This map must not be reproduced without the permission of SERCUL69 Horley Road Beckenham WA 6107

T: 08 9458 5664 F: 08 9458 5661E: [email protected] W: wwwsercul.org.au

Program: HydrocotyleProject: Canning River Recovery - HydrocotyleLocation: Canning River Regional Park

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Date drawn: 13/5/15Revision: 1Drawn by: M.GChecked by: M.G

Scale: 1:11,000Original size: A3Imagery from: 15/03/11Source: Nearmap

Hydrocotyle within Canning River Regional Park - Survey 11 and 12 May 20150-1m² Hydrocotyle1-10m² Hydrocotyle

10-20m² Hydrocotyle

20-50m² Hydrocotyle

High Density Hydrocotyle 5.6haMedium Density Hydrocotyle 7.4haLow Density HydrocotyleTypha and other weeds requiring control 11ha


3. Key Issues This Section provides an overview of key issues and factors specific to the proposed approach and future planning recommended for managing Hydrocotyle in the Canning River region.

3.1 An adaptive management approach

Managing an aquatic weed problem such as Hydrocotyle requires an adaptive management strategy, learning from experiences, and making the right decisions for future management. Figure 5 is a schematic depiction of this approach. Further details of the steps involved are given in Appendix C.

Figure 5 Schematic diagram showing the adaptive management approach that underpins the Hydrocotyle Management Plan

An adaptive management approach involves the following:

1. Establishment of realistic management goals and conservation targets for any site;

2. Determining the level of the infestation’s threat to a given location/site and management goals for the site;

3. Determining the methods suitable for application to control the infestation at that site (site-specific weed management);

4. Developing an implementation plan designed to move conditions towards the management goals and to abate threats to the agreed targets;

Establish Weed

management Goals

Identify Conservation

Goals

Prioritise Infestations

and Locations for Weed

Management

Assess Control

techniques suitable for

each site/location or

'cluster' of sites

Develop and Implement

Weed Management

Plan

Monitor and assess impact of

management actions

Review and Modify Plans as

necessary


5. Establishing monitoring and assessment methods, while efforts are being made to arrest the weed’s growth, to monitor the impacts of weed management actions, in terms of the management goals, environmental impacts and target protection;

6. Start the weed management cycle over again by re-evaluating conclusions made in steps 1-4 and modifying, where necessary.

3.2 Negative Impacts of Hydrocotyle

Detailed discussions of negative impacts of Hydrocotyle in the Canning River region have been documented in the reviews conducted by Klemm et al. (1993), McChessney (1994), Webster (1994; 1995) and the Swan River Trust (1996).

A snapshot of likely ‘Triple Bottom Line’ impacts (i.e. environmental and/or ecological; social and economic values) of the Canning River and associated Lagoons and Wetlands affected by Hydrocotyle is given in Table 2.

It should be noted that these impacts have not been quantified to any extent, but have been generally associated with similar aquatic weed infestations in rivers, streams and wetlands, in Australia, as well as overseas.

3.3 Beneficial Uses of Hydrocotyle

Aquatic plants are well known to absorb nutrients, either from the water column or from various substrata and build biomass. In USA, this aspect of utilization has been studied. The high rate of productivity of Hydrocotyle was useful in removing pollutants in livestock effluent (Boyd and Banes, 1988). Hydrocotyle was noted as particularly useful, because it was not killed by the low winter temperatures. The Hydrocotyle harvested from treatment ponds could then be used in methane production, and possibly, as animal feed (McChesney, 1994).

3.4 Stakeholder and Community Engagement

Stakeholder and community engagement is considered integral to achieving successful long-term weed management outcomes. The stakeholders and the community are important in the process of identifying waterways values and risks through to the development and ownership of the management strategies during the implementation of the plan.

‘Stakeholders’ include a range of individuals and agencies that may have an influence on or be influenced by the protection of the Middle and Upper Canning Estuaries. They include local authorities, Government bodies, community organisations and industry bodies, and most are participants in the ‘Hydrocotyle Working Group’.

Fostering community participation at all stages of developing and implementing the Hydrocotyle WMP helps to build trust between community members, institutional stakeholders and project teams. It also provides the community and institutional stakeholders with easy access to information about the weed management approach, resources spent, actions implemented, and achievements, over time.

In developing the Hydrocotyle WMP, a Stakeholder Engagement Strategy was developed and implemented to ensure that effective stakeholder engagement activities were undertaken throughout the preparation of the WMP.

The Strategy provided a framework that ensured a guided, proactive approach when considering community and institutional stakeholders and fostered open communication between the community members, institutional stakeholders and the project team.


Table 2 Triple Bottom Line Impacts of Hydrocotyle*

Ecological/Environmental Values Social (Cultural Values and Public Health)

Economic Values

• Water quality – Dense, floating mats could deplete waterbodies of oxygen by reducing turbulence and wind-based mixing at the surface, inhibiting gaseous exchange between ambient air and water. Oxygen depletion could also occur through negative effects on phytoplankton and other submerged aquatic plants, through shading. Modification of water quality could affect ecological health and biodiversity in infested waterways;

• Physical obstruction - Large infestations may reduce or change the available shelter and breeding/nursery habitats for aquatic species; negative impacts on Waterbirds (diving) were noted when large infestations reduced the open water area;

• Basking sites may be reduced for tortoises; physical barriers posed by dense mats and rafts may be problems for other fauna; Large infestations may reduce the shelter and breeding habitat for terrestrial fauna, in an otherwise over-cleared landscape;

• Modified aquatic habitat may favour other exotic, aggressive species over native species (i.e. Mosquito Fish – Gambusia holbrooki);

• Large infestations may modify or alter the existing functioning of aquatic ecosystems – i.e. storing and re-cycling nutrients; and food web interrelationships;

• Modify the processes of absorbing, trapping, and detoxifying toxicants and pollutants, currently occurring in Lagoons and Wetlands;

• Impede or modify natural drainage (i.e. tidal influences), and movement of urban runoff through creek systems and ditches;

• Potential degradation of foreshore areas, resulting from erosion, sedimentation and loss or modification of riparian areas;

• Potential loss of water from some habitats, due to higher evapo-transpiration from dense infestations, compared with normal surface evaporation.

• Reduced opportunities in areas popular for public recreation, (i.e. fishing, boating and swimming);

• Continuous mats prevent animals from drinking directly from the River;

• Water flow into upstream irrigation pipes may become obstructed;

• Restriction of opportunities for community-based environmental activities in affected areas within Canning River Regional Park, because of potential to cause further spread;

• Potential impediment of drainage and water flows in the upper sub-catchments in heavy wet weather, which may cause local flooding

• Potential public health risks due to changed conditions providing breeding opportunities for mosquitoes or snails, who carry human parasitic disease-causing organisms

• Decreased River based tourism, (which is a key focus of the local economy);

• Diminished values of urban developments in key centres of Perth and its southern suburbs;

• Reduction in values of local water-front properties and vistas of high value;

• Increased waterways maintenance and management costs.

*Sources: Klemm et al., 1993; McChesney, 1994; Webster, 1994; 1995; Ruiz-Avila and Klemm, 1996; Swan River Trust, 1996; Newman et al., 2009; Newman and Duenas, 2010; Hussner et al., 2012; CABI, 2015


3.5 Management Principles and Strategic approach

Weed management issues are particularly complex within Australian waterways, as there are multiple users of water, as well as conflicting environmental and institutional objectives in managing aquatic weed problems.

There are also differences of opinion on management approaches (i.e. containment vs. eradication; non-chemical methods vs. use of herbicides; effectiveness of various approaches and their realistic applicability; and concerns related to environmental and water quality impacts).

Adopting the following principles of strategic weed management is necessary to achieve successful Hydrocotyle management in the specific waterways in question, and more broadly, in the larger Canning River region:

1. Prevention and early intervention are the most cost effective techniques that can be employed to manage Hydrocotyle and similar aquatic weeds. The spread of new infestations can be minimised (or avoided) through managing environmental conditions and the movement of viable weed material (i.e. fragments of stolons or rhizomes and seeds) along natural and artificial waterways, drainage lines and riparian edges.

2. The primary responsibility for weed management rests with land-owners and delegated land managers, but collective action is necessary where the problem transcends the capacity of the individual landholder or institution to address it adequately. Land-owners require the knowledge and mechanisms for responding to weed incursions on their land and to undertake monitoring and follow-up works as required.

3. Successful weed management requires a coordinated approach involving all levels of government in establishing appropriate legislation; educational and coordination frameworks, in partnership with industry, land-owners and the community. A key tenet in this approach is to facilitate communication that implements strategic weed management planning and on-ground action throughout the Swan and Canning River Regions.

4. Weed management is an essential part of the sustainable management of natural resources and the environment. As such, it requires an integrated, multidisciplinary approach, which includes both direct action against a problem species; and indirect action against contributory factors (e.g. introduction of non-native species to new environments; flow modifications in waterways that cause changes in hydrologic regimes, reducing nutrient enrichment and contamination of waterways by urban pollutants).

Adopting the above principles and approaches provides a comprehensive, strategic approach and basis for the Hydrocotyle WMP.

3.6 Other key Issues

3.6.1 Sites of specific Conservation value

Canning River Regional Park

As a major river, draining through an increasingly urbanised part of Perth, the Canning River’s shorelines and riparian zones have high conservation and biodiversity values. The protection of the riverine areas and their integration into public appreciation of nature, and for recreational pursuits are well established through the Canning River Regional Park. In 1983, the Regional Park, along the Canning River, was identified as having ‘…the best estuarine vegetation of the Canning and Swan Rivers; and supporting 85 species of birds…’ (Klemm et al., 1993).


The significant nature reserve comprises remnant vegetation, bushlands and parkland areas and includes historic sites, such as Woodloes Homestead, Mason’s Landing and the Kent Street Weir. There are picnic areas at Riverton Jetty Reserve, Wilson Park and Masons Landing. A number of nature trails meander through Eucalyptus rudis woodlands, and several wetlands and lagoons provide high-value recreational opportunities with abundant native fauna and flora, including a variety of birds, frogs, turtles, insects and plants.

While the Canning River Regional Park has undoubtedly high ecological values and is a popular recreation area, it is at the same time beset by a number of critical management problems such as outbreaks of Cyanobacteria (blue-green algae), and the aquatic weed Hydrocotyle, the occurrence of fire, widespread invasion of various other weeds and areas of degradation and vandalism. Most areas of the Park are managed by the Department of Parks & Wildlife (DPaW)

Wilson Wetlands and other Lagoons

As shown in Figure 4, there are several Lagoons and Wetlands of high conservation value associated with the Canning River. The lagoons on the northern side (Wilson Wetlands 2 and 3) are largely brackish water, while Wilson Wetlands 1, receiving drainage from the urban developments to the north, via the Mill Street Drain and Wilson Drain are largely freshwater.

Appendix D provides an overview of Wilson wetlands.

3.6.2 Nutrients in waterways

Nutrient enrichment (‘eutrophication’) is one of the most important factors contributing to the degradation of water quality of waterways, lagoons and estuaries. In natural systems, phytoplankton and submerged aquatic plant growth is often limited by one or more dissolved nutrients (mainly, nitrogen, N and phosphorus, P), or other factors, such as sunlight availability. However, for a species like Hydrocotyle - rooted in shallow, slushy mud; largely emergent and with floating rafts of stolons and runners bearing roots at nodes, nutrients are unlikely to be limiting in most aquatic habitats. Such plants are able to obtain plant growth nutrients mostly via the root system, or from the water column, through the fine roots at nodes.

Most aquatic weeds respond to nutrient enrichment of waterways with luxuriant uptake and growth, leading to extensive biomass production (Sculthorpe, 1967). This is the case with Hydrocotyle, as documented in Western Australia, and overseas (Ruiz-Avila and Klemm, 1996; Swan River Trust, 1996; Hussner and Lösch, 2007; Newman, 2010). Many growth parameters, such as leaf area index (LAI), total dry weight, dry weight of leaves, petioles, shoots and roots, total shoot length, number of nodes, total number of leaves and the average leaf size) have been recorded to be much higher in habitat with high nutrient content of the soil, compared with stands in habitats with lower nutrient contents (EPPO, 2006; Hussner et al., 2012; CABI, 2015).

Nutrient reduction is considered a long-term strategy to improve the Canning River system (Swan River Trust, 1996, and references therein). There are major programs in the Canning River sub-catchments, targeting local waterway health improvement, being implemented with collaboration from various State and Local government agencies and community groups (SERCUL, 2014). However, reductions of nutrients in the infested waterways may only alleviate Hydrocotyle growth in some situations, but not provide control of the species. This is because most clonal, aquatic species, reliant on vegetative growth and reproduction strategies, are capable of prolific growth even in oligotrophic (low nutrients and high levels of dissolved oxygen) systems (Sculthorpe, 1967).

Many of the historical reports from WA (Webster, 1994; 1995; Swan River Trust, 1996, and references therein) acknowledge that reducing nutrients in the waterways is not a viable option for Hydrocotyle management in the Canning River region.


Nevertheless, reducing nutrient loads is likely to have the effect of limiting both un-balanced phytoplankton growth, and nuisance aquatic plant growth, because it creates conditions for a wide array of native species to establish and thrive (i.e. increased biodiversity).

3.6.3 Vehicles of Spread

An understanding of the vehicles of spread is important in assessing the risks of spread from infested locations and for prioritisation of sites for management. Modes of Hydrocotyle spread include transport in floods and heavy wet weather flows, utilisation of materials contaminated with the weed, inappropriate weed management practices and inappropriate disposal of material contaminated with fragments of the weed.

Natural (non-biotic) dispersal by water occurs within contiguous systems, once the plant has become established by other means. Transport by water (either stormwater or flooding in heavy wet weather) is not thought to be responsible for introduction of Hydrocotyle into new areas that are isolated from existing populations.

Vector Transmission (biotic) – No specific vectors have been confirmed, although birds may roost on large mats (as has existed before in the Canning River) and may transport fragments to other locations.

Equipment - Transport on machinery used to clear watercourses, drains and ditches may be a factor in localised spreading.

Recreational vehicles – Spread by recreational vehicles, such as boats, kayaks and other water crafts is likely in areas that are heavily infested.

Intentional introduction – Hydrocotyle has been intentionally introduced as an ornamental tropical aquarium plant in most countries, including Australia, UK, Western Europe and parts of Africa. The majority of sites where the species occurs outside its native range are thought to be the result of deliberate introductions by the aquarium trade.

Accidental introduction – In countries or regions where Hydrocotyle has been introduced as an aquarium plant, the species is likely to be introduced locally into waterways following cleaning of aquaria and ponds.

3.6.4 Prioritisation of sites for management

The following three key factors influence the prioritisation of areas for Hydrocotyle control:

The potential for further spread within or beyond an infested area;

The extent of the impact of on-going infestation;

The feasibility of achieving the desired outcomes for a given management area.

Management units can be established and compared according to a relevant set of criteria for each factor, which are assigned scores. A combination of (weighted) scores can be used to determine priority rankings. Special attributes of an assessable unit can also be considered and recorded to explain the rationale for the assigning of any individual score. A Priority Score can be derived for each principal factor as follows:

1. Potential for Further Spread (PFS) - a score of 1-5 derived by averaging the 1-5 scores for terrestrial and aquatic spread, both within and neighbouring management units;

2. Consequence of Further Impact (CFI) - a score of 1-5 for the likely impacts on the ecology and biodiversity within the management unit;

3. Management Feasibility (MF) - a score of 1-3 representing the likelihood of effectively managing or containing infestations within the management unit.


The scores for the three categories are then combined using the following formula;

Priority Level = (PFS + CFI) X MF

This results in a score between 2 and 30, which can be aggregated to levels of priority, such as: Low, Moderate, High, and Very High.

1. The scores for Spread and Impact are based on both degree and likelihood, as shown in Table 3 below. The degree is scored as: minor, moderate or major; and likelihood as: likely, possible or unlikely. Spread and impact are considered in terms of a ‘no action’ alternative. In the case of spread, this assessment process needs to cover both terrestrial and aquatic spread.

Table 3 Scoring System for assessing spread and impact

Degree Likelihood 1. Minor 2. Moderate 3. Major 3. Likely/certain 3 4 5 2. Possible 2 3 4 1. Rare/unlikely 1 2 3

Key decision points for consideration in allocating each of the degree and likelihood levels for spread, impact and feasibility are provided below.

Potential for Further Spread via vectors – aquatic or terrestrial

Minor - Core or low catchment units with little chance of further spread within; and little chance of further spread to neighbouring areas; or neighbouring areas already infested;

Moderate - Marginal or medium catchment order units; core or low catchment order units with some potential for major further infill of unit or spread to less infested units;

Major - Outlier or high catchment order units; units with infestations confined to single site; large potential for spread to other units

Likelihood

Aquatic vectors- consideration of the presence of vectors in management unit, relative to infestations, e.g. watercourses, spread related activities (fishing, boating, channel maintenance, dredging), floodplain areas; consideration of infestation types.

Terrestrial vectors- presence in management unit and relative to infestations of vectors of aquatic spread, e.g. turf farms, regular earthmoving; consideration of infestation types.

Consequence of Further Impact

Minor- little or no significant, at-risk biodiversity assets within the region.

Moderate- Presence within the region at risk biodiversity assets of state significance (Endangered Ecological Communities, EECs; Threatened Species, State Significant Wetlands etc); direct, current impacts or threats to regionally or locally significant, at risk biodiversity assets (e.g. significant species/communities, rivers, wetlands etc).

Major- Direct and current impacts or threats to state significant, at-risk biodiversity assets; presence of nationally significant biodiversity assets (EPBC listed entities, RAMSAR wetlands etc) within the management unit.

Likelihood- vulnerability of type of ecosystem or entity at risk to impacts from Hydrocotyle, including likelihood of Hydrocotyle establishing healthy population and susceptibility of entity to impacts from invasion by the weed.


Management Feasibility

Management feasibility can be recorded as a score from 1 to 3, based on the likelihood of effectively managing or containing infestations within the management unit. The levels of likelihood are the same as those for assessing spread and impact.

Likelihood- the extent to which management or containment of infestations within the management unit could be effectively carried out; Need to consider extent and situation of infestations and effectiveness of available control options. Where spread scores are high, feasibility of containment should be considered; and where impact scores are high, feasibility of mitigation of the relevant impacts should be considered.

Applying a risk assessment framework to the sites means that sites/river reaches can be prioritised for future management, and the options for each site carefully considered, discussed and documented.

With the above approach, vehicles of spread can be clearly identified, with options for future management via administrative procedures (i.e. protocols for weed hygiene), education (public campaigns and signage), etc.

3.6.5 Co-ordination of Management actions

Most weeds, especially aquatic weeds, do not respect geographical boundaries, or man-made, jurisdictional boundaries. Aquatic weeds are a special category because they are transported by floods and water and are able to move widely across different landscapes and jurisdictions.

In implementing aquatic weed management programs, co-ordination of actions by different stakeholders is essential, because if some jurisdictions do not take appropriate action, it could lead to failures in implementing a holistic program, across a broader catchment. The ‘Hydrocotyle Working Group’, with representation from all key stakeholders is an ideal model to successfully implement the Hydrocotyle WMP.

Co-ordination by a central group allows the opportunity to be effective across jurisdictions in terms of collective planning, sharing of resources and effective action on the ground. It also allows any issues or constraints to be resolved via discussions and mediation.

3.6.6 Funding and resourcing

A continuous and longer-term commitment is necessary for successful management of aquatic weeds, such as Hydrocotyle. This requires adequate on-going/follow-up funding for implementation of a Weed Management Plan until the weed occurrence is deemed negligible.

3.6.7 Public Education and awareness

A successful Hydrocotyle WMP requires a long-term commitment to community awareness and education. Once an aquatic weed problem is ‘solved’, most people tend to forget how costly and difficult the management program was.

Education should cover stakeholder agencies as well, so that a better understanding of elements of the management program is achieved.

Most areas, such as Canning, are also prone to new residents moving in; newcomers to an area may not have the same experiences and awareness as those who were there when the initial problem existed. Far too often, stalled educational and awareness campaigns have contributed to the re-occurrence of aquatic weed problems in urban waterways.


Educational campaigns are also important to let the community know why activities, such as on-going, maintenance control of aquatic weeds, are necessary over a longer time frame. In making the Hydrocotyle WMP successful, it will be important to continue explaining the Management Plan and its implementation to the community – either via educational meetings, display of posters with photographs and videos, websites publications, newsletters or other media.

Conducting periodic surveys of the community to gain their impressions of the effectiveness of the program is also an important component. Periodic surveys assist aquatic plant management programs by determining if the needs and desires of the community have changed.

As noted in Hussner et al. (2012), in the Netherlands, a website dedicated to H. ranunculoides has been created, primarily aimed at water utilities and researchers, which provides up to date information on identification, distribution and control options. Likewise, a brochure with general information has been produced to inform stakeholders of the management of waterways.

The Belgian Federal services for Public health, Food safety and Environment and the National Biodiversity Platform launched an information campaign on alien species, which also focused on Hydrocotyle. Raising awareness at national, provincial and local level has involved distribution of free brochures and information sheets among stakeholders, adding warnings to their internet sites, organising information and training sessions and contributing to meetings of professional organisations and interest groups.

Other educational and awareness creation initiatives in Western Europe on Hydrocotyle have involved reviews and overviews published in popular and semi-professional journals, and issuing press releases, targeting nature conservationists, farmers and water managers, as well as enhancing awareness on invasive plants, focusing in particular on the horticultural curriculum and the development of codes of conduct for professionals.


4. Hydrocotyle Management Options The following Sections provide discussions on the management approaches for aquatic weeds, including Hydrocotyle, in Australia, and overseas - that are relevant to developing the Hydrocotyle WMP.

4.1 Strategic Weed Management

Weed management in Australian landscapes (bushlands, catchments and waterways) requires a strategic approach that integrates (1) prevention, (2) eradication, (3) containment and (4) asset protection control activities, at times and places that make them the most effective and efficient. The most effective and efficient combination of techniques depends on factors, such as the biology of the particular weed, and the ecology and circumstances under which it is growing.

There is also recognition in Australia that weed management is all about tackling weed problems, not simply at the individual, local infestation level, but also at other scales, such as the management unit (e.g. conservation reserve, wetland, native vegetation remnant), catchment, landscape, waterway and the region as a whole.

Strategic weed management encompasses the following considerations:

Integrated weed management options – physical methods (i.e. manual and mechanical control), non-chemical methods (i.e. use of heat, steam and/or flame; manipulation of water flows, water levels, lake drawdown; salinity management); cultural methods (i.e. re-vegetation; shading; weed matting; competitive planting); chemical control; and biological control (i.e. use of natural enemies);

The ecology and biology of target weed species, including factors, such as the soil seed-bank, seed longevity, requirements for germination and establishment, vegetation reproduction methods and propagules (i.e. rhizomes, tubers, bulbs, corms, stolons, runners, turions etc.), fragmentation of vegetative parts, and the plant’s life span;

The extent of the overall infestation and the density of populations;

The economics and feasibility of control; and

The nature of the invaded environment, including that of non-target vegetation; as any control technique has potential side effects on the native flora and fauna.

It is generally thought that in implementing a weed management strategy, the positive benefits achievable for biodiversity and other assets must be more desirable than the effects of the weed itself. However, as in most countries, Australia lags behind in thorough investigations of the consequences of different weed management regimes upon biodiversity.

Approaches to weed management are mostly judged by how well they affect the targeted weeds and meet the agreed weed management goals.

4.2 Integrated Weed Management (IWM)

The national approach to weed management in Australia encourages the integration of optimal combinations of concordant weed control options to manage weed problems strategically and in an ecologically sound way. This approach does not preclude any single method, including the use of approved herbicides in or around waterways at recommended rates.


The integrated approach, widely accepted in Australian States and Territories, as well as overseas, promotes prevention as a first step, and then management or maintenance control with suitable combinations of methods, provided the ecological, economic and social impacts of infestations can be minimised or reduced to an acceptable level.

4.3 Factors affecting choice of control methods

The following Sections provide a discussion on Hydrocotyle management options and factors influencing the success of those management methods, from both experiences in the Canning River and associated waterbodies, as well as similar situations overseas.

A number of factors influence the choice of weed management technique applicable to managing Hydrocotyle. These are related to the uses of water, specific landscape situation of the waterway or waterbody, and other considerations, such as community expectations and environmental impacts.

4.3.1 Uses of water

Certain weed control options may not be compatible with the uses of a waterway or waterbody, because of potential downstream impacts. Water from the Canning River regions under consideration is largely managed for its environmental value and recreational use. Some water from the areas upstream of Kent Street Weir is abstracted for irrigation water supplies and other uses may include offtakes for minor, industrial uses. Other uses of water, such as for human and livestock use, are not considered relevant.

Uses of water downstream of an intended herbicide application, or a mechanical weed control operation, which may increase turbidity, may not be suitable for a given purpose. However, such effects are influenced by dilution by mixing, flow rates and distance between site of weed control action and the abstraction point of a particular use of water. Given the current distribution and extents of the Hydrocotyle infestations in the affected areas, large-scale management interventions and impacts on water uses are highly unlikely.

4.3.2 Levels of Control

Aquatic plant management usually involves ‘doing something’ in the waterbody or waterway to correct the problem. With Hydrocotyle, the community of Canning River stakeholders and the public have indicated that ‘doing nothing’ (No Control) is not an option for all areas affected.

Whilst ‘No Control’ is not an option, it is important to consider the possible, as well as probable consequences to the water asset - if different levels of control action is taken against the existing Hydrocotyle infestations, discussed below:

(a) Low Level of Control – Low-intensity control efforts are important to remove an aquatic weed problem, while protecting conservation values, particularly, high-value fish or fauna breeding habitat, and valuable, native aquatic vegetation. Low intensity control may be implemented to achieve the same goals of containment and/or eradication, but over a longer time period, using a combination of low-impact techniques.

(b) High Level of Control – Certain situations may require aggressive control; these include upstream areas in sub-catchments, and infested drainage canals and ditches, which contribute heavily to downstream spread.

The levels of control to be achieved - over what time period, using which combination of methods at given infested sites - are issues that require careful consideration. Often differences of opinion may exist, because individuals, groups and management agencies place different values on the assets they are committed to restoring and protecting.


In some cases, selective control from a given area may be desirable, instead of attempting complete eradication of the problem species within a short period, with potential high impacts. Localised and selective control is an approach that allows community expectations to be managed, without compromising the overall management objectives, particularly when there are unknown factors at play.

In this case, some examples of ‘unknown factors’ are the levels of Hydrocotyle control achievable by non-chemical methods, such as the integration of manual removal with re-planting; and the control achievable by variable salinity levels in the brackish water lagoons, such as Wilsons Wetlands 1 and 2, and other wetlands.

Other examples of unknown factors include the potential environmental impacts of using herbicides, such as metsulfuron-methyl or Roundup Biactive® – even on a small-scale, on sensitive aquatic ecosystems.

4.3.3 Environmental impacts of management action – potential and actual

In general, the larger a weed clearance and control operation is, the greater the environmental impacts. Effects of deoxygenation of waterbodies on desirable aquatic fauna (macro-invertebrates and fish, in particular) are a well-known undesirable effect of aquatic plant management, particularly, submerged aquatic plants.

Deoxygenation could occur as a result of death and decay of large biomasses of aquatic plants and decomposition of organic matter (consuming oxygen); however, oxygen depletion depends on the methods used, and is highly unlikely to be a factor in the control of a surface mat-forming species, such as Hydrocotyle.

There are potential environmental impacts of herbicides, both on flora and fauna; however, effects depend on dose rates, how and where the chemicals are used, as well as frequency of use. It is well known that potential undesirable effects of registered chemicals could be further mitigated by other controls (i.e. limited volumes and infrequent use; and integration with other control methods, etc.).

4.3.4 Public perceptions

There is typically a high degree of concern among the public about the use of herbicides in and around waterways, despite various controls of chemical use. The over-whelming preference of the public and the communities affected is non-chemical control of Hydrocotyle. However, stakeholder and public trust can be obtained by a well thought through WMP.

Instead of antagonism, a well-informed public may accept a compromise between weed control efficacy and realistic achievements of a committed and well-coordinated weed management program, which would achieve the desired levels of control.

4.4 Non-Chemical Control Methods

The following Sections provide some relevant discussions on non-chemical methods that may be applicable to managing the Hydrocotyle infestations at the existing, infested locations. The methods are also important to prevent future infestations in the region.

4.4.1 Prevention

Preventing the introduction of non-native species, such as Hydrocotyle ranunculoides, is regarded as a critical element of management. This can be achieved through legislation (declaration of prohibited species), and education and awareness programs that target the aquarium industry and broader community.


The legislative requirement for declaring Hydrocotyle as a pest plant species has been fulfilled in WA, and broadly, in Australia (see later, in Section 5.4). This precludes the planting, distribution, sale, causing dispersal and spread, or otherwise cause to grow the plant throughout the state of WA. However, regular inspections of aquarium trade websites appears essential to succeed in preventing further sales in the future.

In recognition of the problems caused by Hydrocotyle ranunculoides in the UK and the Netherlands, the European Plant Protection Organisation (EPPO) placed the species on the A2 Action list in 2005 and considers it a quarantine pest (EPPO, 2006). In addition, EPPO requested all European countries to conduct a Pest Risk Analysis on the species.

While recognising the potentially invasive behaviour of H. ranunculoides, the European Food Safety Authority (EFSA) Scientific Panel on Plant Health (EFSA, 2007) pointed out that such behaviour does not occur throughout the region and concluded that the key factors determining invasiveness are insufficiently identified in the Pest Risk Analysis submitted by EPPO (2006) to justify actions across Europe at the European Community (EU) level.

In the Netherlands, sale and possession of H. ranunculoides has been prohibited since 2001 (EPPO, 2006) and a covenant with the private sector aims to prevent further distribution. In the UK, the Royal Horticultural Society prohibited this plant due to its high invasiveness. Possession, sale and distribution of the species are also prohibited in Ireland, Switzerland and Germany. In Belgium, the Hydrocotyle is on the national black list of invasive species and legislation is in place banning its commercial use and distribution (CABI, 2015).

4.4.2 Early Detection, Rapid response and Eradication

Given the history of spread of Hydrocotyle from small, local colonies to extensive infestations (discussed by Webster, 1996), management plans and resources should contain sufficient information and knowledge to identify the weed and areas where there is potential for spread. Trained personnel must be available to conduct regular scouting to efficiently detect any small colonies or populations within targeted areas. This requires training of staff and allocation of adequate resources for a period of time, possibly, up to five years.

Engagement and interactions with NRM officers or Weed Specialists and volunteers in neighbouring areas (i.e. Swan River in the north, and other areas upstream of the Canning River) on a regular basis will help in early detection. If and when new colonies are spotted, an immediate eradication response should be undertaken, followed by monitoring.

It should also be noted that in applying best-practice Australian approaches to early detection and rapid response, herbicides are not precluded. Spot treatments with an aquatic registered herbicide, or a permitted application of a suitable herbicide, can be an integral part of a rapid response to eradicate newly discovered weed colonies and address a larger threat the weed may pose.

4.4.3 Physical Control - Manual Removal

There is ample evidence from both West Australian research (Klemm et al., 1993; Webster, 1994; 1995; Swan River Trust, 1996 and references therein) and from overseas (Newman and Dawson, 1998; Newman, 2006; Newman et al., 2009; Newman and Duenas, 2010; Hussner et al., 2012; CABI, 2015) that manual removal is highly effective and applicable in many locations where Hydrocotyle infestation levels are low to very low.


A few plants or a few colonies can be easily removed in soft mud, and a high degree of success has been demonstrated in Wilson Wetlands, Bannister Creek and Canning River riparian areas. However, for good results, repeated manual removal of any remaining plants after an initial removal is essential and has been successfully conducted (Matt Grimbly, SERCUL; Matthew Box, City of Canning; John Snowden, Swan River Trust, personal communications).

Slightly larger infestations (several square meters) have also been successfully removed by hand in Wilson Wetlands (Russell Gorton, WWAG, personal communications). This is possible in situations where Hydrocotyle is largely in floating mat form of a single layer, with some rooting. However, manual removal always runs the risk of fragmentation and ready establishment of new colonies from the fragments; hence, the infested locations need to be under surveillance for some time after any such removal.

In the Wilson Wetlands, WWAG has conducted trials where manual removal has been integrated with other methods such as herbicide application and/or replanting Hydrocotyle free areas with native sedges. Both approaches have shown considerable promise in the past six months (see Appendix D for a synthesis of WAGG’s work on Wilson Wetlands).

4.4.4 Physical Control - Mechanical Removal

It has been well established overseas that rafts of Hydrocotyle can be cut with weed cutting equipment, buckets or boats. It is acknowledged that mechanical cutting and removal will only offer a very short-term reduction in the local extent of the plant, as Hydrocotyle is capable of growing back rapidly from single nodes. Re-cutting several times appears to be necessary throughout a growth season. However, without thorough removal of all cut material, the inevitable downstream spread of the plant by water cannot be contained easily without barriers.

Where cutting is deemed appropriate, such as in a flowing water canal or drainage ditch, the affected areas should be carefully fenced and netted off (several nets at downstream locations) to reduce the risk of downstream infestation and ensure cut plant material can be removed from the water body.

Mechanical removal is now widely practised in the UK, Netherlands and other European countries to reduce the biomass for subsequent chemical treatments and to ease access for herbicide application, especially in dense masses (Plate 6). Hydrocotyle biomasses of 70-80 kg wet weight/m2

have been mechanically removed in the UK (Appleby, 1997).

Plate 6 An infestation in a canal in UK –removed by mechanical equipment (Source: Newman, 2006)


Mechanical removal to remove as much of the plant biomass as possible, followed by hand picking the remaining fragments four times a year during the growing season is now the accepted practice in the UK (CABI, 2015). This technique has eradicated Hydrocotyle from the upper reaches of the River Chelmer and the River Lee (Hussner et al., 2012).

According to Hussner et al. (2012 and references therein) the European experience confirms that removal is more difficult and labour intensive for stands that are extensively anchored in mud than for floating rafts and carpets, and suggest that, at least in some conditions, post treatment over two years may suffice.

In the Netherlands, mechanical control methods are used with varying success to remove H. ranunculoides from infested waters. For good results, repeated manual removal of remaining plants afterwards appears necessary (CABI, 2015).

Mechanical removal has some application for the management of Hydrocotyle infestations in the Canning River region. The use of mechanical equipment, such as medium or small-sized excavators with tracks, could be useful in accessing infestations, particularly in the periphery of the Canning River Lagoons and Wetlands. Mechanical equipment use appears essential to access Hydrocotyle infestations interspersed among large stands of Typha at several locations in the lagoons. The boggy conditions have prevented access to such infestations without compromising safety to workers.

The use of small, amphibious crafts, such as a ‘Truxor’ (Plate 7) would allow access tracks to be cut through Typha stands with relatively low environmental impacts. The same machines can aid in lifting floating mats of Hydrocotyle off the water, where accessible, without damage to native trees. The Truxor can provide an effective and efficient way of accessing and controlling aquatic weeds in waterbodies, marsh areas or riverbanks by cutting, harvesting and depositing weeds for later collection and disposal. As stated on the Website (http://www.truxor.com.au/) with its low impact ground pressure, the Truxor is ideal for use in sensitive areas were damage is able to be kept to a minimum.

Plate 7 Amphibious crafts ‘Truxor’ used for mechanical removal of aquatic plants (Source: Australian Catchment Management Website, 2015)

4.4.5 Cultural control – Shading

Hydrocotyle can create large mats when there are sufficient nutrients in the water and when roots can access sediment-borne nutrients (e.g. shallow water and shorelines). Experience from overseas is that Hydrocotyle does not establish well in shaded conditions, and shading can be a tool to suppress mat size and density, if there is adequate shoreline shade from trees.

http://www.truxor.com.au/


Although shade may be an effective method of control, it is unlikely to be practical to implement on large, open water bodies, such as the Canning River and Wilson Wetland 1, in which Hydrocotyle has the capacity to form large infestations, which extend across water.

In reviewing the available research (Swan River Trust, 1996), it was pointed out that Hydrocotyle can tolerate low light conditions quite well under the shade of riparian trees and vegetation. Increased shading provided by riparian vegetation along the Canning River, resulting from gradual riparian rehabilitation, may not inhibit Hydrocotyle growth. The strong growth of Hydrocotyle in meandering water channels through large Typha stands in locations such as the Wilson 2 Wetlands also indicates that diffuse but diminished sunlight may be sufficient for the plant’s growth (Russell Gorton, WWAG, July 2015, personal communications).

However, direct placement of shading material (shade cloth or similar) over small-to-medium sized Hydrocotyle rafts is likely to reduce the vigour of a colony or population, allowing it to be later reduced by manual or other means. Therefore, shading, as a technique, has application in areas deemed particularly sensitive, or where other methods may cause non-target effects.

4.4.6 Cultural Control - Use of Competitive plants

Competition from other species – either for physical space and resources, or through chemical interactions (Allelopathy) - can be part of an overall ecological approach to managing weeds, as competitive plantings are known to displace weeds under some circumstances.

Ecological theory indicates that species occupying the same ecological niches3, and with similar life form and life cycle, may compete for the same resources and roles, with the likely result being one species out-competes the other. In reviewing the available research applicable to Hydrocotyle management in the Canning River region (Swan River Trust, 1996), the option of competitive displacement was not considered as a suitable approach to pursue.

Species with comparable ecological niches to H. ranunculoides include several other Hydrocotyle species, such as H. muriculata; and Centella asiatica (Centella) (Plate 8), both of which belong to the same Family (Apiaceae). Although these two species have remarkably similar growth forms to H. ranunculoides (rhizomes and stoloniferous, vegetative growth, and similar, kidney-shaped leaves), both are largely terrestrial species which can occupy moist habitat but are not able to grow out over open water.

Given this, the use of such species to competitively displace Hydrocotyle is limited only to moist, lower to upper riparian areas along the Canning River or the lagoons, which may frequently become moist or puddled. It is noted that Centella is presently very common in the Hydrocotyle infested region, after being introduced in the Canning River Regional Park areas of interest as part of re-vegetation (Plate 9).

It is unlikely that small-to-medium sized sedges (such as Lepidosperma spp., Schoenoplectus validus, Juncus spp., Bolboschoenus fluviatilis or Carex spp.) can physically displace a stoloniferous creeper like Hydrocotyle. Hydrocotyle stolons can easily creep and grow between sedges in moist habitat, although the physical competition for both space and resources (nutrients, in particular) could be expected to weaken the growth forms.

3 The ‘ecological niche’ involves both the place where an organism lives and the roles that an organism has in its habitat. For example, the ecological niche of Hydrocotyle growing in the infested waterways and adjacent areas can be regarded as absorbing sunlight, water and nutrients (for photosysnthesis), providing shelter and food for various other organisms, and giving off oxygen into the atmosphere.


Plate 8 A close up view of Centella asiatica in upper riparian areas

Plate 9 Extensive Centella stands in Canning River Regional Park

However, robust, large-sized macrophytes, such as Cumbungi (Typha orientalis) and some bulrushes (Eleocharis spp.) would prevent Hydrocotyle from establishment, in most situations, except where there are water channels running through the macrophyte stands (as evident in Wilson Wetland 1 and 2).

After Hydrocotyle has been controlled and eradicated from an area, revegetation with native sedges – either by re-planting, or by seeding – is a viable option, and if these plants establish in dense stands, they could be expected to reduce the chances of Hydrocotyle re-infestation.

4.4.7 Ecological Control – Salinity and Flow manipulations

Previous studies have shown that Hydrocotyle is quite sensitive to salinity levels if plants are exposed for several days. The decline in salinity levels in the Wilson Wetlands on the north-eastern arm; and on the Canning River reaches, upstream of the Kent Street Weir, is probably a critical factor in the establishment and abundance of Hydrocotyle in these areas.

Based on the susceptibility of Hydrocotyle to extended exposure to salinity, an option considered in the long-term strategy (Klemm et al., 1993; Swan River Trust, 1996) was the possibility of manipulation of salinity in the freshwater sections of the Canning River by the removal of the weir boards.

Lowering the boards at the Kent Street Weir allows salt water to penetrate the freshwater sections of the middle and upper Canning River reaches. This method has been successfully used in the past to control Hydrocotyle in the main river channel.

Webster (1994) suggested salinity manipulation was a tool to manage Hydrocotyle in some sections of the river. However, research indicates that Hydrocotyle growing on the river bank, in the lower and upper riparian areas, above the water level, cannot be controlled using this method. Also, two of the key sites infested with Hydrocotyle, (Bannister Creek and Wilson Wetlands) both connect to the Canning River estuary below the Weir.

The following observations can be highlighted from the review of information and consultations:

As noted by the Swan River Trust (1996), the only method of killing Hydrocotyle infestations through salinity manipulation is by treatment with granular salt, or by actively pumping saltwater into the affected areas. However, the expense of installing and maintaining pumping equipment and the need to protect equipment against vandalism and theft were identified as major constraints.


Salinity manipulation has been considered as a long-term solution for managing Hydrocotyle infestations in the Wilson Lagoon, by diverting the freshwater inflows and allowing the area to revert to estuarine marshlands.

Manipulation of salinity levels to control re-infestations of Hydrocotyle in the main river channel is currently limited to spring and summer, when the advancing salt wedge is likely to penetrate past the weir. However, winter rains can create a freshwater layer that may sit above the denser, salt layer, and any Hydrocotyle, floating on the surface may not be affected by the underlying salt wedge. The use of this method may also be restricted, if there are still irrigation licences to withdraw freshwater from the River between Kent Street and Nicholson Road Bridge.

Concern has also been expressed that the removal of the Kent Street Weir, or similar salinity manipulations would result in the gradual replacement of freshwater vegetation by estuarine vegetation. Although the saltmarsh vegetation, associated with the Canning River estuary is highly valued, there is no consensus on whether weir removal is a preferred option of the community. The Weir has been recognised as part of the area’s cultural heritage and the River channel above the weir, as an invaluable recreational resource and freshwater wildlife habitat.

Although largely untested, increasing flow and higher water levels may temporarily restrict the growth of Hydrocotyle in situ, but may increase the spread of the plant downstream. According to Newman et al. (2009), increasing rooting depth to below 1 metre may reduce the ability of Hydrocotyle to root at the margins. This, however, is unlikely to be a feasible option in most infested waterbodies.

Reducing the amount of suitable rooting substrate by piling or preventing access to suitable areas by netting off sections may prove effective. However, in both WA and overseas, there is recognition that the environmental manipulation options are likely to be expensive to implement and are largely untested.

4.4.8 Other Non-Chemical Methods - Use of Heat (Steam or Flame)

Current concerns of potential environmental harm that can be related to widespread overuse of herbicides and high levels of mechanical activities (such as tillage and land-clearing) has led to the development of thermal weeding as an alternative, non-chemical weed control method.

Steam weeding kills weeds by exposing the target plants to very high temperatures in super-heated, saturated steam (between 100 0C and 120 0C). This causes instant blanching and death of non-woody, fleshy plants, in most cases.

The method is promoted as an environmentally-friendly alternative, which does not leave a lasting impact on the soil or the environment. Although the method is mostly suitable for annual and non-woody species, plants with perennial growth habits (underground rhizomes, tubers, corms and bulbs) can also be killed with repeated applications.

Steam weeding is increasingly becoming popular for weed control in municipalities, mostly on hard surfaces, such as curb-side weed control in urban areas, and around sensitive sites (such as public places, schools, playgrounds). The method also has application in larger agricultural situations as well, such as organic farming, orchards, vineyards and row crops (Source: Weedtechnics - http://www.weedtechnics.com/)

There is no literature or research available from Australia or overseas to gauge the effectiveness of steam weeding on patches of Hydrocotyle. However, steam weeding appears to be a technique worth investigation, particularly for sensitive sites such as Bannister Creek or Wilson Wetlands.

http://www.weedtechnics.com/


In the current situation in the Canning River regions, the application of steam weeding may be limited due to the location of the remaining major infestations (i.e. entrenched within Wilson Wetlands and a few other similar lagoons). However, the method deserves investigation, provided the equipment can be deployed effectively close to waterways.

Similar to steam weeding, the effects of a strong oxidising agent - hydrogen peroxide (H2O2) - treatment and flame-torching have been tested on potted plants overseas (van der Burg, 2010; van der Burg and Michielsen, 2010). The authors suggested that in contrast to the former, repeated short burning with a butane torch in early spring or after rigorous removal may be effective to remove stands growing on certain types of embankments. However, field testing of these techniques is needed (Hussner et al., 2012).

4.4.9 Biological Control and Natural Enemies

Klemm et al. (1993) reported that biological control was not considered a practical solution for the control of Hydrocotyle in the Canning River Regional Park because of the time and effort required to research and develop a control agent.

Also, there are 55 species of Genus Hydrocotyle in Australia. The control agent will have to be specific to H. ranunculoides to avoid damage to other Hydrocotyle species, as well as commercial crops, which are of the same family (i.e. Carrot and Celery). Although several Hydrocotyle species are food sources for many insects and animals, McChessney (1994) noted that H. ranunculoides appeared to be unpalatable to some invertebrate herbivores tested.

Overseas research (reviewed by Newman, 2006; EPPO, 2006; Hussner et al., 2012; CABI, 2015) indicates that presently there are no known methods of biological control appropriate for use in the UK and Western Europe.

However, a weevil - Listronotus elongatus (Plate 10) has been demonstrated to feed exclusively on Hydrocotyle ranunculoides in Argentina. The adult weevil feeds on leaves by scraping away the leaf surface and forming discrete holes, some of which become infected by unidentified pathogens. The adult females lay eggs in the base of the petiole and the developing larvae burrow down into the stolon (Hussner et al., 2012).

Plate 10 Weevil – Listronotus elongatus feeding damage on Hydrocotyle

Researchers have observed extensive damage caused by relatively small numbers of the weevil Listronotus elongatus to Hydrocotyle plants in Argentina. Other insects, including Diptera (Flies) larvae and Lepidopteran larvae (Moths) have also been observed to feed well on Hydrocotyle.

In the Netherlands, Belgium, Germany and the UK, research appears to be underway on developing the biological control option by weevils (especially Listronotus elongatus Hustach) and other potential natural enemies (see references in Newman et al., 2009; Newman and Duenas, 2010). Biological control research has also considered the possibility of using pathogenic organisms that have been identified as affecting Hydrocotyle (Newman 2006).


Given the success of biological control agents in aquatic weed management4 as suggested by Klemm et al. (1993), this option may need to be re-considered as a viable future option – if complete eradication of Hydrocotyle is not achievable by other means. Until biological control options are further studied, there is consensus that management of the species should rely on integration of other methods.

4.5 Chemical Control – Herbicides

As documented by various reports (Klemm et al., 1993; Swan River Trust, 1996; Webster, 1994; 1995; Ruiz-Avila and Klemm, 1996), since the early 1990s, herbicides have been investigated as a tool to control Hydrocotyle infestations in the Canning River regions (see Section 2.3).

Ruiz-Avila and Klemm (1996) reported on the two-step management of Hydrocotyle, which was implemented in the Canning River regions in the mid-1990s. This involved physical (manual or mechanical) removal of most plants, followed by treatment with Round-up® Glyphosate at an application rate of 360 g ha

-1.

Recommendations in WA

The Department of Agriculture and Food WA (Government of WA, 2015) has indicated that the information on Hydrocotyle control (https://www.agric.wa.gov.au/declared-plants/declared-plant-control-table) may be out-dated. However, the Control Table on the Website is useful to understand the herbicides that were considered effective and previous recommendations.

Table 4 Herbicides recommended for controlling Hydrocotyle ranunculoides*

Group Herbicide Notes on Applications

Contact Herbicides

Diquat, 200 g/L a. i.

1:100 dilution; 10 L/ha; for spot spraying; wetting agent dilution 1:400; any time when green leaf surfaces are exposed;

Not very effective on large areas because regrowth occurs. Higher rates of 50 L/ha to a water depth of 1 m may work, but may be expensive

Systemic Herbicides

Glyphosate, 360 g/L

1: 100 dilution; 10 L/ha; apply during summer to winter; Wetting agent dilution 1:1000 - Using a non-ionic surfactant, such as BS-1000

* Source: Department of Agriculture and Food, Government of WA (2015)

The same control recommendation states that Tordon 2G5 has also been shown to be very effective on Hydrocotyle growing close to the banks of water courses. Metsulfuron-methyl and Chlorsulfuron have also been mentioned as very active on Hydrocotyle.

West Australian studies have shown that spraying the contact herbicide - Diquat on the leaf surface of Hydrocotyle mats reduced the weed cover by 80 – 90%, but the effectiveness decreased rapidly, and considerable recovery was observed on all treatments after 30 days.

4 Well-known Australian examples include: Salvinia (Salvinia molesta) control with the Salvinia Weevil - Cyrtobagous salviniae; Water Hyacinth (Eichhornia crassipes), control with Water Hyacinth Weevil - Neochetina eichhorniae; Alligatorweed (Alternanthera philoxeroides) control with the Flea Beetle – Agasicles hygrophila. 5 Tordon 2G Herbicide is a mixture of Picloram and Aminopyralid; it is recommended for the control of many difficult-to-kill perennial weeds, such as ragwort, thistles, oxeye daisy and giant buttercup, as well as broom, gorse, tutsan, sweet briar and blackberry in Australia.

https://www.agric.wa.gov.au/declared-plants/declared-plant-control-table



This study recommended the use of a systemic herbicide in preference to Diquat, as only the exposed portions of the plant were killed and the resulting regeneration necessitated repeated treatments (Pierce and Raynor, 1992).

Glyphosate

In WA, historically, the integrated control methods have been physical removal (by manual or mechanical means), followed by herbicide treatments. The herbicide most widely used for Hydrocotyle control in the past has been the Round-up® formulation of Glyphosate.

The original Round-up® formulation, developed for terrestrial, agricultural applications, contains a popular surfactant – polyethoxylated tallow amine (POEA)6. This surfactant was found to be significantly more toxic to fish, amphibians and aquatic invertebrates than the herbicide itself (Bidwell and Gorrie 1995; Klemm et al., 1993; PMEP 1999).

More recent formulations developed in the mid- to late-1990s, such as Roundup Bi-active®, contain a substantially less toxic surfactant and are specifically designed for use in aquatic habitat. In WA and other Australian States, Roundup Bi-active® has been the recommended option for use in waterways for control of problematic emergent weeds since this time (Mann, 1998).

Metsulfuron-methyl

In recent years, Metsulfuron-methyl has been the herbicide of choice for Hydrocotyle control, because research in WA established that it was highly effective against Hydrocotyle.

Metsulfuron-methyl is a selective herbicide used on broad leaf weeds and some grasses, and can kill native species. It is a systemic herbicide, which is broken down in to harmless by-products (PMEP, 1999). It is excreted from the body within hours and has a low toxicity to fish, a low toxicity to mammals and birds and a very low toxicity to aquatic microorganisms and terrestrial invertebrates (Klemm et al., 1993; Moore and Fletcher, undated; PMEP 1999).

This herbicide has a half-life of 1 – 4 weeks in soil and 0 – 1 week in water (Klemm et al. 1993). However, Moore and Fletcher (undated) reported residual activity of up to 2 years where it had been applied directly to the soil.

In 2007, the WA Department of Health issued Public Service Circular No. 88 (PSC 88) Use of Herbicides in Water Catchment Areas to protect Western Australian drinking water resources from unnecessary exposure to herbicides. The Circular is a ‘best practice’ policy statement that applies to all government departments and their contractors and provides advice on the use of herbicides in drinking water catchment areas including approved chemicals, application methods, safe storage and disposal. There are seven herbicides listed as permissible in water catchment areas, with the use of Metsulfuron-methyl restricted to hand-held/spot sprays to control weeds such as Blackberry and Cape Tulip.

The Circular states as follows: “…the specified herbicides may be used against declared plants and other undesired weeds on water catchments and water channels or in the vicinity of reservoirs provided timings, techniques and precautions ensure there is no spray drift or early run off from treated areas likely to contaminate reservoirs, rivers or streams. All applications must be under the supervision of a person experienced in the use of herbicides...”

6 Polyethoxylated tallow amine (POEA) is a non-ionic surfactant used in many glyphosate formulations, a widely applied herbicide both in agricultural and urban environments. POEA has been shown to be toxic to various aquatic organisms. Characterization of technical mixtures using ultra-high performance liquid chromatography (UHPLC) and mass spectrometry shows POEA is a complex combination of homologs of different aliphatic moieties and ranges of ethoxylate units.


Available literature (Pierce and Raynor, 1992) and discussions with stakeholders indicate that a range of Metsulfuron rates are highly effective on achieving Hydrocotyle control. While the standard rate of Metsulfuron (10 g per 100 L of water) provides a complete kill, even a quarter rate (i.e. 2.5 g per 100 L of water) has been found to be highly effective on Hydrocotyle (Matt Grimbly, SERCUL, July 2015, personal communications).

The quarter rate has been favoured in recent years (see Section 2.4) as the main treatment of choice, because of reduced herbicide load in the environment. Also, despite Metsulfuron’s selectivity, the local experience is that a quarter rate is less phytotoxic to sedges and other aquatic species that might be susceptible. It is also recognised that any reduction in activity by the use of a quarter rate will be compensated by more frequent applications, which are part of regular monitoring and inspections in the treated areas.

It should be noted that Metsulfuron-methyl, although not registered for use in aquatic situations in Australia, has been granted ‘Off-label’ use against major aquatic weeds, such as Alligatorweed in NSW. Based on the local research, in WA, Metsulfuron use is covered by the APVMA Permit 1333, issued to the WA Department of Agriculture and Food. The permit states that the product Metsulfuron can be used in non-crop areas for environmental weed control, up to the maximum label rate (i.e. standard rate: 10 g/100 L).

Herbicides Used Overseas

In the UK, Newman and Dawson (1999) described the effects of Glyphosate (2.16 kg ha-1

) and 2,4-D amine (4.23 kg ha

-1 ) on Hydrocotyle in field experiments. In one study, they reported that

Hydrocotyle was more susceptible to the phenoxy-acid herbicide 2,4-D Amine and was recalcitrant to Glyphosate treatments. The application of 2,4-D amine, at intervals of 3 weeks, delayed regrowth of the plant by up to 12 weeks and was found to be the optimum for chemical control (Newman and Dawson, 1999). However, 2,4-D Amine was not well-translocated in the plant and unaffected parts tended to overgrow the treated biomass, reducing efficacy. Low volume applications of Glyphosate have also been used to limit regrowth, although Newman and Dawson (1999) suggested that further development of the technique is required.

The Centre for Aquatic Plant Management in the U.K. recommends chemical treatment with Glyphosate followed by spot treatment or mechanical removal (Newman, 2006). However they note that complete eradication may not be possible.

In the USA, herbicide recommendations for Hydrocotyle control have been given in the Handbook on Weed Control in Natural Areas in the Western United States (DiTomaso et al., 2013). The recommendations do not include Glyphosate, probably because it is non-selective, and may cause unacceptable non-target effects on other vegetation in natural areas. Instead, the herbicides recommended for managing Hydrocotyle in natural areas include only those which are selective and have some systemic activity (i.e. 2,4-D Amine, Triclopyr, Bispyribac-Sodium, Imazamox, Imazapyr, and the contact herbicide –Diquat).

4.6 Integrated Control

As reviewed by various authors (Klemm et al., 1993; Swan River Trust, 1996; Webster, 1994; 1995; Ruiz-Avila and Klemm, 1996), the research and management experiences documented in the available literature have clearly highlighted the importance of integrated control in managing Hydrocotyle in the Canning River.


In WA, historically, the methods integrated have been physical removal (by manual or mechanical means), followed by herbicide treatments. In the past, the herbicide most widely associated with Hydrocotyle control was the Round-up™ formulation of Glyphosate, which has since been replaced by the aquatic registered Bi-active® Glyphosate.

In recent years, Metsulfuron-methyl has been the herbicide of choice, applied at a quarter rate (2.5 g per 100 L of water), integrated with manual removal.

Best practice

Overseas research, particularly in the UK and Western European countries (The Netherlands, Belgium and others), has established that while there are several methods that may be used to control Hydrocotyle, none of them give a complete solution. Methods that have been favourably considered for integration with manual and mechanical removal are herbicides.

Research in the UK and Western Europe has led to the establishment of a ‘best practice’ for effective long-term control of Hydrocotyle (Newman, 2006; Newman et al., 2009; Newman and Duenas, 2010; Hussner et al., 2012).

Elements of the program are as follows:

Remove Hydrocotyle plants/colonies as soon as they are observed by manual hand-picking.

In major infestations, include a thorough control program of mechanical removal of as much biomass as possible, followed by intensive hand-picking.

Where physical or mechanical cutting techniques are used, the affected areas are to be fenced off to prevent the downstream spread of plant fragments.

All cut foliage should be removed from the water body.

Follow-up treatments with herbicides may be required to ensure a high degree of control, although eradication may not be achieved in areas where it has formed extensive stands.

The ‘best practice’ recommendations acknowledge that physical control methods are likely to have little effect other than a short-term reduction in the local extent of Hydrocotyle infestations. It is also accepted that Hydrocotyle infestations in some situations are very difficult to completely control, and may prove impossible to eradicate from some locations.


5. Hydrocotyle Weed Management Plan Based on the knowledge of the ecology and biology of Hydrocotyle and management experiences summarised in Section 2 and Appendix B, and discussions of key issues and principles stated in Section 3, this Section outlines the Hydrocotyle WMP. Notes and relevant discussions are provided with justifications for the proposed actions and implementation plan.

Elements of the Hydrocotyle WMP are briefly, as follows:

Justification for Management Action;

Aims and Objectives;

Legislative Control;

Stakeholder engagement;

Site-specific management and prioritisation of sites for management;

Preventative weed management;

Management of new infestations and existing weed infestations;

Creating awareness and providing education and training;

Implementing the Action Plan with co-ordination of activities across jurisdiction; and

Monitoring, evaluation, reporting and improvement (MERI Framework).

5.1 Justification for Management Plan

The Triple Bottom Line impacts of Hydrocotyle infestations given in Table 2 provide the justification for management action. Briefly, the major considerations are as follows:

• Hydrocotyle has been known to infest the freshwater sections of the Canning River’s shorelines and its associated Lagoons and Wetlands, as well as tributaries, including the drainage channel network. The impacts of the weed are well-established and include alteration of ecosystem processes, such as sedimentation, nutrient cycling and other ecosystem processes.

• The historical Hydrocotyle infestations were vast, and often reached levels that interfered with recreational activities and other water uses.

• When established, the extensive Hydrocotyle stands tend to dominate the local environment, and it is highly likely that such infestations alter local waterway habitat conditions. This could displace native aquatic plants or riparian species by preventing their recruitment, establishment or regeneration. As a result, Hydrocotyle may reduce, modify or eliminate resources (e.g. food, cover, refuges) used by native animals.

• Heavy infestations may also cause flooding by impeding the flow of water, alter succession and hinder the restoration of natural communities.

5.2 Overall Aim of WMP

The aim of the Hydrocotyle WMP is effective and integrated management of Hydrocotyle in the Canning River region through collaborative effort, resulting in reduced infestations, eradication where possible, and prevention of further spread of the weed, thus protecting natural ecosystems and maintaining land and water quality.


5.3 Objectives of the WMP

1. To have a collaborative framework in place that allows all stakeholders to work together to manage Hydrocotyle infestations and new outbreaks in the Canning River region, including Lagoons and Wetlands;

2. To eradicate smaller infestations and achieve an overall reduction in the extent and intensity of current, larger infestations, using an integrated weed management approach;

3. To effectively prevent further spread of Hydrocotyle beyond current boundaries;

4. To involve all stakeholders in cooperative efforts against Hydrocotyle on both public and private lands. This includes implementation of effective education and awareness programs;

5. To have any new technologies and improvements in management options, advised through research and development, supported and promoted in the overall management of Hydrocotyle in the Canning River region.

6. To actively seek funds to support on-going monitoring and management of Hydrocotyle by stakeholders and to have these efforts supported by State and Federal Governments and other Stakeholders.

5.4 Legislative Control and Prevention

At the Western Australia State level, the Department of Agriculture and Food (DAFWA) sets the priorities for declared pests under the Biosecurity and Agriculture Management Act 2007 (BAM Act) through the Minister for Agriculture. All species that were declared under the Agriculture and Related Resources Protection Act 1976 have been transitioned to have equivalent declarations under the BAM Act.

Regulation 7 of the BAM Act allows for the establishment of categories of declared pests for both animals and plants (Table 5).

The legal status of Hydrocotyle ranunculoides is that it is a declared environmental weed in Western Australia (https://www.agric.wa.gov.au/organisms/126997) and is listed as a C3 species under the BAM Act.

Table 5 Declared Plant Classes in WA and Actions required by Law

Declared Plant Class

Action required by law

C1 - Exclusion If in the opinion of the Minister introduction of the declared pest into an area or part of an area for which it is declared should be prevented [Note this allows for regulation of movement within the State.]

C2 - Eradication If in the opinion of the Minister eradication of the declared pest from an area or part of an area for which it is declared is feasible;

C3 - Management If in the opinion of the Minister eradication of the declared pest from an area or part of an area for which it is declared is not feasible but that it is necessary to —

(i) alleviate the harmful impact of the declared pest in the area; or

(ii) reduce the number or distribution of the declared pest in the area; or

(iii) prevent or contain the spread of the declared pest in the area.

https://www.agric.wa.gov.au/organisms/126997


The DAFWA Invasive Species Strategy approach involves direct actions for ‘Prevention’ and ‘Eradication’, and for capacity building to undertake actions within industries and community for ‘Containment’ and ‘Asset-based Protection’.

In South Australia, Hydrocotyle is declared under Class 1a, a classification for prohibited aquatic plants. Its presence must be notified and the plant must be destroyed (throughout the entire state).

Given that Hydrocotyle is already a ‘declared pest plant’ in WA, this aspect has been partly dealt with. However, further categorization into a plant of the ‘highest priority’ within the declared plant category would assist future management and resource allocations.

A prevention strategy for Hydrocotyle includes public relations activities, awareness campaigns and possibly by-laws, which prevent the introduction of the species into other regions, or its import to WA from other regions in Australia in the future. Prevention must include engagement with the aquarium industry (probable source of entry), creating lists of species prohibited (based on risk assessments), as well as monitoring and inspections of potential sites where Hydrocotyle could occur.

5.5 Stakeholders

Relevant details of the Stakeholder engagement process and outcomes of consultations are provided in Appendix A and B. A summary is provided below:

5.5.1 Stakeholders and engagement process

The following is the list of primary stakeholders involved in developing the Hydrocotyle WMP:

Perth Region NRM;

Swan River Trust (now part of WA Department of Parks and Wildlife, DPaW);

WA Department of Parks and Wildlife, DPaW;

WA Department of Agriculture and Food;

Local Government - City of Canning and City of South Perth;

South-East Regional Centre for Urban Landcare (SERCUL);

Wilson Wetlands Action Group (WWAG) and Canning River Regional Park Volunteers;

Weed Control Operators - Martins Environmental Services, and Bunyip Contracting.

Engagement activities and the consultation process included the following:

The engagement methodology involved a number of key activities initially to identify stakeholders, inform them about the Project process, provide opportunities for comment and document feedback for consideration by the Hydrocotyle Working Group.

A Stakeholder Alignment Workshop was held on 14th July 2015 to align stakeholder understanding, objectives and expectations. This process established a vision, weed management goals, conservation values and goals and performance measures. The discussions led to a common understanding and a coherent vision for the study area.

A formative evaluation was conducted in the form of in-depth, one-on-one discussions and interviews with key stakeholders regarding opinions, past experiences, issues and concerns regarding weed control - to inform the Hydrocotyle WMP. The discussions expanded on information provided in the Stakeholder Alignment Workshop.

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/glossary.htm%23aquatic


Upon the completion of the technical review, a Stakeholder Consultation Workshop was conducted on 18 August 2015 with the aim of widening the engagement process and discussions on matters related to Hydrocotyle management in the region. The facilitated Workshop provided an opportunity to discuss mapping, current levels of infestations, factors that would assist prioritisation of management zones and available management options. It also allowed all stakeholders to put forward their points of view in open discussion and develop a better understanding of institutional interests, constraints and issues of concern that needed to be addressed by the WMP.

Consultation also solicited opinions on monitoring and review of the Hydrocotyle WMP.

5.5.2 Stakeholder visions and goals

In developing the Hydrocotyle WMP, the following key visions were shared by all stakeholders:

Eradication of Hydrocotyle from the Canning River region; and

The continuation of positive and enduring stakeholder collaboration in managing Hydrocotyle in the Canning River region.

Additional goals for the WMP, established by the stakeholders include the following:

Emphasise the investigation and application of non-herbicide control methods;

Empower the community to continue to deliver benefits for the Canning River environment;

Increase community awareness and education of aquatic weed problems;

Retain community enjoyment of the river environment;

Ensure the WMP is a benchmark for aquatic weed management.

5.6 Mapping of Infestations

The current infestation levels are depicted in the Map given in Figure 6. The survey indicated that in most areas, Hydrocotyle infestations are at low to very low levels, except in sections of Wilson Wetlands. This result is encouraging, and shows the success of implementing and continuing the management program.

The following observations can be highlighted:

Bannister Creek – the survey indicated a few colonies of Hydrocotyle along the creek; this result is in general agreement with SERCUL Mapping (see Figure 4);

Mill Street Drain – no Hydrocotyle was found, which matches the results reported by SERCUL (see Section 2.4.2);

Main River channel and shorelines up to about 2 m above river bank – only minor colonies were located at a few places; this result also matches the levels of control reported by the Swan River Trust (See Section 2.4.3);

As shown in Figure 4 and Figure 6, the main areas of infestations were in the Wilson Wetlands on the northern side; and two other wetlands on the southern side (adjacent to Marmot Way and Colahan Way);

Although a control program is being implemented, some of the infestations in the Wilson Wetlands were heavy; Appendix D provides an overview of these infestations.

ALBANY HIGHWAY

LEACH HIGHWAY


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Figure 6


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G:\23\15602\GIS\Maps\MXD\2315602_Z011_HydrocotyleExtent_2015_A4_Fig6.mxd


0 50 100 150 20025

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LEGEND


Date 03 Sep 2015

Perth Region NRMHydrootyle Management Plan

Extent of Hydrocotyle infestations in the Canning River region Lagoons, Wetlandsand Tributaries (July 2015)

Data source: ESRI/World Imagery. Created by:atdickson

180 Lonsdale Street Melbourne VIC 3000 Australia T 61 3 8687 8000 F 61 3 8687 8111 E [email protected] W www.ghd.com

Paper Size A4

DRAFT

Major Hydrocotyle InfestationLow Density Hydrocotyle

!( Minor Hydrocotyle Infestation

Principal RoadMinor Road


5.7 ‘Site-Specific Management and Management Zones

The information review indicates that the known infestations of Hydrocotyle in the Canning River and associated tributaries, lagoons, wetlands and in the drainage network have been managed as five management zones. They are:

Management Zone 1 – Wilson Wetlands and Lagoon areas within the Canning River Regional Park and adjacent land owned by Christian Brothers (see Appendix D);

Management Zone 2 – Canning River Main Channel from Kent Street Weir to Nicholson Bridge and the river bank areas in the Canning River Regional Park; managed by the Swan River Trust (now part of DPaW)

Management Zone 3 – Water Corporation Infrastructure – Welshpool Basin and Mill Street Drain;

Management Zone 4 – Bannister Creek; managed by The City of Canning;

Management Zone 5 - Collier Pines Drain at Bodkin Park, Waterford; Managed by City of South Perth and Water Corporation.

Management Zones 2, 3, 4 and 5 are based on the ‘asset owner’ model, where the agency has the primary control responsibility. Management Zone 1 – Wilson Wetlands is being managed by a collaborative arrangement and partnership between the Wilson Wetlands Action Group (WWAG), Christian Brothers, Department of Parks and Wildlife (DPaW) and City of Canning.

Given the low level of infestations in Management Zones 2, 3 and 4, further categorisation of these areas into smaller management units is considered not necessary, except for the three areas of wetlands and lagoons, located on the southern side of the River.

These three Wetland areas are proposed as Management Zone 2b, because they are an integral part of the Canning River, in that reach (see Map) and Hydrocotyle infestation levels are considerably lower than in Wilson Wetlands.

As discussed in Section 3.6.4, the prioritisation of areas for Hydrocotyle control considered: (a) Potential for further spread within or beyond an infested area; (b) Consequences and the impact of on-going infestation; and (c) Management feasibility within a given management area. Other factors (such as conservation values of those areas) can also be considered, but do not appear to make much of a difference to the results of ranking, shown in Table 6.

Accordingly, all areas where control action taken thus far has been successful receive the highest priority ranking, so that eradication can be attempted.

The Wilson Wetlands (Zone 1) and the Lagoons on the southern side (Zone 2b) have difficult-to-access infestations, which require different combinations of approaches and significantly more effort, time and resources for management. The priority rankings for the Wilson Wetlands and the Southern Lagoons are therefore ‘medium’. These aspects are further discussed below.

5.8 Specific Management actions

5.8.1 Influential Factors

Specific management actions for the different sites and management units are largely based on the past and present management experiences in the Canning River regions, as well as overseas experiences of what works and what does not. Each combination of options that can be integrated is determined principally by the goal of effectiveness of the methods to significantly reduce the abundance of Hydrocotyle; or eradicate it from infested areas.


Table 6 Management Units - Prioritisation for Control with rationale*

Management Unit PFS CFI MF Ranking Score

Rationale for Scoring

Zone 1 - Wilson Wetlands and Lagoon areas

5 3 2 (5 + 3) x 2 = 16

Medium priority; management is not immediately feasible; Hydrocotyle is already widely established; potential for further spread is very high; however, it is contained within the Wetlands; control may be achievable at a future date

Zone 2a – Canning River Main Channel and shorelines

2 4 3 (2 + 4) x 3 = 18

Highest priority; management is feasible; consequences of further impacts are also low; eradication is also achievable

Zone 2b – Canning River Wetlands and Lagoons on the southern side

4 4 2 (4 + 4) x 2 = 16

Medium priority; management is not immediately feasible; Hydrocotyle is already established, but low-levels; potential for further spread is high; however, it is contained within the Wetlands; control may be achievable at a future date

Zone 3 – Drainage Infrastructure

2 4 3 (2 + 4) x 3 = 18


Zone 4 – Bannister Creek

2 4 3 (2 + 4) x 3 = 18


Zone 5 - Collier Pines Drain at Bodkin Park, Waterford.

2 4 3 (2 + 4) x 3 = 18


* Details of scoring used for prioritisation are given in Section 3.6.4

The management options are also greatly influenced by the duration of control offered by a method, costs of implementation, advantages and drawbacks, including potential environmental impacts and safety of operational staff. In other words, management techniques need to be considered from the viewpoints of logistical, environmental, economic and legal factors.

As discussed in Section 4.3.2, an important step is to determine how much control over what period of time would be needed to achieve the desired outcome. For instance, where should a low-level of control be applied for a longer period, safeguarding environmental concerns or conservation value of a site? And, under what circumstances would a high-level of control be necessary? Which combination of techniques would allow a high level of control?

In devising the specific recommendations for Hydrocotyle management in the different management zones, important influential factors were considered. These factors were highlighted by stakeholders during the consultation process (Section 5.5.2 and Appendices A and B) and have also been identified in historical reports. These are discussed below:

Type and extent of the plant’s growth: The extent of existing Hydrocotyle infestations is an important factor; if the infested areas are small, then large-scale methods would be inappropriate; in contrast, large infestations would require effective interventions to prevent those from becoming sources of further spread.

Timing of treatments: Hydrocotyle grows mostly in spring and then expands over summer; its growth is likely to be more susceptible to treatments in spring and early summer (i.e. September to December).


Probable duration of control: Experience shows that both short-term control (methods that would provide control for a few months to a growing season) and long-term control (1 to 2 years; or 3 to 5 years) will help reach the overall objectives of controlling Hydrocotyle and moving towards its eradication in the region.

Site-specific constraints: Sites, such as the Wilson Wetlands and Lagoons and the Wetlands on the southern side of the Canning River are with poor water quality, slushy mud, depressions and submerged tree roots and logs and other debris. These would hamper access by staff, and also limit the application or movement of machine or equipment to control infestations.

Some sections also have large extents of Typha growth, preventing access for inspections and control. Although water quality is generally poor as a result of nutrient enrichment, the well-recognised conservation values (refuges for native flora and fauna and ecological processes) of the Wetlands are a major constraint to deploying techniques that may do more harm than good (discussed below).

Conservation status and ecology of the waterway or waterbody: The presence of particularly sensitive flora or fauna in a given area would limit the use of some control methods because they may disturb the ecology of the system. However, the adverse effects are largely determined by the scale of the operation, and not necessarily by the method.

Balancing potential impacts with beneficial effects and environmental protection: Any control method will have some negative impacts on the local environment, at least in the short-term. However, it is necessary to weight the potential benefits of control achievable by a method against the harm that could occur by not using the method for controlling a pest species effectively.

Effective low-impact techniques: Preference is for methods that have the least impact on sensitive areas, provided the methods are likely to succeed. Manual control, either by hand-picking, or assisted by rakes and small implements, has the least impact. Manual control is feasible in many areas to remove loosely-attached colonies, or larger mats. Manual control needs to be combined with methods to capture fragments that may float in water, and also be repeated at a high frequency.

Other techniques include the use of shading, laying of weed mats over an infestation to reduce its vigour, which is applicable in lower to upper riparian zones in some shoreline areas. Steam weeding is also not precluded, although the method has not been tested for Hydrocotyle control. However, its use may be limited to control areas where the equipment can be effectively deployed.

Mitigation of control impacts: Wherever possible, control action should be followed by impact mitigation. An example of impact mitigation is to undertake re-planting and re-vegetation of areas that have been subjected to a control program, such as emergent riparian vegetation along the Canning River main channel shorelines. There is already rich riparian vegetation with high species diversity in some sections on either side of the Canning River channel. However, a well-targeted re-vegetation plan, including the use of existing seed and propagule material, should be implemented. The benefits include opportunities to: control other non-native species in the riparian zones; further increase native plant species diversity on the shorelines; and opportunistically monitor any future growth of Hydrocotyle in previously infested areas.


Program Costs: If specialized equipment is needed for control, these would add considerable costs of hire and operations. They can only be justified on the grounds of overall effectiveness, safety and other benefits (i.e. saving time and effort). The hiring of an amphibious craft (such as a Truxor) appears to be warranted to cut swathes through Typha infestations and access the Hydrocotyle, which is otherwise difficult-to-access. The use of an amphibious machine also allows access to shorelines from the water.

Human health and safety concerns: Most of the time control activities can be undertaken without affecting recreational uses or other uses of water by the public. Despite this, control activities in difficult terrain pose safety risks to staff and operators.

5.8.2 Use of Herbicides

As discussed in Section 4.5, herbicides are important tools in the effective management of Hydrocotyle. The use of herbicides in the program has been fully endorsed by the WA Department of Agriculture and Food. However, a history of undesirable impacts from the overuse of herbicides (i.e. extensive use of Round-up™ Glyphosate in the period up to 1994) is well-established in the Canning River region. The negative public perception created in the mid-1990s has lingered on (as evident in Stakeholders’ views).

The discontinuation of the use of Round-up™ Glyphosate formulation and its replacement with the aquatic registered Bi-active® Glyphosate since 1995-96 is regarded as a positive advance. However, Glyphosate’s non-selective mode of action is a limitation for its use in riparian zones.

There is however, well-established evidence that Hydrocotyle infestations are quite susceptible to a standard spot treatment with Bi-active® Glyphosate, and the local experience is that a few repeat applications will eradicate populations and even dense mats. The relatively benign environmental profile of Bi-active® Glyphosate and its known high efficacy makes it suitable for managing some of the heavy infestations in the Wetlands and Lagoons, where selectivity is not required; i.e. large mats, loosely floating on water, or interspersed through dense Typha stands.

Metsulfuron-methyl, as discussed in Section 4.5, has been the herbicide of choice in managing Hydrocotyle in the Canning River region in recent times because of the selectivity it offers and the plant’s susceptibility to the chemical. Although not registered for aquatic use, Metsulfuron use has been approved in an “off-label” permit application to control a specific weed problem.

To reduce herbicide loads being used, SERCUL’s preference has been to use the minimal effective rate of Metsulfuron (i.e. 2.5 g per 100 L), instead of the standard rate (10 g per 100 L of water), and more frequent applications to compensate for any reduction in efficacy. Although the quarter rate has provided a high degree of kill of some infestations (in open situations like the Mill Street Drain), this effectiveness may not be universal across different situations. There is a high possibility of some treatments not being as effective as they could be, particularly on dense mats of Hydrocotyle. Plant uptake and translocation of systemic herbicides are often dose-dependent, and are also highly influenced by the foliar application formulation. A higher rate of Metsulfuron (i.e. 10 g/100 L of water) is more likely to guarantee a complete kill, which a quarter rate may not achieve. Concern has also been expressed by some stakeholders that quarter rate treatments may lead to resistance development, because it may not kill the whole population targeted. More frequent applications also mean increased labour and related costs.

As a result of the review of information, and taking into account local experiences and views of the stakeholders, where selectivity is required, Metsulfuron-methyl may be used at a quarter rate with more frequent applications; or at the standard rate, with less frequent applications (i.e. 3-4 times per year only). In most areas, Metsulfuron use is recommended only as ‘spot treatments’ from a back-pack. In many Hydrocotyle management areas, where control has already been high, frequent Metsulfuron treatments are not considered necessary.


5.8.3 Integration of concordant control methods

Specific recommendations for Hydrocotyle management are provided in Table 7. These are based on the integration of effective and compatible methods, which can be applied to varying degrees to manage Hydrocotyle in the Canning River regions:

Remove Hydrocotyle plants as soon as it is observed by manual hand-picking; Conduct frequent manual removal in all areas as part of regular inspections;

In major infestations, use mechanical removal as a method to reduce as much biomass as possible, followed up by intensive hand-picking. This is applicable in the Wetlands and Lagoons to drastically reduce existing infestations;

Remove all cut foliage or hand-picked materials from the water body for safe disposal;

Where physical or mechanical removal techniques are used, fence off downstream areas to prevent any downstream spread of plant fragments –if this risk exists.

Use low-impact methods, such as weed matting to cover small infestations and reduce their vigour prior to hand-removal. This is possible to varying degrees in all affected areas, particularly shoreline riparian zones;

When the opportunity presents itself, lower the boards at the Kent Street Weir to allow the salinity wedge to push upstream in the main River channel; this would be appropriate particularly when the salinity in the freshwater section is below about 20% of sea water (i.e. Conductivity of about 11,000 µS/cm). The salinity manipulation may assist in creating conditions which are unfavourable for establishment of Hydrocotyle in the River channel. However, this may not assist in reducing the infestations in lower to upper riparian areas.

Follow-up treatments with herbicides may be required to ensure a high degree of control, although eradication may not be immediately achieved in areas with extensive stands.

However, it is important to acknowledge that physical control methods may be limited to achieving a short-term reduction only in the local extent of Hydrocotyle infestations. Whilst excessive herbicide use is not favoured, diligent use is regarded as an essential tool in managing deeply-entrenched Hydrocotyle infestations. It should also be accepted that Hydrocotyle infestations in some situations are very difficult to completely control and may prove impossible to eradicate from some locations.

5.8.4 Conservation Areas – Wetlands and Lagoons

The Wilson Wetlands and other Wetlands and Lagoons are valuable environmental assets and they present particular problems. Hydrocotyle management in these conservation areas should be based on a high-intensity manual removal program, assisted by mechanical removal and, where appropriate, some spot treatments of herbicides.

The time frame for achieving a drastic reduction as a management goal in such areas should be much longer (probably 2-3 years) than for other affected areas. Whilst research trials continue on understanding what factors can be manipulated, including salinity, the focus should be to drastically reduce infestations, starting from the most upstream and gradually heading downstream. The control of infestations should incrementally increase over Years 1, 2 and 3.

There is potential for integrating re-vegetation and re-creating the diversity of macrophyte vegetation that would have previously existed (i.e. brackish water lagoon vegetation) as an integral part of managing Hydrocotyle. The eventual goal should still be to eradicate Hydrocotyle from the Wetlands within a 3-5 year time frame.


Table 7 Specific Management Actions recommended for Management Units

Management Unit Priority Recommended Management Methods

Zone 1 - Wilson Wetlands and Lagoon areas

Medium • Management of Hydrocotyle in the Wilson Wetlands and Lagoons is difficult, largely because of access limitations. Most infestations are in slushy mud, on sediments that have accumulated around the bases of Melaleuca trees, and extend out. Safety to operators must be a paramount consideration in accessing these for control.

• Except in some sections (open water, among Typha patches, and in some trial plots), Hydrocotyle populations within the Wetlands are mostly medium-level infestations, probably due to the shade of the trees. There is potential for further downstream spread from these locations in heavy wet weather; however, current patches are contained within the Wetlands. Also, the saline conditions downstream are unfavourable to the weed’s growth (No Hydrocotyle has been found in Wilson 3 Wetland, which is brackish).

• High intensity manual removal should be undertaken by suitably trained staff, possibly using small boats or kayaks to reduce the larger biomasses entrenched around the bases of trees. Where circumstances dictate (i.e. difficulty to access; safety to staff), chemical treatment may precede manual removal. The current levels of infestations indicate that several rounds of manual removal, conducted fortnightly, or on a weekly basis, prior to the growing season, may reduce infestations to a large extent. This may require additional paid staff to support the efforts of volunteers.

• Some reduction of Typha stands is necessary to access Hydrocotyle in some riparian areas which are otherwise inaccessible. This is particularly the case in accessing infestations from the northern side (Fern Road). It is recommended that the use of a small machine (Truxor) be used to create access by cutting access tracks through Typha patches in boggy areas. The Truxor could also be used to access areas that are otherwise inaccessible, as inspections can occur from both water and land. Where access may be achieved by brush-cutters and/or chainsaws, these tools may be used as required.

• There is potential for integrating re-vegetation and re-creating the diversity of macrophyte vegetation that would have previously existed (i.e. brackish water lagoon vegetation) as an integral part of managing Hydrocotyle. Active re-planting is recommended in areas cleared of Hydrocotyle with species that are known to be thriving within the lagoons. Local eradication should be achieved prior to any revegetation.

• All non-chemical methods, such as shading with weed matting or netting to capture any fragments, are valid techniques within the Wilson Wetlands, while manual removal is intensified, and is combined with mechanical removal.

• If herbicide treatments are to be used – Bi-active® Glyphosate is recommended for wetland areas where there is no risk of damaging native plants. Glyphosate should not be used in areas where various small-to-medium sized native sedges occur. However, excessive Typha stands through which Hydrocotyle has spread could be reduced opportunistically using Glyphosate.


Table 7 (cont.) Specific Management Actions recommended for Management Units


• If selectivity is required in some areas, Metsulfuron could be used, but this should not be the preference. If Metsulfuron is used on a limited scale (depending on size of infestations, which cannot be otherwise reduced), treatments recommended are either the standard rate with an application rate of 3-4 times per 12-month period, or the quarter rate with more frequent applications, depending on permit conditions, or other relevant factors. Application should be spot-spray of small volumes only, applied either from a boat, or from back-back; treat in spring and summer when Hydrocotyle plants are actually growing; adhere to all precautions and guidelines of herbicide use in aquatic environments (in or around water).

• Manipulations of salinity should be examined, but this may not be achievable in the near future.

• Water quality monitoring at the 11 locations established will assist in establishing the interaction of saline seepage and freshwater inflows; these could continue for a period of time (say, next 12 months), so that valuable data would be collected to better understand the changes occurring in the Wetlands.

• The current trials and investigations of the interaction of multiple factors that may contribute to the continuing presence of Hydrocotyle are supported. However, it is proposed that areas of investigation are cordoned off with fencing (as has been done) to prevent any breakouts. Monitoring at downstream sites along the water flow pathways will be required to ensure breakouts are prevented.

• Accurate mapping and GPS locations of infestations within the Wetlands will assist in targeted management and recording of success in removal efforts.

• The goal of control should be to incrementally reduce the levels of infestations over a period of 2 years to 25% or lower of the extent in mid-2015, and to have negligible occurrence of Hydrocotyle in the Wetlands at the end of 3 years (2017).

Zone 2a – Canning River Main Channel and shorelines – upstream of Kent Street Weir to Nicholson Road Bridge

Highest • Continue surveillance by vessel and by foot on riparian areas at bi-monthly frequency, or if resources permit, monthly. Record any infestations on GPS. Manually remove all small colonies up to 1.0 m2, mark the locations with a marker, and measure how much is removed. Re-visit sites where manual removal has been conducted using GPS location or markers.

• Reduction of Typha stands to access Hydrocotyle is not required in the riparian areas of the northern bank, as inspections can occur from both water and land.

• Reduce Metsulfuron treatments to 3-4 times per 12-month period. Use either the quarter rate or standard rate depending on the presence of native flora and fauna. Spot-spray of small volumes only, applied either from a boat or from back-back. Treat in spring and summer when plants are actually growing and adhere to all precautions and guidelines of herbicide use in aquatic environments (in or around water). Motorised spray treatments are not needed as current infestation levels are low to very low.




• Other non-chemical techniques that can be used include placing several layers of shade cloth over a small patch and pegging to reduce its vigour prior to manual removal after about a week or two.

• There is a rich diversity of sedges and other native species in the lower and upper riparian areas on both sides of the River channel. Therefore, any control activity must be undertaken with care, not unduly trampling on existing vegetation.

• The goal should be to have nil or negligible occurrence of Hydrocotyle on the main River on both sides and in the lower riparian zones in the reaches upstream of the Kent Street Weir to Nicholson Road Bridge within the next 6-12-months.

Zone 2b – Canning River Wetlands and Lagoons on the southern side

Medium • Management of Hydrocotyle in the southern wetlands and lagoons is difficult because of access. Most infestations are in slushy mud on sediments that have accumulated around the base of Melaleuca trees and extend out. Safety to operators must be a paramount consideration in accessing these for control. Hydrocotyle populations are mostly low-level infestations, probably due to the shade of the trees. Although well contained, there is potential for further downstream spread from these locations in heavy wet weather.

• Manual removal should be undertaken by suitably trained staff, possibly using small boats or kayaks to reduce the larger biomasses entrenched around the base of trees. The current levels of infestation indicate that several rounds of manual removal, conducted monthly, prior to the growing season, may reduce infestations to a large extent. Where circumstances dictate, chemical treatment may precede manual removal. Accurate mapping and GPS locations of infestations within the Wetlands will assist in targeted management and recording of success in removal efforts.

• Some reduction of Typha stands may be necessary to access Hydrocotyle in some of the riparian areas, which are otherwise inaccessible. A small machine (Truxor) could be used to create access in boggy areas, not accessible otherwise. Access can be from both water and land. Where access may be achieved by brush-cutters and chain-saws, such equipment should be used, as required.

• If herbicide treatments are to be used – Biactive® Glyphosate is recommended for wetland areas where there is no risk of damaging native plants. Infestations underneath Melaleuca trees, in open water, can be readily treated with Biactive® Glyphosate spot sprays with a high level of efficacy and success guaranteed.

• If selectivity is required, Metsulfuron could be used. Reduce Metsulfuron treatments to 3-4 times per 12-month period and use either the quarter rate or standard rate depending on the presence of native flora and fauna. Spot-spray of small volumes only, applied either from a boat or back-back. Treat in spring and summer when plants are actually growing and adhere to all precautions and guidelines of herbicide use in aquatic environments. Motorised spray treatments are not needed as current infestation levels are low.

• The goal should be to have nil or negligible occurrence of Hydrocotyle in the Wetlands on the southern side of the River channel within the next 6-12-months.




Zone 3 – Drainage Infrastructure

Highest • Continue surveillance by foot within channels where some minor infestations may occur on the edges, as in the past. Surveillance should be at a minimum bi-monthly frequency (6 events per year). If required, this frequency should be increased to monthly inspections. Record any infestations on GPS.

• Inspections should cover areas where historical infestations have occurred, as well as new areas where there may be downstream spread;

• Undertake manual removal of all small colonies up to 0.1 m2, mark the locations with a marker and measure how much is removed. Re-visit sites where manual removal has been conducted using GPS location or markers.

• As part of manual removal, consider the possibility of fragment dispersal downstream. If required, place barriers (boom or netting) to capture fragments prior to manual removal, and collect any dispersed pieces.

• Fragment dispersal in channels could occur in wet weather. Therefore, only undertake manual removal during dry periods.

• If herbicides are needed, the preference should be Biactive® Glyphosate where selectivity is not an issue. Glyphosate will also allow other problematic species to be opportunistically treated and controlled.

• Where selectivity is required Metsulfuron may be used; however, reduce Metsulfuron treatments to 3-4 times per 12-month period, and use either the quarter rate or standard rate depending on the presence of native flora and fauna. Spot-spray small volumes only, and apply from back-back. Treat in spring and summer when plants are actually growing and adhere to all precautions and guidelines of herbicide use in aquatic environments. Motorised spray treatments are not needed as current infestation levels are low. Expect all treated patches to be dead within about a month after treatment.

• The goal should be to have nil or negligible occurrence of Hydrocotyle in the drainage channels within the next 6-12-months.

Zone 4 – Bannister Creek

Highest • Continue surveillance by foot within channel where some minor infestations occur in slushy mud. Inspections should be at a minimum bi-monthly frequency (6 events per year). If required, this frequency should be increased to monthly inspections.

• Inspections should cover areas where historical infestations occurred, as well as new areas, where there may be downstream spread.

• Record any infestations on GPS. Manually remove all small colonies up to 1.0 m2, mark the locations with a marker, and measure how much is removed. Re-visit sites where manual removal has been conducted using GPS location or markers.

• No herbicide treatments are necessary, as current infestations are low and near eradication. Manual removal is probably sufficient to control any new or remaining colonies. However, surveillance should continue after manual removal.

• The goal should be to have nil or negligible occurrence or eradication of Hydrocotyle in the Creek within the next 3-6 months.




Zone 5 – Collier Pines Drain at Bodkin Park, Waterford

Highest • Continue surveillance by foot. Inspections should be at a minimum bi-monthly frequency (6 events per year). If required, this frequency should be increased to monthly inspections.

• Inspections should cover areas where historical infestations have occurred, as well as new areas where there may be downstream spread.

• Record any infestations on GPS. Manually remove all small colonies up to 1.0 m2, mark the locations with a marker, and measure how much is removed. Re-visit sites where control has been previously achieved.

• No herbicide treatments are necessary, as current infestations are low and near eradication.

• The goal should be to have eradication of Hydrocotyle in the Creek within the next 3-6 months.

Note: flexibility of approaches is required in implementing the recommendations given in Table 7. There are no hard and fast rules when it comes to attempting control of major aquatic weed infestations. If the physical control methods are not achieving the desired reduction of Hydrocotyle infestations, other methods should be tried. Whilst excessive herbicide use is not favoured, diligent use is regarded as an essential tool in managing deeply-entrenched Hydrocotyle infestations. It some situations, Hydrocotyle may not be completely controlled by non-chemical methods, because of site constraints, discussed previously, and adjustments to the Plan may be required.


5.9 Considerations and Opportunities

Considerable funds, effort and awareness raising activities previously carried out in the region mean that there has already been some impetus in managing Hydrocotyle. This should be capitalised upon.

The high value of recreational industries in the Canning River Regional Park, Canning River itself and associated natural areas, wetlands and built environment suggests there may be opportunities for contribution of future funds for management (if required) or for monitoring from various stakeholders. The stakeholder groups need to be carefully targeted in awareness/education/caution campaigns.

Considerable urban growth across the region presents a threat of spread through earth-moving activities, and an opportunity exists to get Hydrocotyle included in the development application process, and/or parkland and natural area management operational plans. Consideration could be given to possible contributions by urban developers (and associated earth-moving companies).

The education/awareness factor is probably as great an issue in preventing future spread, as well as controlling existing infestations. Spread is often from human action that could be prevented. Opportunity exists for major gains through educational campaigns.

Hydrocotyle has the potential to spread much more widely than it currently occurs. Therefore, prompt action is required and all infestations need to be diligently treated with a focus on effective techniques and outcomes.

Ongoing investigations into biological control agents continue overseas. Similarly, effective herbicides for all situations are not available for use in Australia. Until more successful agents can be found, imported, raised and released, or more effective herbicides found, it is important to keep existing infestations to a manageable level.

Hydrocotyle is not a very interesting topic for newsworthy articles. Media campaigns need to find other “hooks” to engage reader interest. It has been suggested articles should cover positive, success story aspects of Hydrocotyle management rather than gloom and doom or regulatory issues.

Adequate resourcing remains the major barrier to the effectiveness of Hydrocotyle management and control in the region.

5.10 Management Goals, Actions and Responsibilities

The management actions and performance expectations of the Hydrocotyle WMP with implementation responsibilities are given in Table 8


Table 8 Management Goals, Action and Responsibilities for the Hydrocotyle WMP

Goal 1: A collaborative framework is in place to promote all stakeholders working together in an integrated manner to manage Hydrocotyle infestations and new outbreaks in Canning River and adjacent waterways and wetlands

Actions Performance Indicator Responsibility

1.1. Hydrocotyle Working Group/Committee structure maintained and supported, and links developed and maintained with all stakeholders

Working Group/Committees meet regularly through the year. Links forged with Stakeholders

All stakeholders represented on Working Group/Committee

1.2. The Hydrocotyle Working Group/Committee actively and regularly communicate on Hydrocotyle issues, particularly new infestations and in cooperative management situations

Hydrocotyle management issues are discussed and outcomes forwarded to other stakeholders

All relevant government agencies and stakeholders

1.3. The Hydrocotyle Working Group/Committee actively involves other stakeholders in Hydrocotyle management issues, particularly other levels and spheres of government (i.e. infestations on public land), and in awareness raising and community activities.

Committee to report on education /awareness/involvement activities and their results twice per year


1.4. Best practice forums are held regularly to maintain currency among all councils about the most effective strategies against Hydrocotyle. Notes from these, together with research findings, become the basis for a Current Recommendations Guide that can be used by all stakeholders.

Annual forum held to update all on current situation, experiences and opportunities.

Outcomes compiled into document for circulation.


Assign responsibility to one (Lead) agency

Goal 2: An overall reduction in the extent and intensity of infestations is achieved and eradication from some locations.

2.1. Control programs on existing infestations and any new incursions are maintained to contain or eradicate weed populations.

Councils and regional committees continue to update and implement Hydrocotyle control plans


2.2. Control programs continue to utilise integrated management techniques where appropriate and apply environmentally sound practices.

Appropriate technologies suggested are applied and reported on; variations brought to the notice of the Committee for discussion.


2.3. Existing infestations are mapped and prioritised on a site-specific basis to an agreed system developed through committee consultation (This has been proposed in Table 7)

Prioritising system developed through consultation, and implemented.

Survey results entered onto single database



Table 8 (cont.) Management Goals, Action and Responsibilities for the Hydrocotyle WMP

Goal 3: Further spread of the weed beyond current boundaries is effectively prevented.


3.1. Known dispersal mechanisms recorded and actions taken to prevent recurrence by managing vehicles of spread.

Sources of new infestations are recorded and disseminated. Actions noted (see 3.8.)


3.2. Effective strategies to address dispersal mechanisms developed collaboratively and implemented across the region.

System to address sources in 3.1. above developed collaboratively with stakeholders


3.3. Education and awareness material developed for target audiences identified in 3.1. above, and disseminated widely in all regions.

Education components of the Hydrocotyle WMP implemented and reported on annually. Gaps identified and incorporated into future plans.


3.4. Areas at risk of spread of Hydrocotyle are located and regularly monitored. Annual survey of at-risk areas carried out and reported on.


3.5. Surveillance for new infestations is maintained. Surveying of at risk sites at least once annually. All stakeholders represented on Working Group/Committee

3.6. Awareness/identification training for Council staff and Volunteers provided through Councils to facilitate greater incidence of reporting and reduce accidental spread.

Weed identification training for staff provided in all Councils where Hydrocotyle known or suspected.


3.7. Contingency plans developed and disseminated for rapid response to emergency situations (flood or other massive spread/dispersal event).

Flood contingency plan developed, based on prior experiences.

All stakeholders represented on Committee

3.8. Protocols developed to address emerging problem and new situations; Examples include vehicle and machinery hygiene, earthmoving checklist, required signage for all infestations, procedures for addressing new infestations in aquatic and terrestrial sites, accidental mass movement etc.

Protocols developed in consultation with experts.

Committees then support adoption procedures through council processes.


3.9. All reported new or possible infestations are rapidly followed up by inspection and appropriate action.

Inspection to occur within 2 weeks of initial report. All stakeholders represented on Working Group/Committee

3.10. All new infestations are reported to the appropriate authority and recorded on the State database maintained by the Lead Agency.

All confirmed new infestations reported to the central database within 2 weeks.



Table 8 (cont.) Management Goals, Action and Responsibilities for the Hydrocotyle WMP

Goal 4: All stakeholders are involved in cooperative effort against Hydrocotyle incursions on both public and private land. This includes implementation of effective education and awareness programs.


4.1. Coordinated media campaign highlighting positive outcomes and addressing risk situations waged at regular intervals to maintain interest and currency.

Each stakeholder agency/group produces at least one targeted media or education piece annually


4.2. Land managers and users in problem areas become aware of the threat of Hydrocotyle through education and awareness, training or media programs to ensure timely identification of the weed and prevent accidental dispersal.

Ongoing targeting of at-risk properties with explicit information material carried out.


Goal 5: New technologies and management options, advised through research and development, are supported and promoted in the management of Hydrocotyle in the region.

5.1. Research findings and advances in technology for Hydrocotyle management are widely circulated amongst weed managers and incorporated into management plans.

Open information exchange maintained between research conducted in Australia, and overseas with updates provided at meetings.

All stakeholders represented on Working Group/Committee; Lead Agency to lead.

5.2. Herbicide registration changes and permits for specific herbicide use on Hydrocotyle are notified across the region and State through the relevant Government Agency.

Any new permits or changes to registrations for herbicides for Hydrocotyle notified at committee meetings

Department of Agriculture & Food, WA

5.3. New or additional protocols developed to improve management systems are supported.

Weed Officers adopt protocols, and their adoption by wider stakeholders promoted and supported.


5.4. New control opportunities are exploited where available, and their effectiveness incorporated into management strategies.

Management plans to include new and emerging control options, particularly as advances made through research and experience.

All stakeholders represented on Working Group/Committee; Lead Agency to lead.

5.5. The full range of options, including physical and mechanical removal, incorporation of judicious herbicide use and community involvement is explored in implementing the management strategies for Hydrocotyle.

Outcomes of best practice forums applied where applicable across the region.



5.11 Implementation Schedule

The implementation schedule proposed for the Hydrocotyle WMP is initially three years. Given the high degree of success that has been achieved, the targeted control in infested areas, and in some cases, eradication, can be achieved in the next three years. Monitoring of infested areas need to be undertaken for much longer – probably a 5-10 year time frame.

Annual performance reviews (proposed) allows the opportunity to review the WMP and make any adjustments, and incorporate any new developments (such as the planned developments associated with the Kent Street Weir and its operations).

Specific implementation schedules for different stakeholders are best developed when the WMP is adopted by the stakeholders, and a Lead Agency takes charge of plan implementation.

5.12 Training

Management of aquatic weeds, such as Hydrocotyle, requires training of staff, both operational staff and those who are involved in supporting activities, such as surveys, mapping and planning in holistic catchments and waterways management.

There are other aquatic weeds, which also require similar attention and management approaches, which involve upstream catchment management. Identification of aquatic weeds, methods of water quality management and environmental protection issues are also an integral part of the training required by staff who are to be involved in future management.

Training has been identified as an important component of implementing the Hydrocotyle WMP Goal 3. Training in aquatic plant management approaches, including Hydrocotyle, should be provided to the relevant people as a half-day or one-day workshop in an interactive environment.

5.13 Monitoring and evaluation

Monitoring and evaluation is essential to the continued development of the strategy to gain efficiencies and to obtain best results. It may require up to 3% of the control budget.

Evaluation would include assessing changes in distribution of the weed (current versus potential), determining efficacy of the various control techniques and their integration, determining changes in rate of spread, frequency of locating new infestations, and assessments of the costs and benefits of the strategies.

Whilst regular inspections and monitoring should be done on an on-going basis (once every 2-3 months), more comprehensive monitoring and reporting should be done at minimum of a yearly cycle. This will give an evaluation of the effectiveness of current control methods, and also allow a comparison with methods and programs which were used in the past.

Given the history of Hydrocotyle, their seeds and fragments can remain in the soil for many years; so even in areas where previous weed patches existed, which are thought to be eradicated, must be monitored for some time, after the last plant has been sighted.

The following should be an integral part of implementing the Hydrocotyle WMP:

Annual reporting on implementation, particularly with regard to Federal funding.

Report to be compiled by the Lead implementing agency and submitted to the Hydrocotyle Working Group and then to all stakeholders, with reporting on achievement of each action;


Annual survey of Hydrocotyle populations recorded on a central database and report of comparison with previous years made; and

Review of the Plan in 2018 (after 3 years). Changes to be collaboratively developed through the Working Group and other stakeholder inputs.

This strategy is subject to 3-year cycle of review. The Hydrocotyle Working Group, as a component of its meetings, will monitor the implementation of the plan. Annual reports will be made available to relevant stakeholders.

5.14 Performance indicators

The performance indicators that would be used in relation to Hydrocotyle control include:

No new importations of Hydrocotyle in to Western Australia;

Increased awareness of Hydrocotyle by the community and aquarium industry, horticultural suppliers and nurseries;

Increased reporting rate of new infestations;

Improved understanding of the social, economic and biodiversity impacts of the weed;

Improved understanding of biology and ecology of the weed;

Better treatment packages for eradication of small infestations;

Reduced rate of spread;

No new infestations reported; or a decline in the number of small infestations in the Canning River Sub-Catchments and the region, in general;

Effective collaboration and partnerships established between government agencies and catchment groups and volunteers;

Collaboration and co-operation with community resulting in better education, surveillance and control;

Personnel trained in aquatic plant management and control techniques, relevant to managing risks posed by them;

5.15 Benefits

Increased awareness and the ability to identify and rapidly report new Hydrocotyle incursions should lead to improved control of new outbreaks.

Ongoing diligence in implementing Hydrocotyle control programs will protect the valuable environmental assets associated with the Canning River and the Canning River Regional Park, and significant recreation facilities of the Rivers.

Hydrocotyle threatens the integrity of natural ecosystems where it manages to establish. The success of the historical control programs illustrate the environmental, social and economic benefits accrued from effective, persistent activities, even in difficult wetland situations. However, aquatic weed management programs are expensive, and protection of aquatic systems to prevent Hydrocotyle introduction through assiduous monitoring and rapid action is preferred.

5.16 Lead Implementer – ‘Hydrocotyle Working Group’

Building on previous experience and established collaborative partnerships, the Hydrocotyle Working Group should be the key community and agency stakeholder group that should implement the Hydrocotyle WMP in the Canning River region.


The membership is comprised of the major stakeholders that could drive the program and includes the following:

At least one representative from SERCUL;

At least one representative from the Department of Parks & Wildlife;

At least one representative from the Swan River Trust (now part of DPaW);

At least one representative from the City of Canning;

At least one representative from the City of South Perth;

At least one representative from Water Corporation;

At least one representative from the Wilson Wetlands Action Group (WWAG); and

At least one representative from the Canning River Regional Park Volunteers

Other stakeholder agencies and/or committed volunteers or weed control contractors, consultants or operators could be added to the Group, as required.

5.17 Stakeholder Roles and responsibilities

In addition to the co-ordination of actions, defining the roles and responsibilities of individual stakeholders is critically important in further reducing the Hydrocotyle infestations and the threat posed by similar aquatic species. Table 9 provides a list of roles and stakeholder responsibilities that should be agreed upon and carried out. The progress on these activities is proposed to be monitored by the Lead implementation agency.

Table 9 Summary of Stakeholder Roles and Responsibilities

Stakeholder Responsibilities

Local and State Government Agencies and Departments

• Ensure that Hydrocotyle is identified in all Local, Regional and State-level pest management plans;

• Liaise with landholder, community and industry interest groups to coordinate management and control;

• Continue to implement effective and appropriate ‘best practice’ control techniques;

• Provide extension and education services to urban and industry stakeholders;

• Support enforcement of legislation and control measures;

• Undertake pro-active inspections and reporting of Hydrocotyle infestations.

Water, drainage; Irrigation Authorities

• Monitor the infrastructure and assets for Hydrocotyle and report any findings to Working Group and Lead stakeholders;

• Continue to implement effective and appropriate ‘best practice’ control techniques;

• Identify and reduce contributions to nutrient loading from urban infrastructure, such as stormwater drains;

• Contribute funds to research improved integrated control techniques.

Landcare Catchment Management Groups

• Monitor the catchment for Hydrocotyle and report any findings to Working Group and Lead stakeholders;

• Identify and reduce contributions to nutrient loading from septic systems, livestock, garden run-off and urban development etc;

• Seek funding for waterways and catchment health management programs.

• Develop and employ hygiene protocols for local infestations;


Table 9 (cont.) Summary of Stakeholder Roles and Responsibilities

Stakeholder Responsibilities

Conservation Groups

• Improve identification skills of members;

• Promote awareness of Hydrocotyle impacts on freshwater ecosystems;

• Monitor water bodies and report infestations of Hydrocotyle;

• Assist in Hydrocotyle control in a co-ordinated way with Working Group

Recreational Groups

• Ensure members are aware of Hydrocotyle and can identify it;

• Educate members on quarantine and weed hygiene protocols and not to undertake recreational activities or actions that will spread Hydrocotyle;

• Practice weed hygiene on recreational equipment (boats, nets etc);

• Help monitor water bodies and report infestations of Hydrocotyle.

Aquarium industry

• Ensure the aquarium industry continues to improve its responsibility for not introducing aquatic species that may become invasive species in Australia;

• Create awareness amongst their members of the legislation on weeds and particular problems that can arise with aquatic species sold for aquaria and ponds.

Private Landholders

• Prevent the introduction of Hydrocotyle onto their lands and waterfront properties;

• Alert Working Group and lead stakeholders if Hydrocotyle is found;

• Seek assistance and manage infestations on their own land/water and eradicate infestations where feasible.

5.18 Re-evaluation of the Hydrocotyle Management Plan

All plans should have definite timelines for review and updating depending on the assessment of results achieved under the plan at any given time. An annual review is likely sufficient and should be planned to occur in a timeframe, so that the implementation of the Plan is assessed critically before the next growing season.

The Management Plan may have to be modified depending on the actual results of tried control methods, which did not achieve expected results. However, it should be regarded as a Tool to achieve better outcomes over a given period of time.


6. References APVMA (2012). Permit to allow Minor Use of an AGVET Chemical Product for the Control of

Environmental Weeds in various Situations. Permit No. PER 13333 (Valid from 2 March 2012 to 31 March 2017). Issued to Department of Agriculture and Food, Western Australia.

Appleby N. (1997). Survey report on the existence of floating pennywort (Hydrocotyle ranunculoides) along the River Wey and Wey Navigation. Centre for Aquatic Plant Management Report. Wallingford, UK: CEH Wallingford.

Bidwell, J. R. and Gorrie, J. R. (1995). Acute Toxicity of a Herbicide to Selected Frog Species. Department of Environmental Protection, Western Australia.

Boyd, C. E. and Bayne, D. R. (1988). Use of Water Hyacinths (Eichhornia crassipes) and Water Pennywort (Hydrocotyle ranunculoides) in treatment of poultry waste. Department of Fisheries and Allied Aquacultures. Auburn University, Alabama.

CABI (2015). Centre for Agriculture and Biosciences International. Invasive Species Compendium. Hydrocotyle ranunculoides (Floating Pennywort) Datasheet. http://www.cabi.org/isc/datasheet/28068 Date of access: 20/07/2015.

CRC (2005). Cooperative Research Centre for Australian Weed Management. Herbicides: Guidelines for Use in and around Water.

DiTomaso, J. M., Kyser, G. B. et al. (2013). Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California, 544 pp.

Donahue, R. (1994). Impact of the Hydrocotyle removal program in the Canning River. Swan River Trust. Unpublished Report. Perth, WA.

Duenas, M.A. and Newman, J.R. (2010) Hydrocotyle ranunculoides growth dynamics and implications for management. Paper presented to the 42nd Robson Meeting, 9th-10th February 2010.

EFSA (2007). European Food Safety Organisation: Opinion of the EFSA Scientific Panel on Plant Health on request 11 from the Commission on pest risk analysis made by EPPO on Hydrocotyle ranunculoides L. f. (floating pennywort), The EFSA Journal 468:1-13. (http://www.efsa.eu.int/EFSA/efsa_locale-1178620753812_1178638747194.htm)

EPPO (2006). European Plant Protection Organisation: Hydrocotyle ranunculoides. EPPO Bulletin 36: 3-6.

EPPO (2009). European Plant Protection Organisation: Pest Risk Analysis for Hydrocotyle ranunculoides. 63 p. Unpublished.

Government of WA (2001). Water Notes for Rivers Management. Water and Rivers Commission. WN22, Advisory Notes for Land Managers on River and wetland Restoration. Herbicide Use in Wetlands. April 2001

Government of WA (2007). Department of Health WA. Circular No. PSC 88: Use of Herbicides in Water Catchment Areas.

Government of WA (2015). Department of Agriculture and Food Website: https://www.agric.wa.gov.au/declared-plants/declared-plant-control-table

Hussner, A. and Lösch, R. (2007). Growth and photosynthesis of Hydrocotyle ranunculoides L.fil. in Central Europe. Flora 202: 653-660.

http://www.cabi.org/isc/datasheet/28068



Hussner, A., Denys, L. and van Valkenburg, J. (2012). NOBANIS – Invasive Alien Species Fact Sheet – Hydrocotyle ranunculoides – From: Online Database of the European Network on Invasive Alien Species – NOBANIS www.nobanis.org Date of access: 20/07/2015.

Klemm, V. V, Siemon, N. L. and Ruiz-Avila, R. J. (1993). Hydrocotyle ranunculoides: a control strategy for the Canning River Regional Park. Swan River. Trust Report, No. 6.

Mann, R. (1998), Acute Toxicity of Herbicide- Formulation Surfactants to Four Species of Western Australian Frogs. Report prepared for the Water Corporation of Western Australia, Curtin University of Technology, Western Australia.

Marchant, N. G., Wheeler, J. r., Rye, b. L., Bennet, E. M., Lander, N. S. and Macfarlane, T. D. (1987). Flora of the Perth Region. Western Australian Herbarium, Department of Agriculture, Western Australia. 1080 pp.

McChesney, C. (1994). Literature Review of the Genus Hydrocotyle L. (Apiaceae) with particular emphasis on Hydrocotyle ranunculoides L.f. Swan River Trust Report No. 18.

Moore, J. H. and Fletcher, G. E. (undated), Environmental Effects of Herbicides. Agricultural Department of Western Australia.

Newman, J. R. (2006). Centre for Ecology & Hydrology (CEH), Natural Environment Research Council, Aquatic Plant Management Group. Information Sheet 24: Floating Pennywort (Hydrocotyle ranunculoides). 4 pp.

Newman, J. R. and Dawson, F. H. (1998). Ecology, Distribution and Chemical Control of Hydrocotyle ranunculoides in the UK. Proceedings 10th European Weed Research Society (EWRS) Symposium on Aquatic Weeds, Lisbon, 389-392.

Newman, J. R. and Duenas, N. A. (2010). Information Sheet: Controlling Floating Pennywort (Hydrocotyle ranunculoides). Aquatic Plant Management Group. Centre for Ecology & Hydrology. CEH Wallingford, Crowmarsh Gifford, Wallingford, Oxon, OX10 8BB.

Newman, J. R., Shaw, R. and Deunas, M. A. (2009). Hydrocotyle ranunculoides L.f. – Origins and Control Options. Proceedings 49th Annual Meeting, Aquatic Plant Management Society, 12-15 July, 2009, Milwaukee, Wisconsin.

PMEP (1999). Pesticide Management Education Program. Extension Toxicology Network – herbicide toxicology data. Extension Toxicology Network (EXTOXNET). Cornell University extension services, USA. http://pmep.cce.cornell.edu/profiles/extoxnet/

Pierce, J. R. and Raynor, B. (1992). Chemical Control of Aquatic Weed Hydrocotyle ranunculoides. Preliminary report on results obtained from experiments conducted under glasshouse conditions. Department of Agriculture, West Australia. 34 pp.

Pierce, J. R. and Raynor, B. (1994). Hydrocotyle: Chemical Control with Diquat. Report prepared for the West Australian Agriculture Department, Western Australia.

Ruiz Avila, R. J. and Klemm, V. V. (1996). Management of Hydrocotyle ranunculoides , an aquatic invasive weed of urban waterways in Western Australia. Hydrobiologia, 340, 187–190. (Proceedings of

SERCUL (2014). South East Regional Centre for Urban Landcare. Urban Waterways Renewal Project. Report prepared for the Department of Water. 78 pp.

Swan River Trust (1996). Hydrocotyle: A review of research and control. Swan river Trust, Unpublished Report.

http://www.nobanis.org/

http://pmep.cce.cornell.edu/profiles/extoxnet/


van der Burg, W. J. (2010): Effect of hydrogen peroxide spraying on Hydrocotyle ranunculoides L.f. survival. An initial experiment. Plant Research International, Wageningen, 6 pp.

van der Burg, W. J. and Michielsen, J. M. (2010): Effect of flaming on Hydrocotyle ranunculoides L.f. survival. An initial experiment. Plant Research International, Wageningen, 8 pp.

Webster, F. J. (1994). The Biology and Ecology of Hydrocotyle ranunculoides. Honours Thesis (Unpublished). Botany Department. University of Western Australia. Perth. 103 pp.

Webster, F. J. (1995). Aspects of the Biology and Ecology of Hydrocotyle ranunculoides. Unpublished Report to the Swan River Trust. March 1995.

WWAG (2015a). Wilson Wetlands Action Group, Urban Bushland Council Inc. (Source: http://www.bushlandperth.org.au/member-groups/4-south-of-the-river/80-wilson-wetlands-action-group.

WWAG (2015b). Wilson Wetlands Action Group. Proposal to control and remove Hydrocotyle on The Trustees of the Christian Brothers Land in Wilson Wetlands (Wilson 2). Dated 18 August 2015.

http://www.bushlandperth.org.au/member-groups/4-south-of-the-river/80-wilson-wetlands-action-group-


GHD | Report for Hydrocotyle Weed Management Plan - For the Middle and Upper Canning River, 23/15602

Appendices


Appendix A – Summary of the Outcomes of Consultation with Stakeholders

Vision

Stakeholders were asked to provide their organisation’s ultimate vision for Hydrocotyle management in the Canning River. The following two key visions were shared by all:

Eradicate Hydrocotyle from the Canning River; and

The continuation of positive, enduring stakeholder collaboration in managing Hydrocotyle in the Canning River.

Additional goals of stakeholders include:

Investigate non-herbicide control methods;

Keep the community empowered to continue to keep delivering for the benefit of the Canning River environment;

Greater community awareness and education;

Community enjoyment of the river environment;

Management plan operating as the benchmark for aquatic weed management.

Performance Measures

Stakeholders were prompted to provide performance measures for the Project, guided by agreed upon objectives. These objectives included:

Work with the local Landcare community to identify the weed management priorities in the middle and upper Canning River;

Develop and implement a strategic approach to priority weed management in the middle and upper Canning River based on the community consultation above

Ensure the SCRR Priority Weed Management Program aligns to and complements other SCRR programs including the Hydrocotyle Management Plan, Hydrocotyle Management Program and the SCRR Direct Community Action program

Key messages and performance measures concerning these are detailed as followed:

1. The WMP should utilise both science and stakeholder feedback to refine weed management priorities in the Canning River regions (stakeholders include the local Landcare, community, government and other stakeholders);

2. The WMP should include specific priorities and approaches for specific locations and management areas;

3. The final WMP should include recommendations that are supported by a majority consensus of the Hydrocotyle Working Group;

4. The WMP should consider a strategic 10 year approach to priority weed management in the middle and upper Canning River;

5. The WMP should recognise and work in alignment with the Hydrocotyle Management Program and the SCRR Direct Community Action program.

6. The WMP to review and build on previous investigations and management plans for the affected areas.


Additional performance measures that did not relate specifically to project objectives were also identified by stakeholders. These are for the Hydrocotyle WMP to include:

1. A stakeholder engagement plan that can be translated into an enduring open communication plan that allows all stakeholders to feed in and share information on management activities, challenges and successes.

2. Targeted recommendations for the first year and a strategic framework for future management and budgeting beyond the current funding programme.

3. Site specific recommendations and sufficient strategic guidance to also be applicable to other infestation areas.

Project Issues

Conversations between key stakeholders concerning current or potential project issues formed a part of the Stakeholder Alignment Workshop. Issues were identified alongside potential strategies for mitigation. The outcome of this discussion is provided below in Table 10.

Table 10 Key Issues and Strategies

Issue Strategy

Management across borders and jurisdictions

• Ongoing stakeholder communication between all land and waterway managers to ensure collaborative, consistent efforts.

Typha / other weeds control • Management plan needs to consider site specific benefits to control of other weeds, such as Typha.

Weeds provide habitat and food and vital habitat for

• WMP to consider Hydrocotyle providing food and refuge to macroinvertebrates, native fish species and other vertebrates.

Water quality prevents other submerged aquatics from growing

• Stakeholders to share water quality data; Swan River Trust website includes data for monitoring sites; WWAG can provide bore references for site specific data.

• Management to consider other aquatic native species to provide replacement habitat (Ribbon grass, Otelia)

Acid Sulphate Soils in some areas

• Management plan to acknowledge occurrence in some areas (i.e. Wilson Wetlands).

Safety in Herbicide use

Safety in Accessing Wetlands and Lagoons / hazards

• WWAG has protocols and equipment;

• Working in water and working from canoes policies;

• Site specific Job Safety Assessments;

• Management plan to consider risk assessment for key hazards

Access to the weed infestations

• Management plan to recommend how to access infestations to undertake control activities, where access is difficult

Monitoring • Photo-point monitoring to be included in Management Plan

Independent control by stakeholders

• Ongoing stakeholder communication between all waterway managers to ensure collaborative and consistent efforts.

Priorities • Recognise that ‘prioritisation’ often relates to whether funding is available. Whatever is funded becomes the priority (i.e. Mill Drain (Water Corp), Collier Man Drain within Bodkin Park (CoSP).

• Many management actions have been successful; in some areas Hydrocotyle is close to being eradicated (i.e. Bannister Creek


Appendix B – A Summary of Key Issues raised in Stakeholder Discussions Table 11 Summary of Discussions with Stakeholders

Stakeholder Discussion notes

SERCUL

Matt Grimbly

Brett Kuhlman

Discussed the broad program; encouraged Matt to write up the history of treatments; was informed about the mapping that had been conducted in March-April 2015; results of excellent control obtained in Mill Street drain; long-term management or co-ordinated action – probably best through one organisation; agreed that 10 years was too long; 5-years more likely; eradication is the goal, probably achievable with the well-funded program if treatments occur regularly; Matt suggested monthly inspections and spot treatments with Metsulfuron (quarter dose) plus 1% glyphosate.

Michael Cobby

Department of Parks & Wildlife (DPAW)

Discussed the broad program; DPAW owns and manages much of the “Canning River Regional Park” land areas; manages from Nicholson Bridge to Canning Bridge; broadly, DPAW has no allocated funds to manage H. ranunculoides in the areas of the Park. WWAG manages the Wilson Wetlands, which are in the Regional Park lands; Swan River Trust provides funds to manage aquatic weeds up to 2 m from river (Riparian Zone);

Needs funds to manage H. ranunculoides in Park lands; has to use contractor from the Panel; has been using Nathan/Bunyip; SERCUL could be that contractor; favour Typha reduction as a means to get access; has no objections to using mechanical equipment, such as a “Truxor” to create access ways through Typha; burning Typha – highly unlikely at this stage; Receives a great deal of support from Community Groups (such as from Jo and Richard Stone) to manage Park lands;

Matthew Box

City of Canning

Discussed the broad program; hardly any H. ranunculoides in Bannister Creek; we may have seen a different species - Hydrocotyle muricata in the creek; H. ranunculoides is not a major problem for the areas managed by The City of Canning; it is a State ‘declared’ weed; not “WoNS”; there is some concern about herbicides in waterways; Metsulfuron persistence and surfactant issues; used “Pulse” penetrant in a riparian area to kill off a small population (100% success); agreed that a program over the next few years (5-years more likely) could achieve eradication, which is the ultimate goal.

Jo Stone/

Richard Stone

Community Group volunteers in bushland and weed management; have been actively managing riparian weeds and associated riparian vegetation for decades; (“Every weed is a native somewhere”); understand ecological issues and processes; want to promote nutrient reduction schemes in urban areas; education and awareness by community are so important; herbicides in water are a concern; therefore, a balance of herbicides and other methods (manual removal) would be best – where this is possible (small colonies); funding would be useful to have to continue managing parkland areas. (Is funding sought for Hydrocotyle control?)

Russel Gorton, WWAG

Discussed the broad program, and specifically Wilson Wetlands 1 and 2; conservation values; environmental risks highlighted; WWAG has funding to study the effects on Hydrocotyle of (ebb and flow) of tidal movements; impacts from ground water; saline seepages and fresh water discharge (located at the confluence in Lot 4 in Wilson 2, Castledare). The results aim to provide recommendations to all stakeholders as to how Hydrocotyle could be managed in the future using no herbicide, but by simply making controlled adjustments to the water level and potentially adjusting its fresh water state to a slightly more saline state to eradicate Hydrocotyle using natural processes; needs funds if available; studies are underway on growth rates, etc.


The two facilitated Workshops conducted provided the opportunity for the stakeholders to participate in small group conversations on major points and issues where there were notable differences of opinion. The outcomes are summarised below in Table 12.

Table 12 Summary of Discussions with Stakeholders at Workshops

Issue Discussion notes

Non-chemical methods

Discussions centred on: (a) What is achievable with non-chemical methods; (b) What is preferred? (c) Do these methods have application in conservation area?

There was agreement that non-chemical methods were preferred to herbicides, although the effectiveness of some available methods was not established. The consensus was that non-chemical methods will not be successful on their own. Also, more research is needed on various methods, and these do not fit with the time-frame of implementation of the WMP, given the current availability of funding and stakeholder expectations. • Salinity: There was no agreement on the applicability of salinity management as a

management tool, despite clear evidence that salinity kills Hydrocotyle, which is essentially a freshwater species. Whether it is possible to improve salinity intrusion into Wilson 1 and Wilson 2 through pumping, or by creating a channel is uncertain and these remain options for the future.

• Nutrient reduction: There was agreement that this is important, but not specifically to achieve the WMP goals. Upstream stormwater management in the urban sub-catchments is already occurring; nutrient reduction in the inflows may not be achievable in the time-frame for Hydrocotyle control.

• Steam: Considerable interest in using steam as a tool; this may have application in some areas, but not in boggy and wet terrain. GHD took note of the interest and possibility of trialling the method in some areas.

• Revegetation and shading with native plants: the consensus was not to revegetate any areas until all Hydrocotyle has been eradicated (the local experience and research indicates that shade does not reduce Hydrocotyle).

• Typha: Does not keep Hydrocotyle away; because Hydrocotyle will move along meandering water flow through Typha stands and readily establish; reduction of Typha stands is necessary to access and control Hydrocotyle at several locations.

Chemical methods

Discussions centred on: (a) Is Metsulfuron the way forward? Does it have aquatic registration? Application rate? When should it be applied? What frequency? For how long? b) What about Round-up Biactive ? Other aquatic herbicides? (c) Typha reduction with herbicides? (c) Will there be resistance development due to herbicides?

• Some stakeholders expressed the opinion that herbicides should not be used, although the majority of stakeholders were of the view that herbicides are an essential part of eradication efforts. The consensus was that over-use of any herbicide should be avoided and the amounts used minimised.

• SERCUL pointed out the advantages of using the reduced, quarter rate of Metsulfuron (i.e. higher degree of selectivity; less herbicide load); the standard rate of Metsulfuron was acknowledged as providing a comprehensive kill.

• GHD pointed out that ‘in’ and ‘over’ water Round-up Biactive is registered, but Metsulfuron is not (discussions with US experts indicated that Metsulfuron has not been registered for aquatic use because of a less favourable environmental profile compared with Glyphosate; and onerous registration requirements in most countries). However, it can be used in WA under the existing WA Permit 1333.

• GHD also pointed out that where selectivity is not an issue, it is much better to use Round-up Biactive®, which will achieve a comparable and comprehensive kill of even dense Hydrocotyle stands. Glyphosate will also allow Typha to be opportunistically reduced at some locations (i.e. within Wilson Wetlands).


Table 12 (cont.) Summary of Discussions with Stakeholders at Workshops

Issue Discussion notes

Integrated methods

Discussions centred on whether manual methods and herbicides could work together and what might be the ‘order’ of integrating the available methods.

• The ineffectiveness of manual removal was emphasised by SERCUL: (a) manual removal cannot achieve the eradication goal; (b) cannot fully remove roots and stolons; (b) cannot be fully implemented within the lagoons and wetlands, due to in-accessibility and safety issues.

• Herbicides are an essential part of eradication efforts; over-use was not favoured.

• Surfactants are needed; only eco-friendly ones (i.e. vegetable oil or similar) should be used; not ‘Pulse’ penetrant (which is recommended only for terrestrial weed control)

• On the issue of a ‘collaborative’ approach that could be leveraged upon – the consensus was this exists through the Hydrocotyle Working Group, which was endorsed as the facilitator of implementing the Hydrocotyle WMP.

• On ‘integration’ the consensus was as considered in the light of having a ‘Program’ in place instead of a ‘Ad-hoc’ approach;

Specific WMP Elements

Legislative situation: appears to be adequately covered in WA, although GHD pointed out a higher level classification will be beneficial.

Site-specific management zones: different zones will have to be managed with different combinations of methods.

Coordination: Already existing; Hydrocotyle WMP is to be co-ordinated by the Hydrocotyle Working Group with all participant stakeholders;

Public awareness campaigns: Already existing programs in several jurisdictions; need to be co-ordinated by the Hydrocotyle Working Group; cannot reduce the effort on continuing campaign; not just Hydrocotyle, but on other aquatic species also; target aquarium industry.

Community involvement: Already existing programs; need to continue and expand to have other groups be involved; critical to have community support for future funding and implementation of river health programs.

Monitoring & Review of Hydrocotyle Management Plan: Frequency and method to be suggested by Hydrocotyle WMP and implemented by Hydrocotyle Working Group.


Appendix C - Overview of A Weed Management Plan

General Management Philosophy

Weed management is often a part of an overall management of a site, and restoration programs. In general, this requires focusing on the species and communities that are desired to be in place of the weed species in question, rather than on simply eliminating weeds. It is also important to undertake preventative programs to keep the sites free of species that are not yet established there, but are known to be problematic elsewhere in the region.

In setting priorities, it is important to take effective control action to eliminate the target weed established on the site; however, priorities need to be assigned according to their actual and potential impacts on native species and communities, particularly on conservation targets.

Weed management action is justified only when careful consideration indicates leaving the weed unchecked will result in more damage than controlling it with available methods. Weed management benefits from an adaptive management strategy, which has the following steps:

First - establishment of the goals for a site/region;

Second - identifying the species that would interfere with the reaching of these goals; and assigning them priorities, based on the severity of their impacts;

Third - consider methods for controlling the weed(s); or otherwise, reducing their impacts and, if necessary, re-order priorities, based on likely impacts on target and non-target species and on conservation values;

Fourth - develop weed control plans, based on all available information;

Fifth - implement the plan, and monitor the results of management actions;

Sixth - evaluate the effectiveness of our methods in light of the site goals, and use this information to modify and improve control priorities, methods and plans.

Finally, start the cycle again by establishing new/modified goals.

Acting to prevent new infestations and assigning the highest priority to existing infestations that are the fastest growing, most disruptive, and likely to affect the most highly valued area(s) in the region, or a particular site is important. It is also important to consider the difficulty of control, giving higher priority to infestations that are most likely to be readily controlled with available technology and resources.

Setting Priorities

The priority-setting process can be difficult, partly because one needs to consider so many factors. Grouping these factors into categories as given below helps in assigning priorities:

1. Current extent of the species at or near a given site;

2. Potential to spread from that locality to other areas; this is greatly influenced by the size and the vehicles of spread operating at the site; greater the infestation greater the chances of spread; and;

3. Current and potential impacts of the species on conservation, environmental and social Value of the habitats/areas that the species infests or may infest; and

4. Difficulty of control.


The categories can be used in any order, however, the emphasis should be on the importance of the current extent of the species and risk of further spread categories. This is because, in the long run, it is usually most efficient to devote resources to preventing new problems and immediately addressing incipient infestations. Important considerations are:

Value of the habitats/areas the species infests or could infest: Assign priorities in the following order:

– 1. Infestations that occur in the most highly valued habitats or areas of the site - especially areas that contain rare or highly valued species or communities and areas that provide vital resources.

– 2. Infestations that occur in less highly valued portions of the site. Areas already badly infested with other weeds may be given low priority unless the species in question will make the situation significantly worse.

Difficulty of control and establishing replacement species: Assign priorities in the following order:

– 1. Species likely to be controlled or eliminated with available technology and resources and which desirable native species will replace with little further input.

– 2. Species likely be controlled but will not be replaced by desirable natives without an active restoration program requiring substantial resources.

– 3. Species difficult to control with available technology and resources and/or whose control will likely result in substantial damage to other, desirable species.

– 4. Species unlikely to be controlled with available technology and resources.

Weed species whose populations are decreasing and/or those that colonise only disturbed areas and do not move into undisturbed habitats; or impact the recovery from disturbances are assigned the lowest priorities.

Other aspects covered by a WMP are:

1. Weed Management Plan Implementation Schedule

2. Projected Resource Costs to Implement Weed Management Plan

3. Specific Control Plans for Management Units – includes documenting the current distribution of the weed at the site; clarifying Goals

(For example - Outline long-term goals for Hydrocotyle at the Site. For example, the community may want to reduce the levels of infestations of this species, so that it no longer threatens the aquatic environment on the site).

4. Establish Objectives (Measurable) for the planned control activities. Include:

1. The impact on level of abundance (density, cover, etc.) that is proposed to be achieved;

2. The size of the area in which this is proposed to be achieved;

3. The period in which this is proposed to be achieved.

For example, a Site-specific WMP may state the objectives in terms of reducing percent cover of the species by 90% over an area of X acres within 12-months. Another possible objective would be eliminating the species from the site within 2 years).


5. Management Options

Discuss the management options and alternatives; indicate which are preferred and the conditions (size of area treated, location, and phenology, total anticipated cost, etc.) under which they may be used. Build in restricted flexibility to allow those carrying out the plan options; conditions in the field may differ from those you anticipated.

6. Actions Planned (Treatments and monitoring)

Briefly describe the locations to be treated, materials and methods to be used, and an approximate schedule for control and monitoring activities. If several methods are to be tested, outline the design of the planned experiment or demonstration.)

7. How Actions will be evaluated (Criteria for success)

Outline of the methods that will be used to monitor control activities and the criteria that will be used to evaluate success or failure of the program. The criteria for success should be based on the program's objectives and goals.

8. Resources Needs

Estimate the amount of time [for staff, interns and volunteers] and money that will be required to carry out the planned control, monitoring and evaluation for this species.)

9. Results and Evaluation

Results and evaluation should be part of implementing a WMP, to be undertaken preferably within 3 month periods (quarterly) and more comprehensively, at the end of a year, when monitoring data has been taken and evaluated. The evaluation should be used to determine whether any of the actions planned should be modified.)

10. References - List references cited or used.

11. Appendices – the Hydrocotyle WMP may use Appendices that provide the following:

Blank Maps/sample Maps of the site, and of (overlaid) maps depicting the extent of the target weed(s) on the site)

Forms to be used to collect Monitoring Data

Herbicide Use Protocols

Herbicide Use Record Forms

Herbicide Labels and MSDS Sheets


Appendix D – An Update on Hydrocotyle Management at Wilson Wetlands

Background7

The Wilson Wetlands Action Group (WWAG), formed in 1998, has been very active since that time, working on restoring the Wilson Wetlands’ (a brackish water lagoon) environment and maintaining a healthy wetland system. The Wilson Wetlands are part of the Canning River Regional Park. The group has worked to restore the wetlands' fringing vegetation from a weed-infested area into a place where indigenous plants are beginning to expand their range through natural processes (WAGG, 2015a).

The volunteers work on the site at least once per month, during a weekend morning (usually Sunday), conducting weeding, planting and carrying out maintenance tasks. Planting events are also organised each year to involve local school children in valuing the environment.

WWAG has been successful in attracting and managing grants from the Swan Alcoa Landcare Program, Department of Environment and Conservation, and the City of Canning. This has enabled the Group to engage contractors to do additional work that is beyond the scope or qualifications of volunteers, such as herbicide application, and to buy equipment and tools.

WWAG maintains strong working relationships with stakeholders, such as Department of Parks & Wildlife, Swan River Trust, as well as with neighbouring community groups (such as Canning River Volunteers and SERCUL), local schools and individuals. Parts of the Regional Park land WWAG volunteers work on are privately owned by the Trustees of the Christian Brothers (Castledare), who have been supportive of the Group’s commitments and efforts.

Objectives of the Wilson Wetlands Action Group

The primary objective of WWAG is to conserve Wilson Wetlands within the boundaries of the Canning River Regional Park, now and for future generations. WWAG's area of interest is the area within the Canning River Regional Park bounded by Bow Street to the City of Canning Depot, and between the Canning River and Fern Road, Wilson, and the area known as Lot 4 and Lot 501 Fern Road, Wilson (see Map in Figure 7).

As indicated by the WWAG’s Website (WWAG, 2015a), specifically, the actions taken by the Group with regard to the Wilson Wetlands include the following:

a. Prevent fragmentation of the Canning River Regional Park and maintain a buffer zone;

b. Work with relevant agencies to ensure the protection of existing native flora and fauna;

c. Ensure conservation of biological diversity;

d. Work with stakeholders to ensure the conservation of the recreational values of the area known as Lot 4 and Lot 501 Fern Road, Wilson;

e. Revegetate the area with vegetation that is locally indigenous to this region;

f. Establish WWAG's area of interest as an educational resource;

g. Rehabilitate the drains to improve biodiversity and habitat: Mills Street Main drain and Wilson Main drain;

7 Source: http://www.bushlandperth.org.au/member-groups/4-south-of-the-river/80-wilson-wetlands-action-group- and based on consultations with Russell Gorton, Chairperson, WWAG




h. Encourage relevant agencies to provide adequate parking and ablution facilities, with disabled access, at the site of Lot 4 and Lot 501; and

i. Encourage retention and restoration of heritage buildings, structures and vistas.

Synthesis of recent Management Action

WWAG is a member of the Hydrocotyle Working Group and is currently funded by State NRM for work to be undertaken to control the declared weed, Hydrocotyle in the Wilson Wetlands. As part of developing the currently-funded project, WWAG has collaborated and consulted with the following stakeholders:

City of Canning Council;

Department of Parks and Wildlife (DPaW);

Swan River Trust;

South West Aboriginal Land and Sea Council (SWALASC)

State Natural Resource Office. (State NRM office);

South East Regional Centre for Urban Landcare. (SERCUL);

Hydrocotyle Working Group. (HWG); and

The Trustees of the Christian Brothers

Wilson Lagoon (1) is a freshwater wetland in the Canning River Regional Park, which provides nesting, roosting and habitat for native fauna. Regular bird counts, provided by the Canning River Regional Park Volunteers, show approximately 50 bird species, including many species of water birds, occupy the Wetlands.

Observations of the oblong turtle and many nesting sites on the lagoons banks are confirmed, with juvenile turtles also being observed shortly after hatching, making their way back to the wetlands edge. In addition, there are various other native, aquatic species, which occupy aquatic habitat provided by the Wilson Lagoons.

A major threat to the lagoon is the continued reinfestation of Hydrocotyle. If left unchecked, Hydrocotyle aggressively spreads across the surface of the lagoon, growing out from beneath the fringing vegetation and the underlying tree-scape of the Melaleuca rhaphiophylla.

Previous observation and experience has seen this rapidly growing weed requiring ongoing management. It is known that without active management, Hydrocotyle poses a major threat to the conservation values of the Wetlands, which include:

Habitat loss, due to encroachment and displacement of native species;

Poor water quality that may result from dead and decaying vegetation and re-release of nutrients;

Impacts that may result from management action - if Hydrocotyle becomes deeply-entrenched in the Lagoon; for instance, if Hydrocotyle infestations become unmanageable by other means, large amounts of herbicides will be required to control the weed, and this may result in undesirable non-target effects (such as poor water quality with decaying vegetation re-releasing stored nutrients; and off target damage to native sedges and native flora.

9

8

7

6

54

3

2

1 11

10


398,000

398,000

6,457,

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Figure 7


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G:\23\15602\GIS\Maps\Working\2315602_Z010_Hydrocotyle_GHD_2015_A4_Fig7.mxd


0 30 60 90 12015

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LEGEND


Date 02 Sep 2015

Perth Region NRMHydrocotyle Management Plan

Wilson WetlandsGHD Survey July 2015

Data source: WAAG, Monitoring Locations/, 7/8/2015; ESRI, World Imagery/http://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer accessed 7/8/2015 Created by:atdickson


Paper Size A4

DRAFTWilson 1

(Freshwater)

Wilson 2(Saline)

GroundwaterSaline

Discharge

Small SalineWetland

No Hydrocotyle

Small WetlandNo Hydrocotyle

Wilson 3(Saline)

No Hydrocotyle

Mill Street Drain

Inflow fromMill Street

Drain

Wilson Main Drain No

Hydrocotyle

Tidal Movement

PointSource

Location of monitoring points and additional information depicited inannotations provided by Wilson Wetlands Action Group (WWAG)

!( Monitoring Points


Figure 8 An aerial image showing Hydrocotyle infestations on the lower section of Wilson 2 Wetlands

Source Google Earth (2 Sep 2015)


Primary Goals of the Wilson Wetlands Hydrocotyle Management Project

The overall aim of WWAG’s approach is to successfully integrate methods that would reduce herbicide loads required for Hydrocotyle control within the Wetlands. The combination of an intensive manual removal program, coupled with timely and measured herbicide use, and manipulation of other factors influencing Hydrocotyle growth, aim to reduce the levels of Hydrocotyle infestations and eventually eradicate Hydrocotyle from the Wilson Wetlands 1 and 2 and affected areas in Lot 4 of the Castledare Estate.

WWAG is of the opinion that more field research is needed to understand the ecology of Hydrocotyle and its interactions with environmental factors, such as shade, nutrient-rich sediments, water levels and flows and natural inhibitors. These are elements of ‘site-specific’ management, which would prove useful in future management.

Hypothesis: WWAG’s hypothesis is that the growth of Hydrocotyle is correlated with the effects of ebb and flow of tidal movements, along with impacts from ground water saline seepages and freshwater inflows through the discharge, located at the confluence in Lot 4 in Wilson 2 at Castledare. Given that Hydrocotyle is inhibited by increased salinity, and controlled completely by high levels of salinity, the aim is to understand how these factors can be manipulated to manage Hydrocotyle in the future, using non-chemical methods as tools.

The results aim to provide recommendations to all stakeholders as to how Hydrocotyle could be managed in the future without herbicides, but by simply making controlled adjustments to the water levels, and potentially adjusting the Wetlands’ freshwater state to a slightly more saline state, in order to facilitate eradication of Hydrocotyle using natural processes.

To achieve the above objective and further investigations of Hydrocotyle and its freshwater habitat and hydrology appear essential. WWAG aims to develop a better understanding of the correlation between saline and tidal inundation and the influences that these daily incursions may have on Hydrocotyle by conducting regular monitoring of water quality, flows and other influences within the Wetlands.

The Wilson Wetlands and the Canning River are fed by traditional drainage channels from both the Mills St Main Drain and the Wilson lagoon (Wilson 1), which is a freshwater body located directly to the East of Lot 4 and Wilson 2 project area (Figure 7). These two main features of fresh water discharge and mix with the saline influences have major impacts on the capacity of Hydrocotyle to maintain its growth patterns.

There is currently a lack of knowledge as to the exact amount of saline waters, the duration and frequency of saline surges, which are present from both river tides and ground water saline seeps located on Lot 4 of the Castledare Estate that affect the growth and retardation of Hydrocotyle. One of the goals of the Project is to analyse data collected from the Wilson Wetland (Wilson 2) in Lot 4 over an extended period and link it with data collected from the Department of Waters, Kent St Weir, lower gauging station KSW downstream site 6160948.

As part of this Project, WWAG aims to purchase and use water quality data logging equipment for efficient and effective data collection (such as the TPS Field Lab 90 FL)9. This water quality data logger units measure Dissolved Oxygen, Conductivity, TDS, pH, mV, Turbidity and Temperature

8 (Source: Department of Water Website -http://kumina.water.wa.gov.au/waterinformation/telem/stage.cfm ) 9 The 90-FLT is complete water quality logger in a single portable unit. It combines Dissolved Oxygen, Conductivity, TDS, pH, mV, Turbidity and Temperature.

http://kumina.water.wa.gov.au/waterinformation/telem/stage.cfm


WWAG aims to couple the water quality data collection with remote time lapse photography through camera logging and or real time Hydrology monitoring linked with data currently available from the Department of Waters Gauging station in the monitoring program.

Collection of reliable scientific data is expected to provide a better understanding of the effect of the Canning River’s tidal waters and the influence of salinity, measured against the discharge of freshwater data, which will also be collected at the confluence at Lot 4 (Wilson 2).

The current project, implemented by WAGG is unique and different, as for the first time in the Wilson Lagoon area. It proposes a combination of management processes to reduce the extent of Hydrocotyle, aiming to eradicate it from the Lagoon permanently, over a number of years (Russel Gorton, WWAG, July 2015, personal communications).

The Hydrocotyle infestation shown in Plate 11 has been controlled by WWAG; in mid-July 2015, none was found at this location, although it is possible that some Hydrocotyle may exist further upstream intermingled with Typha. A large raft of Hydrocotyle formed between the two small islands in Wilson Wetland 2 (Plate 12). This infestation was also controlled and in mid-July 2015, none was found at this location.

Plate 11 Hydrocotyle growing out of Typha infestations (14/2/2012) at Wilson Wetland 2

WWAG continues to liaise with all stakeholders involved with Hydrocotyle management in the Canning Region, and has been undertaking the management of the weed in Wilson Wetlands. Updates on the progress of works have been provided to the Hydrocotyle Working Group.

Plate 12 Hydrocotyle infestations in Wilson Wetland 2 (14 Feb 2015)


WWAG has been trialling integrated techniques: i.e. manual removal techniques, combined with the use of herbicide applications, and also with different types of herbicides, including Metsulfuron-methyl and Bi-active Glyphosate. The work is covered by the APVMA Permit Number PER13333, which allows the use of Metsulfuron to control Hydrocotyle as a declared Environmental weed posing risks to wetlands in WA.

The installation of temporary floating booms with drift skirts (relocatable, reusable floating fencing), aiding in the capture of breakaway pieces of Hydrocotyle and to reduce the incidence of reinfestation in areas that are cleared of Hydrocotyle (Plate 13). These methods are regarded as quite successful in containing the existing infestations.

Plate 13 Hydrocotyle removal by hand by WWAG volunteers at Wilson Wetland 2 (16 April 2015)

Due to the boggy nature of the wetlands and the unstable wetland floor in some areas, a small boat or canoe is expected to provide safe access where necessary. Both manual removal and spot treatments herbicides are planned to be used in managing difficult-to-access infestations.

Planned Outputs and reportable outcomes

As evident from the consultation process with WWAG, the following are reporting outcomes on the objectives and approach that are part of WWAG’s Project for managing Hydrocotyle within the Wilson Wetlands:

Continue to engage with partner agencies, Local Government, community groups and all stakeholders through the Hydrocotyle Working Group;

Continue to manage the established trial plots and monitoring sites and review data whilst trialling new and existing controls and report outcomes to all stakeholders;

Continue the water quality data collection and other monitoring data that would allow an assessment to be made on how the salinity and freshwater influences may be managed to cause a decline of Hydrocotyle infesting the Wetlands;

Continue to map the existing and new populations of Hydrocotyle with GPS and make this information public and available to all stakeholders;

Actively, manually remove and reduce Hydrocotyle populations located in Lot 4 in Wilson 2 and also treat and reduce or remove all other associated weeds/macrophytes with which Hydrocotyle infestations are currently co-existing (i.e. Typha);

Create access to control Hydrocotyle outbreaks, deeply entrenched within the Wetlands 1 and 2 using appropriate methods; this may involve some mechanical methods;


Control Hydrocotyle infestations by combining manual removal and other methods (such as salinity manipulations if possible and fencing), combined with the application of minimal amounts of different herbicides where necessary and appropriate;

In using herbicides for spot treatments, comply with the herbicide labels, MSDS and the off-label permit PER13333 (APVMA); and

Deploy temporary small booms with drift trapping capacity when needed during treatment periods to reduce the incidence of reinfestation in areas cleared of Hydrocotyle.

Update on Control treatments and achievements

WWAG Volunteers have been undertaking Hydrocotyle management in the Wilson Wetlands 1 and 2 since 2014-15. The initial large areas of Hydrocotyle infestation have declined within a short space of time with no herbicide treatment, and the current infestations, localised only in some small sections are starting to build biomass and newsstands of weed infestations.

The volunteers undertook the first treatment of hand removal of trial Plot 2 on 16 April 2015 (see Plate 13). Results of the hand removal indicated almost nil Hydrocotyle in this plot and no further follow-up treatments appear to be necessary (as at end of July 2015).

However, Trial Plot 2 may also need a spot treatment of herbicide, to kill off the Hydrocotyle, which is embedded in the built-up sediments around the basal areas of the Melaleuca trees. WWAG would seek advice on the best herbicide to use for this purpose.

Some water quality data obtained in July are provided in Table 13 as a snapshot. The data indicate the levels of salinity at various locations. Continuous data collection may clarify the interaction between the freshwater discharges at Site 10 and other areas and how these may be manipulated to create unfavourable conditions for Hydrocotyle.


Table 13 Some monitoring data from Wilson Wetlands Water Quality Monitoring

site number

time sampled pH EC -

mS/cm EC -

µS/cm Turbidity

NTU daily

weather observations and location Temp 0C

depth of sample mm

tidal movements

1 8.00 am 7.1 1.1 1100 <9 overcast Sample above Railway bridge 13.5 300 falling

2 8.09 am 7.4 2.1 2100 <9 overcast Saline seep at Fern Road 14.5 200 due to shallow nature of the seep falling

3 8.20 am 7.5 0.6 600 <9 overcast Out fall of Mills St Main Drain 14.5 300 falling

4 8.27 am 7.4 0.8 800 <10 overcast North eastern corner of Wilson 1 13.5 150 due to shallow nature of wetland falling

5 8.35 am 7.4 0.8 800 <10 overcast Drain out fall eastern end of Wilson 1 14.5 400 falling

6 9.20 am 7.8 0.6 600 <10 overcast Sample next to trial plot 1 Control 13.5 200 due to sediment

disturbance falling

7 9.30 am 7.5 0.8 800 <10 overcast Next to old pipe sticking out of the embankment 13.8 300 falling

8 9.38 am 7.4 0.7 700 <10 overcast Sample below Hydrocotyle trap 13.8 300 falling

9 9.42 am 7.5 2.2 2200 <10 overcast Sample in middle of Wilson 2 13.8 300 falling

10 10.00 am 7.5 0.5 500 <10 overcast Sample at freshwater discharge from Wilson 1 into Wilson 2 13.8 300 falling

11 10.09 am 7.5 3.6 3600 <10 overcast Sampled in Canning River adjacent to Gauging station 13.8 400 falling

Note: Conductivity in Freshwater: 30 – 2000 µS/cm; brackish water: > 2000 µS/cm


Appendix E – Minimising Potential Impacts of Herbicide Use

Source: Department of Agriculture and Food - https://www.agric.wa.gov.au/pests-weeds-diseases/control-methods/chemicals/herbicides

Herbicide treatment of weeds should be used as part of an integrated weed management approach. Non-chemical methods may successfully deal with a number of weed species, but there may also be species that are best controlled with the use of herbicide. These usually include rhizomatous species such as Kikuyu, Couch and Nutgrass.

It may also be better to spray large infestations of difficult to remove weeds such as Blackberry and Arum Lily, and to stem inject or paint the cut stems of large woody weeds, such as Japanese Pepper. Initial treatment with herbicide may be supplemented with other methods, such as hand removal in the follow-up treatment.

It is important that herbicide use is as effective as possible, reducing the volume of herbicide used and the number of applications required. The following principles are designed to reduce the risks of herbicide use through minimising the amount applied, maximising the death of weed populations, and careful timing of herbicide application.

Apply herbicide according to the recommended rate.

If possible, try to spray when surface water levels are low, generally in early winter after germination has occurred, but stream levels have not risen appreciably.

Ensure that weeds are sprayed at the correct time, usually when they are growing strongly, and before seed set.

Minimise damage to frogs by determining the species present, and ensuring that as far as possible herbicide is not applied during egg laying, tadpole development or at the point where the juvenile frogs emerge from the water.

Mix in a coloured dye so that you can accurately see which areas have been sprayed, and whether areas have been missed.

Ensure adequate follow-up of weed treatment, so that repeat treatment is minimised.

Other information on Herbicide Use in Waterways is also available and should be included in the training of personnel for implementing the Hydrocotyle WMP. For instance, the Cooperative Research Centre (CRC) for Australian Weed Management produced guidelines for the use of herbicides in and around water (CRC, 2005). The Guidelines state as follows:

“…The use of herbicides near waterways should be minimised, and therefore, it is important to consider other techniques that can be alternatives to, or complementary with, herbicides. These other methods include mechanical removal, mulch or weed mat, shading, fire, flame guns, biological control agents, manual control, slashing, ring-barking and controlled grazing. Developing an integrated approach to weed management, combining all appropriate weed control options into an integrated weed management (IWM) plan is the most desirable way to combat weeds. The IWM plan will be different for each site, according to the characteristics of the riparian area and the weed(s) present...”

The Guidelines provide detailed advice on undertaking additional risk assessments for non-target effects of registered aquatic herbicides

https://www.agric.wa.gov.au/pests-weeds-diseases/control-methods/chemicals/herbicides

https://www.agric.wa.gov.au/pests-weeds-diseases/control-methods/chemicals/herbicides


GHD

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This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorised use of this document in any form whatsoever is prohibited. G:\23\15602\WP\Final WMP Reports\210104_NC_CF_Final V1 (16 Dec 2015) with NEW REVISIONS 2 GG edits NC Revised.docx

Document Status

Rev No.

Author Reviewer Approved for Issue Name Signature Name Signature Date

Draft Nimal Chandrasena

Christobel Ferguson

Christobel Ferguson

1 Sep 15

Rev 1 Nimal Chandrasena

Minor revisions

9 Oct 2015


Minor revisions

16 Dec 2015


Minor revisions

20 Jan 2016


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