Evaluation of Herbicide Applications for Control of ...invasives.glifwc.org/apm.workshop/pdf/apm...

Evaluation of Herbicide Applications for Control of Aquatic Invasive Species

Michelle NaultWDNR Research

John SkogerboeU.S. Army Corps of Engineers

APM in the Ceded TerritoryLCO Convention Center

December 5, 2012

EWM Distribution

CLP Distribution

Research Questions About EWM & CLP

1) Ecology-What are the possible outcomes when EWM or CLP is introduced to a lake?

-What factors contribute to different outcomes?-Interannual variation?

2) Management-Past management (non-strategic) = short term nuisance relief?

-Future management (strategic) = long term reduction and restoration?

Implementation Considerations

• Management tool(s)• Management goal(s)• Timing (seasonality, weather, water temps)• Herbicide products and formulations• Application rates• Flowing water, water level management• Lake type, size, bathymetry, water chemistry• Target and non-target plant species

NR 107 Aquatic Plant Management –Chemical Use.

“NR 107.01. Purpose. The purpose of this chapter is to establish procedures for the management of aquatic plants and control of other aquatic organisms pursuant to s. 227.11 (2) (a), Stats., and interpreting s. 281.17 (2), Stats. A balanced aquatic plant community is recognized to be a vital and necessary component of a healthy aquatic ecosystem. The department may allow the management of nuisance-causing aquatic plants with chemicals registered and labeled by the U.S. environmental protection agency and labeled and registered by firms licensed as pesticide manufacturers and labelers with the Wisconsin department of agriculture, trade, and consumer protection. Chemical management shall be allowed in a manner consistent with sound ecosystem management and shall minimize the loss of ecological values in the water body.”

Engineer Research and Development CenterUS Army Corpsof Engineers

Objectives of Invasive Aquatic Plant Management Using Herbicides

1. Efficacy: Control invasive exotic aquatic plants

2. Selectivity: Minimize adverse impacts to native plants, protect native aquatic plants from invasives


US EPA

University of Florida,Center for Aquatic &

Invasive Species

US Army Engineer Research and Development

Center

Lewisville Aquatic Ecosystem

Research Facility

Eau Galle Aquatic Ecosystem

Research Facility

US Army Engineer Research and Development Center (ERDC)


Research Partners


Primary Invasive Species and Aquatic Herbicides

Eurasian Watermilfoil & Hybrid milfoil

1. 2,4-D

2. Endothall

3. Triclopyr

4. Fluridone

5. Diquat

Curly-leaf pondweed

1. Endothall

2. Fluridone

3. Diquat


Indoor Growth Chambers and GreenhouseGrowth Chambers, Vicksburg, MS

Greenhouse,Lewisville, TX

• Wide range of herbicide conc. and exposure times

•Replicated studies

•Temperature

•Light intensity and duration

•Water quality

Environmentally Controlled


Outdoor Mesocosms

•30, 7000 L tanks

•Flow rate controls

24, 1100 L shallow tanks


Eurasian Watermilfoil Efficacy2,4-D Concentration/Exposure Time Relationship

J. Aquat. Plant Manage 30: 1-5


Concentration/Exposure Time RelationshipEndothall (Aquathol K)


•Degradation vs dissipation

•Project scale


Herbicide Selectivity

> 85% Control

Eurasian watermilfoil

American elodea



Herbicide Selectivity

•Concentration, Exposure Time

•Species sensitivity


Minimum Exposure Time Requirements for Eurasian Watermilfoil Control

• 2,4-D: > 18 hours• Endothall: > 18 hours• Triclopyr: > 18 hours• Fluridone: > 60 days• Diquat: > 1 hour


Herbicide Treatment Categories

• Whole Lake Treatments

• Spot Treatments

• Micro Spot Treatments (< 5 acres ?)

• Flowages (Mohawksin, WI) and Complex Mega Lakes (Lake Minnetonka, MN)

Herbicide Monitoring Project Lakes•Legend, Menominee•Connors, Sawyer•Lower Spring, Jefferson•Kathan, Oneida•Enterprise, Langlade•English, Manitowoc•Forest, Fond du Lac•Wilson, Price•Antigo, Langlade•Washington, Shawano

•Monona (Turville), Dane•Tomahawk/Sandbar, Bayfield•Eagle, Racine•Half Moon, Eau Claire•Loon, Shawano•Big Sand, Vilas•Long, Vilas•South Twin, Vilas•North Twin, Vilas•Little St. Germain, Vilas•Eagle River Chain, Vilas•Frog, Florence•Jordan, Adams•Kettle Moraine, Fond du Lac•Metonga, Forest•Minocqua, Oneida•Kawaquesaga, Oneida•Tomahawk, Oneida•Bridge, Oneida/Lincoln •Mohawksin, Lincoln

•Tomahawk/Sandbar, Bayfield Co.•South Twin, Vilas Co.•Forest, Fond du Lac Co.

•Connors, Sawyer Co.•Little St. Germain, Vilas Co.

Small

Scale

Whole

Lake

Whole Lake Small Scale

Case Studies

•Wilson Lake, Price Co.Flowage

Flowage

2,4-D Concentration/Exposure Time

Green & Westerdahl, 1990JAPM 28:27-32

Recommended label rate: 2.0 – 4.0 ppm

ppm

ae

2.0

0.5

1.5

1.0

(Hours) 1.0 ppm = 1.0 mg/L = 1000 ppb

‘High’ doseShort exposure

‘Low’ doseLong exposure

Herbicide Exposure Time

• Dissipation– Water flow– Wind– Treatment area relative to lake– Water depth

• Degradation– Microbial– Photolytic

Application Timing/PhenologyEarly Spring Herbicide Applications

•Exotic species are small and most vulnerable

•Many native species are dormant

•Cool water temperatures result in slower microbial degradation

•Minimize biomass decomposition

Herbicide Water Sample Collection

Immunoassay Test (ELISA)

Aquatic Plant Surveys – Hauxwell et. al 2010

Survey Methods




mg/

L ae

2.0

0.5

1.5

1.0

Whole Lake Treatments

(Hours) 1.0 mg/L = 1.0 ppm = 1000 ppb

1) What are the effects of early season 2,4-D on Eurasian watermilfoil?

2) What about native plants?

Approach: Monitor annual changesin plant communities in experimental lakes (herbicide or reference)

Sandbar/TomahawkWDNR, Army Corps of Engineers, Town of Barnes,

Bayfield County

No Treatment

2,4-D Treatment

Study design

• Low dose liquid 2,4-D (0.5 ppm) treatment to whole lake (May 20, 2008)

• Aquatic plant surveys conducted 2006-2012

• Biomass collected during 2007-2012 surveys

• Reference lake – no treatment (2007 - 2010)

• Low dose liquid 2,4-D (0.275 ppm) treatment to whole lake epilimnion(spring 2011)

• Aquatic plant surveys and biomass collected during 2007-2012

Tomahawk Sandbar

Tomahawk vs. Sandbar, Bayfield Co.July 2007 Summary Stats

Tomahawk Sandbar

Lake size (ha) 53.1 51.3

Maximum depth (m) 12.8 14.9

Maximum depth of plant colonization (m)

6.8 7.0

Percentage of littoral zone vegetated 86.4 86.8

Number of species 20 17

Mean number of species per site (littoral)

2.6 2.8

Simpson’s Diversity Index 0.90 0.89

Eurasian watermilfoil frequency of occurrence within littoral zone (%)

39.9 25.8

Tomahawk Lake, Bayfield Co.2006 - 2012 Summary Stats

0

10

20

30

40

% F

requ

ency

of O

ccur

renc

es (L

ittor

al)

Species

Tomahawk Lake, Bayfield Co.Species % Frequency of Occurrences

2006200720082009201020112012

* = p ≤ 0.05** = p ≤ 0.01

*** = p ≤ 0.001

*

***

***

******

***

***

***

****

**** *

***

**

*****

***

*

**

*

*

**

***

*

Herbicide Sample Locations

Collected pre-, 1, 2, 3, 5, 7, 14, 21, 28, 35, 42, 49, 56+ days after treatment

Tomahawk 2,4-D Concentrations

0

100

200

300

400

500

600

700

800

900

1000

0 20 40 60 80 100 120 140 160 180

Days after treatment

2,4-

D re

sidu

es, u

g/L

T1T2T3T4T5

Application Rate = 0.5 ppm (500 µg/L)

Sandbar Lake, Bayfield Co.2007 - 2012 Summary Stats

0

10

20

30

40

50

60

% F

requ

ency

of O

ccur

renc

es (L

ittor

al)

Species

Sandbar Lake, Bayfield Co.Species % Frequency of Occurrences

200720082009201020112012

* = p ≤ 0.05** = p ≤ 0.01

*** = p ≤ 0.001

*

***

********

*

***

Sandbar EWM

Sandbar 2,4-D ConcentrationsSandbar Lake 2,4-D Herbicide Concentrations, 2011

Application Rate = 0.275 ppm (275 µg/L)

Stratified Lake

Mixed Lake

Lake Depth Stratification

No TreatmentTomahawk Sandbar 2,4-D

Treatment2,4-D Treatment

Water Quality

1) What are the effects of early season 2,4-D on Eurasian watermilfoil?

2) What about native plants?

Approach: Monitor annual changesin plant communities pre- and post-treatment

South Twin Lake, Vilas Co.WDNR, Army Corps of Engineers, Onterra LLC

2,4-D Treatment

South Twin, Vilas Co.• EWM discovered July 2001

• Spring 2009: Liquid 2,4-D applied to EWM areas at 1.75 ppm (lakewide target = 0.167ppm)

• May 2010: Liquid 2,4-D applied to EWM areas at 2.5 ppm (lakewide target = 0.24 ppm)

• Pre- and post-treatment aquatic plant surveys 2008-2011 by Onterra LLC

SOUTH TWIN, VILAS

Lake size (acres) 627.71Max depth (ft) 43

Avg depth 20Lake type Drainage

South Twin Lake, 2010 2,4-D Herbicide Residuals

0

500

1000

1500

2000

2500

0 7 14 21 28 35 42


Con

cent

ratio

n (µ

g/L

ae)

Mean TreatedMean UntreatedLakewide TargetIrrigation Limit

Lakewide DissipationSouth Twin Lake, 2010

2,4-D Herbicide Concentrations2.5

2.0

1.5

1.0

0.5

0

Con

cent

ratio

n (p

pm)

South Twin – Chi Square

Forest Lake, Fond du Lac Co.• EWM first discovered 1992 • DNA analysis confirmed as

M. spicatum X M. sibiricum• Liquid 2,4-D applied to five

sites at 0.6 ppm on May 18, 2011

• Whole-lake target = 0.305 ppm• Lake volume factored in

stratification at ~15 feet• EWM surveys pre- and post-

treatment by Onterra LLC

FOREST, FOND DU LAC

Lake size (acres) 51

Max depth (ft) 32

Avg depth 11

Lake type Seepage

Forest 2,4–D ConcentrationsForest Lake 2011, 2,4-D Herbicide Concentrations, <10 feet deep

Forest Lake 2,4-D Herbicide Residuals

0

50

100

150

200

250

300

350

0 7 14 21 28 35


Con

cent

ratio

n (µ

g/L

ae)

5 ft10 ft15 ft20 ft25 ftTarget Conc.

Lake Stratification

Forest Lake, 2,4-D Herbicide Concentrations

Forest LakeHybrid EWM Spring 2011

Legend

EWM Rake Fullness = 1!(



73%

23%

4%

Spring 2011Courtesy of Onterra

Forest LakeHybrid EWM Summer 2011

Legend




89%

10%

1%

Summer 2011Courtesy of Onterra

Wilson Lake, Price Co.• EWM first discovered August

2002 • Spring 2012: Liquid 2,4-D

applied to three sites at 1.0-1.7 ppm

• Whole-lake target = 0.331 ppm• Aquatic plant surveys pre- and

post-treatment by Onterra LLC• Herbicide concentration data

collected within and outside treatment areas

WILSON, PRICE

Lake size (acres) 348

Max depth (ft) 11

Avg depth 6

Lake type Drainage

Wilson Lake, Price Co.

Wilson Lake, Price Co.Statistically Valid p-value

Myriophyllum spicatum Eurasian w ater milfoil 11.7 0.0 -100.0 ▼ Yes 0.000Ceratophyllum demersum Coontail 44.4 9.7 -78.2 ▼ Yes 0.000Nymphaea odorata White w ater lily 9.2 9.7 5.6 ▲ No 0.863Nuphar variegata Spatterdock 2.6 2.0 -20.0 ▼ No 0.736Brasenia schreberi Watershield 1.0 0.5 -50.0 ▼ No 0.562Myriophyllum sibiricum Northern w ater milfoil 0.5 0.0 -100.0 ▼ No 0.317Utricularia vulgaris Common bladderw ort 0.0 0.5 100.0 ▲ No 0.317Potamogeton robbinsii Fern pondw eed 33.7 14.3 -57.6 ▼ Yes 0.000Potamogeton zosteriformis Flat-stem pondw eed 12.2 1.0 -91.7 ▼ Yes 0.000Potamogeton pusillus Small pondw eed 5.6 0.5 -90.9 ▼ Yes 0.003Chara spp. Muskgrasses 3.1 0.0 -100.0 ▼ Yes 0.014Najas flexilis Slender naiad 3.1 0.0 -100.0 ▼ Yes 0.014Vallisneria americana Wild celery 2.0 0.0 -100.0 ▼ Yes 0.044Elodea canadensis Common w aterw eed 9.2 4.6 -50.0 ▼ No 0.073Potamogeton amplifolius Large-leaf pondw eed 4.6 7.7 66.7 ▲ No 0.206Nitella spp. Stonew orts 4.1 6.1 50.0 ▲ No 0.359Lemna trisulca Forked duckw eed 3.1 0.5 -83.3 ▼ No 0.057Potamogeton epihydrus Ribbon-leaf pondw eed 2.6 0.5 -80.0 ▼ No 0.100Spirodela polyrhiza Greater duckw eed 2.0 0.5 -75.0 ▼ No 0.177Potamogeton natans Floating-leaf pondw eed 1.5 2.0 33.3 ▲ No 0.703Eleocharis palustris Creeping spikerush 1.0 0.0 -100.0 ▼ No 0.156Eleocharis acicularis Needle spikerush 0.5 0.0 -100.0 ▼ No 0.317Potamogeton spirillus Spiral-fruited pondw eed 0.5 0.0 -100.0 ▼ No 0.317Sagitaria sp. (rosette) Arrow head rosette 0.5 0.0 -100.0 ▼ No 0.317Sagittaria rigida Stiff arrow head 0.5 0.0 -100.0 ▼ No 0.317Typha spp. Cattail spp. 0.5 0.0 -100.0 ▼ No 0.317Lemna turionifera Turion duckw eed 0.0 1.0 100.0 ▲ No 0.156Schoenoplectus acutus Hardstem bulrush 0.0 0.5 100.0 ▲ No 0.317Sparganium emersum Short-stemmed bur-reed 0.0 0.5 100.0 ▲ No 0.317

2011 & 2012 N = 196LFOO = Littoral Frequency of Occurrence▲ or ▼ = Change Statistically Valid (Chi-square; α = 0.05)▲ or ▼ = Change Not Statistically Valid (Chi-square; α = 0.05)

Chi-square AnalysisScientific Name Common Name

Dic

ots

Non

-dic

ots

2011 LFOO 2012 LFOOPercentChange Direction

EWM Control

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Mean 2,4-D Concentration 0-7 DAT (ppm)

EWM Control

High level of control

Damage to natives

No control

Seasonal control

Damage to some natives

???

Focus area

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Mean 2,4-D Concentration 0-7 DAT (ppm)

Native Species

Preliminary Findings• Recommended label concentrations may not be

applicable for whole lake or large scale treatments • Herbicide dissipation is rapid and large scale treatments

can result in a whole-lake treatment if the scale of the treatment area is large compared to the overall lake volume

• Lake stratification and water temperature are important to consider when calculating volume

• Early spring, large scale treatments may result in longer persistence of herbicides than expected; may exceed 100 ppb (0.1 ppm) for >21 days

• EWM control looks promising, however short-term damage to certain native species may occur and long term effects on biotic and abiotic parameters is uncertain

• Hybrid watermilfoils need to be better documented and studied in both field and laboratory studies

• Herbicide monitoring is important, both to understand treatment efficacy, as well as ecological risks




ppm

2.0

0.5

1.5

1.0

(Hours)

Small scale Treatments

1.0 ppm = 1.0 mg/L = 1000 ppb

Connors – Treatment Map

Connors – 2,4-D ConcentrationConnors Lake, Sawyer Co.

2,4-D Herbicide Residuals 2010

0

200

400

600

800

1000

1200

0 24 48 72 96 120 144 168

Hours After Treatment (HAT)

Con

cent

ratio

n (µ

g/L

ae)

C-1C-2C-3C-4Irrigation Standard

Connors Lake, Sawyer Co.

2,4-D Herbicide Concentrations 2010

Area vs. Concentration 24 HAT

Connors Lake, Sawyer Co. 2,4-D Herbicide Residuals 2010

0

500

1000

1500

2000

2500

3000

3500

0 24 48 72


Con

cent

ratio

n (µ

g/L

ae)

Mean Bay Sites (A,D,E)

Mean Exposed Sites (F, G, H, I)

100 µg/L ae



Treatment Site LocationProtected vs. Exposed Sites

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5 10 15 20 25 30 35 40 45

Area (acres)

Mea

n [2

.4-D

] 0-2

4 H

AT

ProtectedExposed

Connors Lake, Sawyer Co. 2,4-D Herbicide Residuals 2010

0

100

200

300

400

500

600

700

0 6 12 18 24


Con

cent

ratio

n (µ

g/L

ae)

Mean BottomMean SurfaceIrrigation Standard



Endothall Treated Area: 35 acPercent treated area: 4% Target Conc. = 1.05 ppm

2,4-D Treated Area: 29.3 ac Percent treated area: 3%Target Conc. = 2.23-2.43 ppm

Little St. Germain, Vilas Co.

Little St Germain Endothall Concentrations, 2011Site CLP B-11(E)

0

200

400

600

800

1000

1200

1400

1600

1800

0 6 12 18 24 30

Hours After Treatment

Endo

thal

l Con

cent

ratio

n, u

g/L

ae

Surface Mean Bottom Mean

Target Concentration Detection Limit

Little St. Germain, Vilas Co. Endothall

Little St Germain 2,4-D Residual Concentrations, 2011Site H-11 (D)

0

50

100

150

200

250

300

0 6 12 18 24 30Hours After Treatment

2,4-

D C

once

ntra

tion,

ug/

L ae

Surface Mean Bottom Mean

Irrigation Std

Little St. Germain, Vilas Co. 2,4-D




mg/

L ae

2.0

0.5

1.5

1.0

(Hours) 1.0 mg/L = 1.0ppm = 1000 ppb

Small scale treatments

Preliminary Findings• Actual CET in the field is more difficult to predict

and maintain in smaller scale treatments• Aquatic plant data is more difficult to collect and

analyze in smaller scale treatments• Rapid dissipation occurred and concentrations

were < 100 ppb (0.1 ppm) by 24 HAT in many treatment sites

• Mean concentrations in the protected sites were greater than those from the more exposed sites

• Granular formulation did result in a vertical gradient from top to bottom, however horizontal dissipation through the water column was rapid and similar to liquid formulations

Wild Rice Selectivity Literature• Nelson, Owens & Getsinger (2003). ACOE ERDC Tech Report.

• Invasion of exotic plants may contribute to the decline and displacement of wild rice

• Controlled tank study examining four herbicides at varying application rates and wild rice growth stages

• Wild rice treated at earlier growth stages (early tillering or seedling) was more sensitive to chemical treatment

• Wild rice treated at the mature growth stage (late tillering and flowering) was not affected

• Endothall, diquat and fluridone reduced dry weight but not seedhead or tiller production

• 2,4-D rates of 1.0 ppm sustained for 7 DAT inhibited production in young wild rice

Wild Rice Selectivity Literature• Madsen et al. (2009). J. Aquatic Plant Mgmt.

• Controlled tank study examining the herbicide triclopyr at

varying application rates and wild rice growth stages

• Wild rice exposed to 0.75 ppm for 72 hours did not reduce

height, biomass, seed density or tiller production

• Wild rice exposed to 2.5 ppm for 72 hours reduced height and

biomass

• Wild rice seedlings exhibited the greatest sensitivity to triclopyr,

while young and mature plants were more tolerant

Next Steps• The WDNR and Army Corps of Engineers have compiled

a draft summary report of the herbicide monitoring project case studies, and will continue with a final synthesis

• Continue evaluation of the longevity of whole lake and large scale treatment impacts as well as native plant and water quality responses

• Continue evaluation and monitoring of the efficacy of small scale treatments utilizing different application techniques and formulations

• Further exploration of hybrid water milfoils and effectiveness of herbicide treatments

• Further exploration of potential direct and indirect impacts on other organisms

Deciding on the best management approach:

1) Quantify the problem – collect data!

2) Set reasonable expectations and goals (ecological and economical)

3) Weigh the benefits with the risks

4) Recognize that managing invasives is a long-term commitment with any tool (action based on data)

DISCUSSION

[email protected]

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