Post on 22-Dec-2015
Pest Control in the OrchardAndrew Hewitt, Director Centre for Pesticide Application and Safety,
University of Queensland, Australia and Research Professor The University of Nebraska, USA; Adjunct Prof., Lincoln University, NZ
Geoff Furness, Mark Ledebuhr, Chris O’Donnell, SARDI, AI, UQ
Thanks To
l Australian industry: Apple and Pear Australia Ltd, AGWA, others
l International: UQ, SARDI, Application Insight, HortResearch, PGG Wrightson and Pipfruit NZ, many others
Black Spot/ Apple Scab
l Fungal spores (e.g. from leaf litter) can cause leaf infection any time from bud break to full bloom. Infection is related to the length of continuous leaf wetness and ambient temperature, from 5 hours above 25°C to 20 hours at 6°C – hence biological prediction based on weather forecasts and irrigation to avoid prolonged contact wetting
l Prevention depends mostly on successful fungicide applications to prevent primary infections in spring
Gloeosporium and other Rots
l Fungal disease typically seen during storagel Cultural control (if practical) involves pruning and removing
cankers during winter, and new cankers on limbs and trunks in spring/ summer as well as 1-year old shoots that wilt or die in spring/ summer. Minimize low hanging fruit late season
l Calcium sprays improve fruit resistancel Chemicals like Captan if rainy periods occur prior to harvest but
not within 7 days of harvest. E.g. 2 applns. of Mizar before its 28-35 day cutoff; then Captan 14 days before harvest; Pristine at 100% bloom/ petal fall (Gary Speers, PGG Wrightson, NZ)
Fungicides
l Protectant before spores land on leaves (use weather forecasts and apply before infection occurs)– e.g. Dodine
Pyrimidines Strobilurins azoxystrobin, fenamidone, kresoxim methyl, fluoxastrobin, pyraclostrobin,
trifloxystrobin Dithiocarbamates metiram, mancozeb, thiram, mizar
l Curative after infection occurs, for up to 5 days post-raine.g. DMI group
Organic Fungicides
l Potassium bicarbamatel Copper or Bordeaux mixture early in season such as
around budburst (limited effectiveness)l Wettable sulfurl Mineral/ neem oilsl Natural phenols/ phytoalexins
Genetic resistance
l Over a dozen genes have been isolated in apple cultivars that offer resistance to fungal diseases
l Just as pests evolve to provide challenges to their control, we can adapt by selecting optimized genetics along with customized pesticide and application systems
Tolerances
l Maximum Residue Levels/ Limits (MRLs) in fruit (and sometimes in pomace)
l Vary according to country of use, e.g.Boscalid 2-3 mg/kgPyraclostrobin 0.5 mg/kgCaptan 3-25 mg/kgDiothiocarbamates 0.5-10 mg/kgDodine 0.9-5 mg/kgStrobilurins 0.1-5 mg/kgPyrimidines, e.g. fenarimol 0.2-1 mg/kg
Apple and Pear AU Website MRL Tablehttp://apal.org.au/wp-content/uploads/2013/04/Apple-and-Pear-MRLs-September-2014.pdf
European Food Safety Authority
l Bases MRLs on properties of the ag product and good ag practices to ensure lowest possible human exposure (Reg EC396/2005)
l Risk assessment based on consumer intake being less than the toxicological ref value for each active
l Annual reporting of residues for >800 pesticides from >60,000 food samples across Europe and >15,000,000 member state measurements
Fungicide Resistance Plans
Sterol inhibitors, pstrobilurins and others affected while contact fungicides are less affected
l Diodine – less than 7 applications per season; less than 4 in sequence
l Pyrimidines – less than 5 applications per seasonl Strobilurins – less than 4 applications per seasonl DMI fungicides – less than 5 applications/
season; always in a cocktail with protectants
Loss of Chemicals other than through Resistance
l De-registration, e.g. Benzimidazole not allowed in many countries due to Benzene content; some adjuvants restricted due to alleged toxicity (this is always a threat, even with the most widely accepted pesticides)
l Risk assessment involves assessing exposure, dose and toxicity – need to address all these to maintain use
l Increasing restrictions on purchasing such as quality assurance schemes, sprayer testing schemes and auditing of produce from the tree to the supermarket shelves
Managing Pesticide Losses
l Many studies in tree crops have shown that more than half the applied chemical can be wasted on the ground and in airborne losses such as drift, rather than staying on the intended canopy
l Application technology, meteorological conditions, canopy and tank mix chemistry are all important
l Increasingly, countries are introducing restrictions on spraying but relaxing them if drift reduction technologies are used (Europe for decades and in 2015 the US, Canada and Australia as well as many others)
Spray fate in Orchards (Giles)
Author Condition Ground Target Drift
Seiber Dormant 25 – 45% - -
Cross Both 43 - 63% - 16%
Vercruysse Both - 56 – 68% -
Pergher In season - 37 – 62% -
Fox “Sparse” 57% - -
Miller In season 22% 57% 4.6 (16%)
Optimized spraying of tree and vine crops
l Consider application rate on a distance/ height basis (e.g. 20-40 L/ 100 m per vertical canopy m)
l Do not spray above canopy top or below lower foliagel Relatively fine sprays are needed for coverage (droplet size can
be a major regulatory issue) + higher volumes than most other crop types and air-assistance is desirable for achieving penetration into the canopy and uniform coverage at all regions
l Calibrate sprayer and assess coverage, e.g. using fluorescent dyes/ UV light illumination looking at all canopy areas. Adjust as needed and repeat
l Spray Volume Calculator (L/100m of row)
l/min 3 km/h 4km/h 5km/h 6km/h 7km/h 8km/h
6 12 9 7.2 6 5.1 4.5
10 20 15 12 10 8.6 7.5
14 28 21 16.8 14 12 10.5
18 36 27 22 18 15 14
22 44 33 26 22 19 17
26 52 39 31 26 22 20
30 60 45 36 30 26 23
Other useful formulae:l Length of row /hectare = 10 000 ÷ row spacing (m)l Number of tanks required =
total row length x spray volume ÷ volume of tank
(m) (litres/100m) (litres)
÷ 100l Litres / hectare = litres / 100 m ÷ row spacing x 100
Sample leaves from all canopy areas and leaf regions
Example of dye on grape leaves but apples would be assessed the same way
Alternative Assessment System using Kromekote and Image Analysis
l Black food dye on Kromekote, 4800 DPI scan, image analysis
What you see (2 centimeter scan) What the computer sees:
Why hi-resolution image analysis?
l Tool to better understand what is going on DEEP in low-coverage areas. Understand and compare the areas of weakest application for better understanding of the overall application.
Typical resolution scan, 100 DPI Hi-Resolution Scan of same 8 hits found 4800 DPI- 528 hits
Comparison of droplet spatial distribution between 2 machines- 2 cm scans in the least-covered areas (still hundreds of drops/cm2)
Multifan- typical “low coverage” area.Good spatial distribution, good overall coverage.
Polygons indicate the spatial distribution around each drop
Electrostatic- fewer measured hits but stillgood spatial distribution. Achieved with less than ¼ of the carrier water of the others.
Examples: DRT/ Total Environmental Load Reduction Systems
l Adjusting the spray dosage for the canopy prior to application, e.g. to spray to the first point of runoff only
l Adjust dosage to the canopy during appln., e.g. electronic eyes and sensors shown in US, China and Europe to reduce spray losses by ~50%. Dose adjustments can be achieved by turning nozzles on and off (e.g. PWM). Some sprayers capture, recycle and reapply spray that misses the canopy.
l Targeted air (e.g. converging airflow; towers; deflectors)l Electrostatic charging under low wind speed and low evaporation conditionsl Tunnel and shielded sprayersl Multi-row sprayers to apply rapidly while weather is optimall Spraying when wind is perpendicular to tree rows and not along the rows (this
needs to be in context of the location of the sensitive area downwind)
Portable X-Ray Fluorescence
• In-situ (non-destructive and avoids need for artificial collectors with their own collection efficiency issues)• Multiple cations – can compare several sprayers under similar meteorological conditions• Rapid processing (<1 minute per sample)• Audit of spray deposition and coverage in field
Summary
l Managing diseases and pathogens in orchards while not exceeding off-target exposure, losses or residues and while avoiding resistance development requires careful consideration of cultural practices, pesticide application timing, equipment and tank mix choice
l Calibration/ dosing and auditing of spraying and spray performance can support optimized control without adverse impacts or over/ under-dosing