avoiding spray drift
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Avoiding Spray Drift. Using phenoxy’s safely Peter Willmott and David Stephenson PIRSA Biosecurity – Rural Chemicals. Summer Weed Spraying. Rainfall on 12-14 December germinated annual weeds and freshened perennials - PowerPoint PPT PresentationTRANSCRIPT
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Avoiding Spray Drift
Using phenoxy’s safely
Peter Willmott and David StephensonPIRSA Biosecurity – Rural Chemicals
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Summer Weed Spraying
• Rainfall on 12-14 December germinated annual weeds and freshened perennials
• Around 90,000 ha sprayed from late December to late January 2009 within 30km of Clare Valley
• 2,4-D ester, amine, triclopyr, glyphosate
• Damage to vines throughout Clare Valley
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Extent of damage
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Purchase of chemicals
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Label Requirements for 2,4-D
For all 2,4-D• DO NOT use unless wind speed is more than 3 kilometres per hour
and less than 15 kilometres per hour as measured at the application site.
• DO NOT apply with smaller than coarse to very coarse spray droplets according to the ASAE S572 definition for standard nozzles.
Additional requirements for HVE• DO NOT apply this product between 1 September and 30 April. Use
only within the SPRAY WINDOW between 1 May and 31 August.• DO NOT apply this product by air.• Within 24 hours of completing a 2,4-D ethyl, butyl or isobutyl ester
application all users must make and keep a record of each application.
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Recommended conditions
Buffer distances
Spraying near sensitive crops should occur only when the wind is blowing positively away from the crop, and not closer than– 100m for amine
– 1.5km for LV ester.
These distances can be reduced to 20m and 100m in winter
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Methods of Drift
• ‘Classical’ spray drift
• Vapour drift
• Microdroplet drift
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Vapour Drift
• HVE (eg Estercide 800) volatilises at 22°C• LVE (eg Estercide Xtra 680) volatilises at 28°C• Triclopyr similar to LVE• Amines are essentially non volatile
• Volatilisation occurs if the temperature rises above the threshold after application for at least the next day.
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Microdroplet drift
• Microdroplets are the very fine droplets (mist) produced by all nozzles
• In calm conditions, the droplet can remain suspended in the air
• In low humidity or at higher temperatures, these droplets can evaporate, with the active suspended in the air
• In unsettled conditions, the droplet can rise on warm air and travel on the wind
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Spraying conditions
• Maximum forecast temperature• Temperature at time of application• Relative humidity (delta T)• Wind speed at time of application• Wind shift and variability during application• Temperature inversions• Spray quality – nozzle size• Boom height (speed)
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Observations at Clare BOM
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Opportunities to spray
Key message
there are more opportunities to use amine than LVE
LVE Amine
1am 36% 80%
6am 29% 75%
9am 20% 43%
3pm 0% 0%
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Consistent wind
3 January 2009
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Series1
Series2
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Calm conditions/inversion
6 January 2009
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Variable wind/possible inversion
4 January 2009
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Series2
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General Duty
• The Act provides for a General Duty that chemical users must take all reasonable and practical measures to not cause harm to land, plants, livestock or people through their use of chemicals, particularly through off-target damage
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Future actions
• Label changes
• Education
• Air monitoring
• Record keeping