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Avoiding Spray Drift

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

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Avoiding Spray Drift

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  1. Avoiding Spray Drift Using phenoxy’s safely Peter Willmott and David Stephenson PIRSA Biosecurity – Rural Chemicals

  2. 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

  3. Extent of damage

  4. Purchase of chemicals

  5. 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 mustmake and keep a record of each application.

  6. 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

  7. Methods of Drift • ‘Classical’ spray drift • Vapour drift • Microdroplet drift

  8. 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.

  9. 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

  10. 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)

  11. Observations at Clare BOM

  12. Opportunities to spray Key message there are more opportunities to use amine than LVE

  13. Consistent wind

  14. Calm conditions/inversion

  15. Variable wind/possible inversion

  16. 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

  17. Future actions • Label changes • Education • Air monitoring • Record keeping

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