Spray Drift

The presence of a hazardous inversion during spray application can lead to long-distance spray drift. To detect and report hazardous inversions, specialised Profiling Automatic Weather Stations are required.

Pesticide can move considerable distances from the site of application. The extensive visual damage to viticultural and horticultural crops and residential garden plants is evidence of a larger problem of residues in fresh produce, wine and meat. There is also the risk of pesticide contamination of rainwater, with many regional households reliant solely on rainwater for drinking and other domestic uses. Estimates of the potential loss in value from spray drift were in the order of $180M per annum in the Mid North region of SA alone.

Pesticide drift occurs due to a number of factors including, product formulation (volatisation), spraying in inappropriate weather conditions and the incorrect choice of spray droplet size. There has been significant effort to reduce the use of volatile pesticides. Highly volatile herbicides are no longer permitted to be purchased or applied across most of regional SA. There has also been a concentrated education program targeting spray operators on achieving optimum droplet size, choice of nozzle types and operating pressures to reduce drift. Until now, the missing part of the puzzle was the provision of accurate weather data and warning systems of the presence of conditions likely to result in drift, this mainly being hazardous inversions and sea breezes.

It is the responsibility of spray applicators to maintain records and determine that sprays will be applied in accordance to the label. Spray applicators must read the product label prior to application. It is an offence under the SA Agricultural and Veterinary Products (Control of Use) Act 2002 to contravene a mandatory instruction on the approved label of a registered agricultural chemical product. However, until now, spray applicators were unable to access reliable information about hazardous inversion and therefore may have unwittingly been responsible for off-target contamination because of the inappropriate weather conditions.

A tractor spraying a green field – by Sebastian Czapnik
A tractor spraying a green field – by Sebastian Czapnik