Spray drift of pesticides arising from aerial application in cotton

This paper presents results from field studies carried out during the 1993- 1998 Australian cotton (Gossypium hirsutum L.) seasons to monitor off-targe t droplet movement of endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-he xahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) insecticide applied to a commercial cotton crop. Averaged over a wide range of conditions, off-ta rget deposition 500 m downwind of the field boundary was approximately 2% o f the field-applied rate with oil-based applications and 1% with water-base d applications. Mean airborne drift values recorded 100 m downwind of a sin gle night line were a third as much with eater-based application compared w ith oil-based application. Calculations using a Gaussian diffusion model an d the U.S. Spray Drift Task Force AgDRIFT model produced downwind drift pro files that compared favorably with experimental data. Both models and data indicate that by adopting large droplet placement (LDP) application methods and incorporating crop buffer distances, spray drift can be effectively ma naged.