Pesticide drift deposition in hedgerows from multiple spray swaths

A series of spray experiments was conducted in order to determine deposition at different heights of the hedgerow and to estimate the effect of unsprayed buffer zones on spray deposition. Deposition varied highly with distance, absolute humidity, height, droplet size distribution and wind speed. Eighty-two percent of the observed variation could be accounted for by these factors. Droplet size distribution depended on nozzle type and working pressure, which confirms the potential of these factors for reducing spray drift. Unsprayed buffer zones reduced deposition in hedgerows, but the effect was more pronounced in the lower parts, where a reduction of 72% was obtained by introducing a 12 m buffer zone, whereas at 4 m height the reduction was less than 1%. Therefore, deposition at different heights of the hedgerow should be included in order to make risk assessments relevant for organisms exploiting different parts of the hedgerow. (C) Pesticide Science Society of Japan