Droplet size and leaf morphology effects on pesticide spray deposition

Studies were conducted to determine the effects of droplet size, leaf morph ology, and a spray thickener on pesticide spray deposition using chlorpyrif os as the indicator compound. The predicted deposition efficiencies for 140 mu m droplets were 99, 77, 65, and 55%, respectively, for cocklebur; entir eleaf morninglory, velvetleaf; and coffee senna leaves. Predicted depositio n efficiencies decreased as droplet size increased for all four leaf types. The slopes of the linear regression equations indicated that deposition ef ficiency would decrease by 16, 10, 8, and 6%, respectively, with each 100 m u m increase in droplet diameter. Addition of a viscosity modifying adjuvan t did not improve the deposition efficiency on coffee senna leaves.