ABSTRACT

Significant outbreaks of the poinsettia strain of sweetpotato whitefly, Bemisia tabaci (Gennadius), in Arizona, California, and Texas in 1991 led to an intensified research effort to improve application technology to control this new pest of cotton. Increased spray deposition on the bottom of leaves and deeper into the crop canopy is needed to improve control of B. tabaci. Reduced airspeed and Chimavir winglets, which increase wake intensity in the crop canopy during spray application, were evaluated for increased spray deposits from insecticide applications with a fixed-wing aircraft. Deposit measurements from leaf washes and water sensitive paper, both on the top and bottom of leaves, at the top and midway down in the crop canopy show that the major portion of spray is deposited on the top of leaves. The treatments with higher wake intensity increase deposits on the bottom of leaves an average of 50 percent, but the amounts deposited there are relatively low compared to total spray deposits.