Air-assisted electrostatic application of pyrethroid and endosulfan mixtures for sweetpotato whitefly (Homoptera: Aleyrodidae) control and spray deposition in cauliflower

Pyrethroid and endosulfan mixtures applied at full and reduced rates with 3 application methods (air-assisted electrostatic, air-assisted hydraulic, and standard hydraulic sprayers) were evaluated in field studies in 1992 and 1993 for control of sweetpotato whitefly, Bemisia tabaci strain B (Gennadius), also known as silverleaf whitefly, Bemisia argentifolii Bellows & Perring, and spray deposition on cauliflower, Brassica oleracea L. Evaluations of sweetpotato whitefly control were based on adult suppression, immature colonization, and cauliflower harvests. Spray deposition and coverage on abaxial and adaxial leaf surfaces was measured with a leaf wash technique and water sensitive cards placed on leaves near the terminal and base of plants. Depending on how control was assessed, the air-assisted electrostatic application technique did not consistently improve sweetpotato control when compared with hydraulic application equipment. Based on adult suppression, improved control of whiteflies was achieved with full and reduced rates of the air-assisted electrostatic sprayer following 2 applications in 1992, but percentage of reduction of adults did not differ significantly among the application methods when full rates of insecticide were applied in 1993. Control based on immature colonization indicated that the air-assisted electrostatic sprayer was the only spray method to reduce significantly nymph densities when compared with the control in 1992, but differences in numbers of eggs, nymphs, and eclosed pupal cases varied among application methods and rates of active ingredient in 1993. Comparisons of cauliflower harvest dates indicated that the air-assisted electrostatic sprayer did not provide significantly better control than the other application methods when used at similar rates. Spray deposition with the air-assisted electrostatic application technique was variable throughout these studies with no clear trends being observed. Our results suggest the air-assisted electrostatic sprayer may offer a means to control sweetpotato whitefly with a 50% reduction in insecticide usage.