AIR-ASSISTED ELECTROSTATIC APPLICATION OF PYRETHROID AND ENDOSULFAN MIXTURES FOR SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE) CONTROL ANDSPRAY DEPOSITION IN CAULIFLOWER

Pyrethroid and endosulfan mixtures applied at full and reduced rates w ith 3 application methods (air-assisted electrostatic, air-assisted hy draulic, and standard hydraulic sprayers) were evaluated in field stud ies in 1992 and 1993 for control of sweetpotato whitefly, Bemisia taba ci strain B (Gennadius), also known as silverleaf whitefly, Bemisia ar gentifolii Bellows & Perring, and spray deposition on cauliflower, Bra ssica oleracea L. Evaluations of sweetpotato whitefly control were bas ed on adult suppression, immature colonization, and cauliflower harves ts. Spray deposition and coverage on abaxial and adaxial leaf surfaces was measured with a leaf wash technique and water sensitive cards pla ced on leaves near the terminal and base of plants. Depending on how c ontrol was assessed, the air-assisted electrostatic application techni que did not consistently improve sweetpotato control when compared wit h hydraulic application equipment. Based on adult suppression, improve d control of whiteflies was achieved with full and reduced rates of th e air-assisted electrostatic sprayer following 2 applications in 1992, but percentage of reduction of adults did not differ significantly am ong the application methods when full rates of insecticide were applie d in 1993. Control based on immature colonization indicated that the a ir-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 va ried among application methods and rates of active ingredient in 1993. Comparisons of cauliflower harvest dates indicated that the air-assis ted 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 w as variable throughout these studies with no clear trends being observ ed. Our results suggest the air-assisted electrostatic sprayer may off er a means to control sweetpotato whitefly with a 50% reduction in ins ecticide usage.