DEPOSITION AND BIOASSAY OF INSECTICIDES APPLIED BY LEAF DIP AND SPRAYTOWER AGAINST BEMISIA-ARGENTIFOLII NYMPHS (HOMOPTERA, ALEYRODIDAE)

Two application methods, spray and leaf dip, were evaluated as bioassa ys for insecticides to nymphs of Bemisia argentifolii Bellows & Perrin g (formerly Bemisia tabaci Gennadius strain 'B'). Sprays were applied at different volumes and pressures with the Potter Spray Tower(R). Spr ay deposition was evaluated using a tracer dye, and also plain water i n the case of the spray tower. Coverage on water-sensitive paper was e valuated with a computerized image-scanning system. Insecticide effica cy was evaluated as mortality to whitefly nymphs. Materials assayed in cluded 'M-Pede'(R) (an insecticidal soap), 'Sunspray'(R) Ultra-Fine Sp ray Oil (a mineral oil), 'Margosan-O'(R) (an extracted concentration o f azadirachtin + 10% neem oil), and bifenthrin ('Brigade'(R) 10WP), a pyrethroid, with purified water as a control. Differing results were o btained with the two bioassay methods, depending on material tested. M ortality of whitefly nymphs from bifenthrin, and to a lesser extent ne em extract, was largely independent of application method. In contrast , 'Sunspray' (mineral) oil, and to a lesser extent insecticidal soap, was more efficacious when applied as a dip than as a spray. Difference s in respect of effects of application method on treatment mortality w ere attributed to differences between materials in mode of action.