RESPONSES TO AZADIRACHTIN AND PYRETHRUM BY 2 SPECIES OF BEMISIA (HOMOPTERA, ALEYRODIDAE)

The effects of pyrethrum and azadirachtin on the ovipositional respons es of Bemisia argentifolii Bellows & Perring and Bemisia tabaci (Genna dius) were determined in the laboratory. Choice and no-choice tests re vealed that neither B. argentifolii nor B. tabaci females preferred to alight and oviposit on bean plants treated with pyrethrum. In contras t, the number of B. argentifolii females that alighted on control vers us azadirachtin-treated plants was not significantly different in all but 1 instance. When given a choice, significantly fewer B. tabaci fem ales landed on azadirachtin-treated plants at observation hours 6, 8, and 24. In no-choice trials, numbers of B. tabaci females alighting on control versus azadirachtin-treated plants were equivalent throughout the entire test period. Moreover, although B. argentifolii oviposited equal numbers of eggs on control and azadirachtin-treated plants in c hoice and no-choice trials, B. tabaci females laid significantly fewer eggs on plants treated with azadirachtin. Percentage nymphal establis hment of B. argentifolii on control versus azadirachtin-treated plants was not significantly different in choice and no-choice trials. Altho ugh the percentages of established B. tabaci nymphs were the same on c ontrol and azadirachtin-treated plants in the no-choice test, a signif icantly lower percentage of nymphs were found on treated plants in the choice trials.