Responses to azadirachtin and pyrethrum by two species of Bemisia (Homoptera: Aleyrodidae)

The effects of pyrethrum and azadirachtin on the ovipositional responses of Bemisia argentifolii Bellows & Perring and Bemisia tabaci (Gennadius) were determined in the laboratory. Choice and no-choice tests revealed that neither B. argentifolii nor B. tabaci females preferred to alight and oviposit on bean plants treated with pyrethrum. In contrast, the number of B. argentifolii females that alighted on control versus azadirachtin-treated plants was not significantly different in all but 1 instance. When given a choice, significantly fewer B. tabaci females 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 choice and no-choice trials, B. tabaci females laid significantly fewer eggs on plants treated with azadirachtin. Percentage nymphal establishment of B. argentifolii on control versus azadirachtin-treated plants was not significantly different in choice and no-choice trials. Although the percentages of established B. tabaci nymphs were the same on control and azadirachtin-treated plants in the no-choice test, a significantly lower percentage of nymphs were found on treated plants in the choice trials.