Effects of a Foliar Neem Formulation on Colonization and Mortality of Whiteflies (Hemiptera: Aleyrodidae) on Collard Plants

A study was conducted to determine the effects of foliar sprays of a selected neem (Azadirachta indica A. Juss) product (GOS Neem 7-Way) on colonization and development by the Middle-East Asia Minor-1 (= B-biotype sweetpotato whitefly) Bemisia tabaci (Gennadius) on collard (Brassica oleracea variety acephala de Condolle) plants. GOS Neem 7-Way is marketed for use as an insecticide in organic and conventional crop production. Caged choice, caged no-choice, and Y-tube olfactometer assays were conducted on oviposition, survival and adult behavioral response to plant treatment with 1.25% azadiractin. In the caged choice experiment, colonization by the whiteflies was reduced and fewer eggs were deposited on neem-treated plants as compared with control plants (only treated with an adjuvant). Similarly, decreased numbers of adult whiteflies and reduced whitefly development were observed in no-choice assays for the neem-treatment, as compared with the untreated control. Both horizontal and vertical-orientated Y-tube olfactometer assays provided complementarily assessments that the neem had a repellency effect on the adult whiteflies. However, the repellency effect primarily dissipated within one day post treatment. Overall, the greatest benefit of the neem treatment appears to have been on whitefly mortality. The findings may be useful in providing a more ecologically sound way to manage populations of the B. tabaci whitefly in organic vegetable production.