Responses of the Whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) to Biologically Based Insecticides

Abstract

The effects of three bio-insecticides Azatrol [neem: 1.2% azadirachtin A and B], Molt-X [neem: 3% azadirachtin], and Conserve SC [spinosad; 11.6% spinosyn A and spinosyn D], applied at different concentrations were evaluated on Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) under both laboratory and greenhouse conditions. Laboratory bioassays demonstrated that both neem-based insecticides were repellent to adult whiteflies in a dose-dependent manner. The amounts and frequency of honeydew excretion were significantly reduced up to 0.95 by foliar application of these insecticides at the labeled rate, as compared to untreated plants, with the neem products displaying greater effects on food uptake than spinosad. Reduced fecundity and egg hatch also were associated with these bio-insecticides. The bio-insecticides decreased significantly the survival of nymphs, egg hatch and adult emergence when applied systemically via the roots. However, the impacts of neem-based insecticides on all parameters tested were greater than that of spinosad. The results indicate that the biologically based formulations tested were effective in suppressing whitefly abundance and acting as an efficient repellent, though they were not able to completely inhibit food intake. The repellent and antifeedant activities of such natural products render plants unattractive to B. tabaci, thus potentially reducing the incidence of viral diseases transmitted by this pest. The systemic properties of these formulated biopesticides minimize their rapid degradation by strong ultraviolet light and their adverse effects on non-target organisms.