Activity of natural toxins against the silverleaf whitefly, Bemisia argentifolii, using a novel feeding bioassay system

An assay system was developed for the adult silverleaf whitefly, #Bemisia argentifolii# Bellows & Perring (Homoptera : Aleyrodidae). This practical device was constructed from standard disposable laboratory materials. Whiteflies were harvested directly from the leaf and into a collection vial by vacuum aspiration, minimizing physical damage to the insect. Insects were fed throueh a cellulose mixed-ester membrane on a diet of 20-27% sucrose alone or sucrose in an extract of zucchini (#Curcurbita moschata# Duchense). Mortality and honeydew production were scored. At 22-25 °C and 50-55%, relative humidity, control mortality generally remained at or below 15% during a 48 h assay period. The bioassay system was first tested using the insecticide, Imidacloprid, then used to screen a number of natural products with potential insecticidal activity against the whitefly. Destruxins extracted from the entornopathogenic fungus, #Metarhizium anisopliae#, and the natural insccticide/nematicide, Ivermectin, as well as bee venom and two of its components, melittin and phospholipase A,, were found to be toxic to #B. argentifolii#. Five lectins, #Bacillus thuringiensis# toxins, gossypol, an extract of #Paeciliomyces fumosoroseus#, wasp and scorpion venom, and a trypsin inhibitor were not found to be insecticidal to adult #B. argentifolii#. (Résumé d'auteur