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.