The effects of five economically important vegetable (seed) oils, peanut, cottonseed, castor, soybean and sunflower, on adult and immature stages of the sweetpotato whitefly (Bemisia tabaci (Gennadius) [Hemiptera: Aleyrodidae]) were studied in the laboratory. Irrespective of origin, oil residues had similar effects on immature stages and adult mortality, and on settling and oviposition deterrence. Trends for 5-h settling, 24-h oviposition and 24-h survival of adults on treated plants were similar for oils applied at the same concentration range. Settling deterrence was strong enough to cause adult death due to starvation or dehydration under no-choice conditions, and caused greater mortality than direct physical toxicity; similar results were obtained when adult survival on oil residues was compared to survival of starved adults. Adults recovered when transferred from oil-treated to untreated plants. All oils produced similar effects when sprayed on immatures; the egg and fourth instar (pupa) were the most tolerant stages. The oil concentration required for significant effects on whitefly mortality and behavior was relatively high (>0.3%) compared with published efficacy data for synthetic pesticides, and varied to some extent with oil origin. All tested oils were active as direct and residual larvicides. Peanut oil was the most effective for all tested effects, followed by cottonseed oil, which was significantly less effective than peanut and castor oils when applied-directly to eggs. Only by this latter parameter was castor oil more effective than cottonseed oil and similar to peanut oil. As direct sprays to larvae, soybean and sunflower oils resembled castor oils, but their residues were less effective against all stages. [ABSTRACT FROM AUTHOR]