Abstract: Biological activity of capsaicin and its effects on development and fecundity in Bemisia tabaci were tested in the laboratory. The results showed that capsaicin induced direct mortality in different developmental stages of B. tabaci, and the mortality of whiteflies were significantly dosage-dependent. The toxicity of capsaicin to different developmental stages of B. tabaci by either leaf-dip or egg/larval-dip bioassays (the LC50 for adult, egg and nymph were 3525.79, 1603.29 and 152627 mg·L-1, respectively) was higher than that by systemic bioassay (the LC50 for adult, egg and nymph were 5360.04, 2359.19 and 5897.43 mg·L-1, respectively），and toxicity of capsaicin to eggs was higher than to adults in both bioassay methods. 2000 and 4000 mg·L-1 concentrations of capsaicin had strong antifeedant effect on B. tabaci, as exemplified by reduced honeydew excretion of adults feeding on leaves treated with capsaicin compared with untreated leaf discs. Capsaicin also had strong oviposition deterrence against B. tabaci, with 94.2% of selective oviposition deterrence rate and 83.0% of nonselective oviposition deterrence rate when exposed to 4000 mg·L-1 concentration for 24 h. We did not find effect on development time of B. tabaci eggs and nymphs, and on molting rate of adults when exposed to capsaicin at 500, 1000 and 2000 mg·L-1 concentrations, however, exposure to 4000 mg·L-1 concentration of capsaicin significantly affected development time of B. tabaci nymphs and molting rate of adults. Exposure to capsaicin also significantly reduced fecundity of B. tabaci adults, and this reduction was significantly dosage-dependent.

Key words: capsaicin, Bemisia tabaci, antifeedant effect, oviposition deterrence, development, fecundity