Toxic and antifeedant effects of allyl disulfide on Tribolium castaneum (Coleoptera : Tenebrionidae) and Sitophilus zeamais (Coleoptera : Curculionidae)

Toxicity and antifeedant activity of allyl disulfide, a volatile compound f rom garlic, Allium sativum, L., to adults and larvae of Tribolium castaneum (Herbst) and adults of Sitophilus zeamais Motschulsky were investigated. T opical application was used for contact toxicity, filter paper impregnation for fumigant toxicity, and a flour disk bioassay for antifeedant activity. The filter paper impregnation bioassay also was used to study the effects on egg hatch and the subsequent progeny emergence of T. castaneum. Adult T. castaneum were more susceptible to allyl disulfide than adult S. zeamais i n both toxicity tests. Allyl disulfide was 3 times more potent to T, castan eum, adults than to S. zeamais in contact toxicity tests, with LD(50)s Of 7 .16 and 22.47 mu g/mg insect, respectively. In the fumigant bioassay, allyl disulfide was approximate to 5 times more effective to the adults of T. ca staneum than to S. zeamais, with LC50 values of 0.030 and 0.146 mu mg/cm(2) , respectively. The larvae of T. castaneum, were more tolerant of allyl dis ulfide treatment than the adults in both toxicity tests. Egg hatching and s ubsequent progeny emergence from treated eggs were reduced with increasing concentrations. Allyl disulfide was a more potent antifeedant to T. castane um adults than either T. castaneum larvae or S. zeamais adults. A concentra tion of 7.43 mg/g of food deterred feeding by 85.7% among the T. castaneum adults, but feeding was deterred only by 31.5% at 12.77 mg/g of food and 21 .2% at 29.15 mg/g of food for T. castaneum larvae and S. zeamais adults, re spectively.