Bioactivities of methyl allyl disulfide and diallyl trisulfide from essential oil of garlic to two species of stored-product pests, Sitophilus zeamais (Coleoptera : Curculionidae) and Tribolium castaneum (Coleoptera : Tenebrionidae)

Two of the major constituents of the essential oil of garlic, Allium sativu m L., methyl allyl disulfide and diallyl trisulfide, were tested against Si tophilus zeamais Motschulsky and Tribolium castaneum (Herbst) for contact t oxicity, fumigant toxicity, and antifeedant activity. The contact and fumig ant toxicities of diallyl trisulfide were greater than that of methyl allyl disulfide to the adults of these two species of insects. These two compoun ds were also more toxic to T. castaneum adults than to S. zeamais adults. O lder T. castaneum larvae were more susceptible to the contact toxicity of t he two compounds, whereas younger larvae were more susceptible to the fumig ant toxicity of these compounds. Both compounds reduced egg hatching of T. castaneum and subsequent emergence of progeny. Diallyl trisulfide totally s uppressed egg hatching at 0.32 mg/cm(2), and larval and adult emergence at 0.08 mg/cm(2). Methyl allyl disulfide significantly decreased the growth ra te, food consumption, and food utilization of adults of both insect species , with feeding deterrence indices of 44% at 6.08 mg/g food for S. zeamais a nd 1.52 mg/g food for T. castaneum. However, it did not affect any nutritio nal indices of T. castaneum larvae. Diallyl trisulfide significantly reduce d all of the nutritional indices in all of the insects tested. Feeding dete rrence indices of 27 and 51% were obtained in S. zeamais adults and T. cast aneum larvae, respectively, at the concentration of 2.98 mg/g food, whereas feeding deterrence of 85% was achieved in T. castaneum adults at a much lo wer concentration of 0.75 mg/g food. Hence, diallyl trisulfide is a more po tent contact toxicant, fumigant and feeding deterrent than methyl allyl dis ulfide.