Abstract: Plant secondary metabolites play important roles in plant-insect relationships. Some plant-based extracts are insect repellents or have fumigant or contact toxicity. β-asarone is the main active ingredient of Acorus calamus L., a commonly used Chinese traditional medicinal herb. In this study, the knockdown and lethal impacts of β-asarone on four main stored-grain insects, Sitophilus zeamais, Rhyzopertha dominica, Tribolium castaneum and Callosobruchus maculatus were assayed in the laboratory. The study results showed that β-asarone extracted from A. calamus rhizome had significant knockdown and lethal impact on the pests. After the pests were treated with β-asarone for 120 h at the concentration of 50 μL/L, 100% of the C. maculatus, S. zeamais and R. dominica adults, and 50% of T. castaneum adults were knocked down; the mortality rates of T. castaneum, S. zeamais, R. dominica and C. maculatus adults were 8.89%, 81.23%, 97.78% and 100%, respectively. After 24 h exposure, the KC₅₀ values for S. zeamais, R. dominica, T. castaneum and C. maculatus adults were 49.38, 102.96, 124.04 and 1.07 μL/L, respectively. After 120 h exposure, the LC50 values for S. zeamais, R. dominica, T. castaneum and C. maculatus adults were 17.82, 4.42, 116.48 and 0.73 μL/L, respectively. It is so concluded that the β-asarone extracted from A. calamus has distinct fumigant toxicity against all the four pests assayed, and thus can be exploited as a potential fumigant.

Key words: tored-grain insects, Acorus calamus, botanical insecticides, β-asarone, fumigant toxicity