Management of khapra beetle, Trogoderma granarium Everts, using binary combinations of chitin synthesis inhibitors and inert dusts

Abstract

Control of Trogoderma granarium is difficult due to its high tolerance to all common insecticides. This problem can be partially overcome using binary combinations of insecticides with other control measures and products. In this study, three chitin synthesis inhibitors (CSIs), chlorfluazuron (CH), hexaflumuron (HE) and lufenuron (LU), and three inert dusts, diatomaceous earth (DE), zeolite (ZE) and kaolin (KA) and their combinations were assessed on stored wheat for the control of T. granarium. The three CSIs were tested at 2.5 and 5.0 mg/kg and the three inert dusts at 500 and 1000 mg/kg. The mortality of T. granarium larvae was counted after 7 and 14 days. The adult emergence (F1 progeny) from treated larvae was examined after 30 days, while F2 progeny and wheat weight loss were recorded after 80 days of exposure. The results showed that the treatments of wheat grains with individuals and combinations of CSIs and inert dusts caused remarkable mortality of T. granarium larvae after 14 days of exposure. Also, the combinations of CSIs and inert dusts were significantly more effective than those of products alone. The combinations (5.0 mg/kg of CH + 1000 mg/kg of DE and 5.0 mg/kg of LU + 1000 mg/kg of DE) induced a complete larval mortality after 14 days. Furthermore, individual and binary combinations decreased the adult emergence (F1 and F2 progeny) from T. granarium larvae and the complete inhibition of progeny was obtained in the treatments with CH or LU alone or with their combinations with the three inert dusts. After 80 days of exposure, all individual and binary treatments of CSIs and inert dusts particularly CH and LU, induced a complete wheat protection with weight loss of 0.0%. Our findings indicate that the binary combinations could be successfully applied in IPM strategies of this invasive insect species.