Sublethal effects of four insecticides on folding and spinning behavior in the rice leaffolder, Cnaphalocrocismedinalis (Guenée) (Lepidoptera: Pyralidae).

BACKGROUND: The rice leaffolder, Cnaphalocrocis medinalis, is an important rice pest. The sublethal effects of chlorpyrifos, chlorantraniliprole, emamectin benzoate and spinosad were investigated on the folding and spinning behaviors of third- to fifth-instar C. medinalis larvae (L3-L5) after insecticidal exposure of the second instar. RESULTS: A 25% lethal concentration (LC₂₅) of chlorpyrifos prolonged the leaf selection time of L5, and reduced the number of binds per primary fold for L4 and L5. An LC₁₀ of chlorantraniliprole reduced the number of binds per primary fold for L4 and increased the number of head swings per bind for L5. An LC₁₀ of emamectin benzoate shortened the primary fold length for L5 and decreased the number of head swings per primary fold for L3 and L4 and the number of head swings per bind for L3, while an LC₂₅ of emamectin benzoate shortened the fold length per 24 h for L5 and folding time for L3. An LC₁₀ of spinosad lowered the fold length per 24 h and the number of head swings for L5. An LC₂₅ of spinosad prolonged leaf selection time, and decreased primary fold length, binds per primary fold, binds per fold and fold length per 24 h in L5. CONCLUSION: Emamectin benzoate and spinosad exerted stronger sublethal effects on the folding and spinning behavior of C. medinalis than chlorpyrifos and chlorantraniliprole. These results provide better understanding of the sublethal effects of interactions of insecticides on C. medinalis. [ABSTRACT FROM AUTHOR]