Sublethal effects of four synthetic insecticides on the generalist predator Cyrtorhinus lividipennis

Abstract

Cyrtorhinus lividipennis Reuter, an important predator of rice planthopper and leafhoppers, plays a significant role in the integrated pest management (IPM) of rice pest. However, chemical control remains a major strategy against rice pests. Insecticide risk assessment should include sublethal effects on non-target organisms before being included in IPM schemes. We examined the sublethal effects of four insecticides, triazophos, deltamethrin, chlorantraniliprole, and pymetrozine on C. lividipennis. The results demonstrated that sublethal concentrations of deltamethrin (LC20 and LC10) disrupted the orientation behavior of C. lividipennis, but sublethal concentrations of triazophos (LC20 and LC10), chlorantraniliprole, and pymetrozine (the recommended field rate and half field rate) had no impact on the behavioral response of surviving predators. The mean consumption of C. lividipennis treated with sublethal concentrations of triazophos decreased approximately 18–35 % compared to that of untreated ones. Sublethal concentrations of deltamethrin also reduced the mean consumption of C. lividipennis, but sublethal concentrations of chlorantraniliprole and pymetrozine exhibited no influence on the predatory capability of the predator. Significant reductions in pepsin activity were observed in triazophos and deltamethrin treatments but not in chlorantraniliprole and pymetrozine treatments. Our results indicated that triazophos and deltamethrin exerted sublethal effects, such as disturbed foraging ability, reduced predatory capacity, and decreased pepsin activity on C. lividipennis, and chlorantraniliprole and pymetrozine were regarded as safer to this predator.