Sublethal and transgenerational effects of thiamethoxam on the demographic fitness and predation performance of the seven-spot ladybeetle Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Abstract

Seven-spot ladybird beetles, Coccinella septempunctata L., are critical aphidophagous predators in the agricultural environment. Thiamethoxam, a neonicotinoid insecticide, is commonly used for controlling pests but impairs their natural enemies at the same time. To improve effective IPM (integrated pest management) strategies, we evaluated the sublethal and transgenerational effects of thiamethoxam on C. septempunctata. Our results showed that thiamethoxam at doses of 0.1 × LC10 (0.053 mg L−1) and LC10 (0.53 mg L−1) significantly reduced adult emergence, fecundity and fertility of the parental generation. In unexposed progeny (F1) of thiamethoxam-exposed parents, at the two doses 0.1 × LC10 and LC10, the larval stage was prolonged, and total longevity was decreased by 18.76 and 24.46%, respectively. The higher concentrations (0.1 × LC10 and LC10) also decreased the fecundity by 33.74 and 46.56%, respectively, and the oviposition period by 19.67 and 25.01%, respectively. In addition, demographic parameters including the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean generation time (T) were significantly reduced when exposed to LC10. Moreover, the predation activity of the F1 generation was reduced by the transgenerational effects of LC10. These results disclose negative influence of thiamethoxam at sublethal concentrations on this ladybird predator and its subsequent generation.