Sublethal and transgenerational effects of exposures to the thiamethoxam on the seven-spotted lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

The seven-spot ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae) has been used as the major natural enemy insect against many kinds of aphids in environment. Thiamethoxam is a second-generation neonicotinoid insecticide and commonly used to control various aphids, but it also has adverse effects on natural enemies. Therefore, the sublethal effects of thiamethoxam on the offspring of C. septempunctata were studied. For the adults of C. septempunctata, the LD(30 )of F-0, F-5, F-10 and F-15 generations were 0.039, 0.136, 0.243, 0.417 mu g adult-1, respectively. The LD50 of F-0, F-5, F-10 and F-15 generations were 0.072, 0.275, 0.435, 0.819 mu g adult-1, respectively. The resistance ratio of the F-15 generation was 11.4-fold higher than that of the F-0 generation. The preadult duration ( F-0 = 17.4 d, F-5 = 20.0 d, F-10 = 19.1 d, F-15 = 18.0 d) and adult preoviposition period ( F-0 = 7.39 d, F-5 = 8.07 d, F-10 = 9.32 d, F-15 = 8.03 d) of C. septempunctata were prolonged, and the fecundity ( F0 = 1690.10, F5 =1686.93, F-10 =1119.40, F-15 = 752.87), oviposition period ( F-0 = 42.84 d, F-5 =40.33 d, F-10 = 40.72 d, F-15 = 30.84 d) and total longevity ( F-0 = 86.7 d, F-5 =81.3 d, F-10 = 82.0 d, F-15 = 74.0 d) were reduced by long-term exposure to sublethal dosage (LD30) of thiamethoxam. Population parameters (r, lambda, R0, and T) were significantly reduced in F-5, F-10 and F-15 generation. In addition, the predation function of F-15 generation was reduced by sublethal dosage exposure of thiamethoxam. These results showed the negative impacts of sublethal thiamethoxam on the offspring of predators.

Automated summary

This study investigated the sublethal effects of thiamethoxam on the offspring of the seven-spot ladybird beetle. The results showed that prolonged exposure to sublethal dosage of thiamethoxam had negative impacts on the life cycle, reproductive capacity, and population parameters of the ladybird beetle.