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

Abstract

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 LD30 of F0, F5, F10 and F15 generations were 0.039, 0.136, 0.243, 0.417 μg adult−1, respectively. The LD50 of F0, F5, F10 and F15 generations were 0.072, 0.275, 0.435, 0.819 μg adult−1, respectively. The resistance ratio of the F15 generation was 11.4-fold higher than that of the F0 generation. The preadult duration ( F0 = 17.4 d, F5 = 20.0 d, F10 = 19.1 d, F15 = 18.0 d) and adult preoviposition period ( F0 = 7.39 d, F5 = 8.07 d, F10 = 9.32 d, F15 = 8.03 d) of C. septempunctata were prolonged, and the fecundity ( F0 = 1690.10, F5 =1686.93, F10 = 1119.40, F15 = 752.87), oviposition period ( F0 = 42.84 d, F5 =40.33 d, F10 = 40.72 d, F15 = 30.84 d) and total longevity ( F0 = 86.7 d, F5 =81.3 d, F10 = 82.0 d, F15 = 74.0 d) were reduced by long-term exposure to sublethal dosage (LD30) of thiamethoxam. Population parameters (r, λ, R0, and T) were significantly reduced in F5, F10 and F15 generation. In addition, the predation function of F15 generation was reduced by sublethal dosage exposure of thiamethoxam. These results showed the negative impacts of sublethal thiamethoxam on the offspring of predators.