Transgenerational hormesis and sublethal effects of five key insecticides for controlling Spodoptera frugiperda on its endoparasitoid Cotesia marginiventris.

Background: The endoparasitoid Cotesia marginiventris (Cresson) is a promising biological control agent of the fall armyworm (FAW) Spodoptera frugiperda (Smith). Because the application of insecticides is one of the prime choices in pest management, we evaluated the sublethal and transgenerational effects of the five key insecticides-chlorantraniliprole, emamectin benzoate, spinetoram, Bacillus thuringiensis (Bt), and Mamestra brassicae nucleopolyhedrovirus (MbNPV)-on the parasitoid.

Results: Exposure to five insecticides at a concentration causing 10% mortality (LC ) caused hormetic effects in the parent generation (F ) by increasing the parasitism and reducing the immature duration. Interestingly, the hormetic response was also observed in the offspring generation indirectly exposed to the insecticides. Furthermore, insecticides increased the parasitism rate by 6.32-14.73% in the F generation, which was similar to that of the F generation (3.96-11.81%) compared with the control. No significant adverse effect was observed on the number of emerged parasitoids of the F and F generations. However, insecticides had a detrimental impact on body size and fecundity in the F and F generations, which showed a small body size with shorter hind tibiae and a significant reduction in the female ratio compared with the control; the exception was that chlorantraniliprole significantly improved the female ratio in the F generation.

Conclusions: Five insecticides at LC induced transgenerational hormetic and sublethal effects on C. marginiventris. Our results provide a scientific basis for a better understanding of the long-term impacts of insecticides at sublethal doses on parasitoids, facilitating the development of improved integrated pest management programs for FAW control. © 2023 Society of Chemical Industry.