Toxicity and sublethal effects of cyproflanilide on Cotesia chilonis (Hymenoptera: Braconidae)

The novel meta-diamide insecticide cyproflanilide is highly effective on the rice stem borer, Chilo suppressalis (Lepidoptera: Pyralidae). Nevertheless, the sublethal effects on key natural enemies, such as Cotesia chilonis (Hymenoptera: Braconidae), remain unexplored, which is critical for ecological compatibility within IPM programs. We investigated the direct and indirect effects of sublethal doses of cyproflanilide on C. chilonis. Our results revealed that the LC50 of cyproflanilide on female and male wasps of C. chilonis were 1.17 mg/L and 0.37 mg/L, respectively. After treatment of C. suppressalis with cyproflanilide, they were then parasitized by C. chilonis. Compared with control groups, the cyproflanilide treatment showed no significant differences in the number of cocoons, total number of emerged wasps (including males and females), or the parasitism rate of C. chilonis. In contrast, when C. chilonis was exposed to cyproflanilide at LC30 concentration, no significant alteration in developmental duration was observed compared to the control group. The number of cocoons by C. chilonis decreased from 47 to 34. Similarly, the number of emerged wasps decreased from 47 to 31, and the parasitism rate decreased by 9%. Our results show that the indirect effects of cyproflanilide on C. chilonis were not significant; direct contact with the insecticide poses significant risks to the C. chilonis reproductive output. Thus, it can be seen that when applying pesticides in the field, it is necessary to stagger the emergence peaks of C. chilonis and C. suppressalis, which is important for the prevention and control effect.