Gut microbial dysbiosis is associated with detoxification impairment in parasitoid wasps exposed to Emamectin benzoate.

Emamectin benzoate (EB) is widely used in agricultural pest management, but its toxic effects on non-target natural enemies and the underlying mechanisms remain poorly understood. Here, we investigated the toxicity of EB to the parasitoid wasp Leptopilina drosophilae Huang, a promising biological control agent of Drosophila suzukii Matsumura and other drosophilid pests, and explored the role of gut microbiota in mediating host physiological responses. Bioassay results showed that EB exhibited high toxicity to L. drosophilae in a dose-dependent manner, with LC5, LC10, and LC50 values of 0.57 mg/L, 0.69 mg/L, and 1.32 mg/L, respectively. Transcriptomic analysis further revealed that sublethal EB exposure significantly suppressed genes related to detoxification and immunity. Consistent with these molecular changes, 16S rRNA sequencing demonstrated that EB induced severe gut dysbiosis, characterized by reduced microbial diversity and richness. Moreover, integrated correlation analysis revealed significant positive associations between the abundance of declined bacterial genera and the expression of detoxification genes, suggesting a functional link between gut microbiota disruption and impaired host detoxification capacity. Collectively, our findings demonstrate that sublethal EB exposure disrupts gut microbiota homeostasis through suppression of gut antimicrobial peptide expression, which in turn leads to downregulation of host detoxification genes and reduced insecticide resistance. This microbially-mediated mechanism contributes to the compromised fitness and increased mortality of parasitoid wasps, highlighting the ecological risks of EB to biological control agents and emphasizing the need to consider gut microbiota-mediated effects in insecticide safety assessments.