Lin_2026_Pest.Manag.Sci__

BACKGROUND: Beta-cypermethrin (BC) and thiamethoxam (TH) are widely applied insecticides in cover spray programs targeting tephritid pests, yet their sublethal effects on Fopius arisanus, a major fruit fly parasitoid, remain largely unexplored. Therefore, we evaluated the impacts of BC and TH on the demographics, detoxifying enzymes, nutrients, and transcriptome of F. arisanus. RESULTS: Our results demonstrated that both insecticides exerted profound adverse impacts on the fecundity, longevity, and oviposition period of F. arisanus adults. In the F(1) generation, exposure to LC(30) BC and TH significantly prolonged preadult duration, impaired preadult survival, and decreased fecundity, lifespan, APOP, R(0), lambda, and r. Nutritional analyses revealed a time-dependent depletion across all treatments, with all nutrients significantly diminished at 5 days post-exposure compared with the control. Concurrently, glutathione S-transferase (GST) and cytochrome P450 O-deethylation activities were markedly elevated under LC(30) treatment relative to the control throughout 1-3 days post-exposure. Carboxylesterase (CarE) activity was significantly increased following LC(30) BC exposure across all observation periods. In addition, lipid and carbohydrate levels were negatively correlated with CarE and GST activities at specific time points, indicating that the maintenance of detoxification occurred at the expense of nutrients. Regarding the transcriptome, 562 and 190 DEGs were identified in the BC versus control and TH versus control comparisons, respectively, with KEGG enrichment highlighting shared pathways in xenobiotic metabolism, including P450 and other enzymes. CONCLUSION: These results demonstrate that sublethal BC and TH compromises the fitness and ecological function of F. arisanus, underscoring the need for environmentally compatible pest management strategies. 2026 Society of Chemical Industry.