Synergistic effect of MnO2 nanoparticles in overcoming insecticide tolerance in Nilaparvata lugens induced by elevated CO2 concentrations

Elevated CO2 (eCO2) can alter insecticide efficacy and reduce insect susceptibility to insecticides, yet the performance of nanoparticle-assisted insecticide formulations under eCO2 conditions remains poorly understood. Here, we investigated the effects of eCO2 on clothianidin susceptibility in Nilaparvata lugens and evaluated the efficacy of MnO2 nanoparticles (NPs) co-application. Population performance, detoxification-related responses, CYP gene expression, microbial community dynamics, and preliminary non-target toxicity were analyzed under ambient CO2 (aCO2, 420 µL/L) and eCO2 (800 µL/L) conditions. eCO2 exposure was associated with an approximately 1.5-fold reduction in clothianidin susceptibility and altered microbial community composition, including enrichment of stress-associated genera such as Acinetobacter and Serratia. Co-application with MnO2 NPs enhanced clothianidin efficacy, reduced population growth, fecundity, and longevity, and was linked to suppression of detoxification-related enzyme activities and CYP gene expression. MnO2 NPs treatment also counteracted the microbial community alterations associated with eCO2, which may contribute to improved insecticide susceptibility. Acute toxicity assays in Bombyx mori showed low short-term toxicity of MnO2 NPs, with larval mortality remaining below 5% even at 800 mg/L. These findings suggest that elevated CO2 may influence insecticide susceptibility through physiological, detoxification-related, and microbiome-associated responses. MnO2 nanoparticle co-application may therefore represent a promising strategy for improving pesticide performance under future climate change scenarios.