Additive Insecticidal Effects of Chitosan/dsRNA Nanoparticles Targeting V-ATPaseD and Emamectin Benzoate-Lufenuron Formulations Against Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).

The fall armyworm, Spodoptera frugiperda, a lepidopteran pest from the family Noctuidae, has become a major invasive pest since 2016. Using RNAi methods to control S. frugiperda is currently under investigation. This study is the first to target the V-ATPaseD gene of S. frugiperda using RNAi. Injection of dsRNA-V-ATPaseD into the hemolymph of 4th-instar larvae significantly suppressed gene expression at 24 and 48 h post-injection. Treated larvae showed delayed development and reduced pupation after 7 days. Subsequently, V-ATPaseD silencing was achieved through topical or oral administration of chitosan/dsRNA-V-ATPaseD nanoparticles. Larvae fed these nanoparticles exhibited significant reductions in V-ATPaseD mRNA at 72 h, persisting until 96 h before normalizing. Additionally, the treated larvae displayed disrupted molting and impaired pupation. Furthermore, larvae fed chitosan/dsRNA-V-ATPaseD were more susceptible to emamectin benzoate-lufenuron at LC30 concentrations, resulting in 68% mortality-27% higher than the pesticide alone-72 h post-exposure. Combining chitosan/dsRNA-V-ATPaseD nanoparticles with emamectin benzoate-lufenuron significantly enhanced pest control efficacy, providing new insights into pesticide reduction and sustainable pest control methods for this invasive species.