Chitosan-dsRNA Nanoparticles Targeting SlChitinase5 Enhance Insecticide Efficacy Against Spodoptera litura

Spodoptera litura is a highly destructive agricultural pest with increasing reliance on chemical insecticides. We aimed to develop nanotechnology-enabled strategies that enhance insecticide efficacy against S. litura and reduce chemical inputs. To this end, SlChitinase5 was identified and characterized as a potential RNAi target. This gene contains conserved domains typical of lepidopteran chitinases and is highly expressed during key developmental stages, including larval molting and the prepupal phase. RNAi-mediated suppression of SlChitinase5 through larval injection of double-stranded RNA (dsSlChitinase5) significantly reduced body weight, increased mortality, and disrupted molting. When RNAi-treated larvae were exposed to sublethal concentrations of emamectin benzoate (EB) or an emamectin benzoate–tebufenozide mixture (EBT), larval mortality reached 96.7% on day 5. To evaluate an alternative formulation and exposure approach, dsSlChitinase5 was incorporated into chitosan nanoparticles (CS) and applied topically. This treatment induced SlChitinase5 knockdown and, in combination with sublethal EB or EBT, resulted in complete larval mortality within five days under the conditions tested. These findings validate SlChitinase5 as a molecular target and suggest that CS-dsSlChitinase5 nanocarriers have the potential to enhance insecticide performance, which may support integrated pest management and future efforts toward reduced-input crop protection strategies.