Improving RNAi in the fall armyworm, Spodoptera frugiperda

The rising incidence of resistance to conventional chemical insecticides necessitates the development of novel, sustainable pest management strategies. RNA interference (RNAi) offers a highly specific alternative; however, its practical application in lepidopteran pests is often limited by low efficacy due to rapid dsRNA degradation, inefficient transport of dsRNA to the site of action, and suboptimal target gene selection. While nanoformulated dsRNA has been shown to improve RNAi efficiency, delivery enhancement alone does not consistently result in high mortality. In the current study, we used PLL/EGCG/dsRNA nanoformulations to improve RNAi-based control of S. frugiperda. We first validated the effectiveness of nanoparticle-mediated RNAi in S. frugiperda by targeting the inhibitor of apoptosis (IAP) gene. Nanoformulated dsRNA targeting IAP resulted in substantial gene silencing, with an 80% reduction in target gene mRNA levels and 63% larval mortality, confirming that improved dsRNA delivery can significantly enhance RNAi efficacy in lepidopterans. We extended our analysis to evaluate an additional 14 candidate genes selected from recent genome-wide RNAi screens that identified superior RNAi targets. Orthologs of these genes in S. frugiperda, including proteasome subunit β-type 4 (BT4) and 60S ribosomal protein L11 (RPL11), were targeted using PLL/EGCG/dsRNA nanoformulations. Although these genes induced moderate larval mortality, their effects were consistently lower than those observed with IAP, indicating that IAP remains a more effective RNAi target among the genes evaluated in S. frugiperda.