Chitosan-protected dsRNA increases efficacy against Helicoverpa armigera without compromising biosafety for...

Cotton bollworm, Helicoverpa armigera, is a major global pest of cotton. Delivery of double-stranded RNA (dsRNA) shows promise as a biopesticide for controlling this insect pest. However, employing RNA interference (RNAi) technology in the field requires enhancing its stability and demonstrating biosafety.

Two genes, chitin synthase II and cytochrome p450 protein 6b6, were simultaneously targeted to disrupt the gut physiology of the cotton bollworm. Long dsRNA molecules (≈ 400 bp) encapsulated with a cationic polymer (chitosan) and a cross-linker (tripolyphosphate, TPP) were synthesized to produce nanoparticles ranging from 150 to 300 nm in size, with a positive charge ~40 mV. Encapsulation resulted in a 100% increase in the knockdown effect on larvae that were fed with a diet containing dsRNA-nanoparticle complex compared to those fed with naked dsRNA. Additionally, nanoparticles produced substantially higher mortality than naked dsRNA, even at 100-fold lower concentration. Overall, our findings suggest that chitosan/TPP/dsRNA nanoparticles at low doses (0.1-1 μg g^-1) effectively enhance the RNAi effect in H. armigera larvae via oral delivery. In addition, acute oral toxicity tests were conducted on two relevant beneficial bees, Scaptotrigona postica and Bombus terrestris. Consistent with predictions from bioinformatic analyses, no significant lethality or signs of toxicity were observed in these non-target organisms.

Delivery of dsRNA molecules via nanoparticles was demonstrated to be a promising approach to enhance RNAi activity against H. armigera. Thus, this technology represents an efficient and safe strategy for managing lepidopteran pests. However, further research to optimize these molecules for field application is crucial. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.