Development and efficacy of dsRNA pesticides targeting the Colorado potato beetle with enhanced stability via chitosan formulations.

The Colorado potato beetle (CPB, Leptinotarsa decemlineata) is a major pest of solanaceous crops and has developed resistance to many conventional insecticides, highlighting the need for novel, environmentally sustainable control strategies. In this study, we evaluated the efficacy of RNA interference (RNAi) targeting the proteasome subunit β5 (PSMB5) gene as a biopesticide approach against CPB larvae. Double-stranded RNA (dsRNA) targeting PSMB5 (a highly specific dsRNA) and Actin (a less specific dsRNA) dsRNA was synthesized and applied via leaf dip assays, either in naked form or formulated with chitosan nanoparticles. Feeding assays showed that dsRNA-PSMB5 induced significant target gene knockdown, with over 80 % transcript reduction within 120 h. Chitosan-formulated dsRNAs exhibited improved stability against gut nucleases, ultraviolet (UV) light and elevated temperatures. While naked dsRNAs induced faster larval mortality, chitosan formulations provided prolonged gene silencing, reduced feeding, and consistent larval growth suppression. Bioassays yielded LC₅₀ values within practical application ranges, and a greenhouse trial confirmed feeding suppression at a field-relevant concentration. These findings support chitosan-formulated dsRNA targeting PSMB5 as a promising RNAi-based biopesticide for CPB management and contribute to the development of RNAi technologies for sustainable pest control.