Population‐specific variation in temperature‐dependent RNAi efficacy in the Colorado potato beetle ( Leptinotarsa decemlineata )

Abstract BACKGROUND The Colorado potato beetle (CPB), Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is a major pest of potato and other nightshades (Solanaceae). CPB's remarkable ability to rapidly evolve resistance to conventional insecticides has necessitated the development of novel management strategies, including RNA interference (RNAi)‐based approaches using insecticidal dsRNA. In previous work, we demonstrated that a dsRNA insecticide targeting Actin, a highly conserved protein essential for cell structure and function, was less effective at low temperatures. Here, we evaluated the extent to which the temperature‐dependence of RNAi in CPB varies among geographically distinct populations. Our goal was to quantify genotype × environment interactions underlying RNAi efficacy, which could influence regional pest management efficacy and be a pathway to resistance. RESULTS We measured gene silencing and mortality for three populations of CPB (Vermont, Kentucky and Oregon) following ingestion of dsRNA targeting Actin at 18 and 25 °C. At 25 °C, gene silencing occurred more quickly in the Vermont population but mortality did not vary significantly among populations. ds Actin was more toxic for all populations at 25 °C relative to 18 °C. At 18 °C, the Kentucky population died faster than those from Vermont and Oregon. The estimated consumed dose of insecticidal dsRNA was not an effective predictor of gene silencing or mortality across populations. CONCLUSION RNAi insecticides may function less efficiently at cooler temperatures, and the precise effects of temperature could vary across CPB populations. Although all three populations reached the same levels of mortality at pupation, the rate at which larvae died varied significantly, which could impact the degree of herbivory and affect agricultural yields, particularly if applications occur early in the growing season when the weather is cooler. © 2026 Society of Chemical Industry.