Abstract

Monochamus alternatus is the main vector of pine wilt disease and plays a critical role in the spread of this destructive forest disease. Developing efficient and environmentally friendly strategies to control this insect is therefore of great importance. Chitinases are key enzymes involved in insect molting and cuticle formation and are considered promising targets for RNA interference (RNAi)-based pest control. In this study, we characterized MaCht-2 , a Group VII chitinase gene in M. alternatus , and evaluated its function during development. We found that MaCht-2 was highly expressed during the fifth-instar larval and pupal stages. Silencing MaCht-2 caused severe molting failure, developmental abnormalities, impaired locomotion, and high mortality in larvae, pupae, and adults. In addition, cuticle ultrastructure was seriously disrupted after gene knockdown. These results show that MaCht-2 is essential for normal development of M. alternatus and suggest that it is a promising molecular target for RNAi-based management of this important forest pest. Monochamus alternatus , the principal vector of pine wilt disease, poses a serious threat to pine forest ecosystems, and the identification of effective molecular targets is important for the development of environmentally friendly control strategies. In this study, a Group VII chitinase gene, MaCht-2 , was identified in M. alternatus , and its developmental expression pattern, RNA interference (RNAi) efficiency, and RNAi-induced phenotypes were investigated using quantitative PCR, dsRNA injection, and transmission electron microscopy. MaCht-2 was highly expressed from the fifth-instar larval stage to the pupal stage, indicating a role in molting and metamorphosis. Silencing of MaCht-2 caused severe developmental defects across multiple life stages, including incomplete ecdysis, pupation failure, adult deformities, impaired locomotion, and high mortality. In third-instar larvae, injection of 5 μg of d