The red turpentine beetle, Dendroctonus valens LeConte, is an important phloem-feeding pest of pine forests in China. RNA interference (RNAi) is a conserved, sequence-specific gene-silencing mechanism induced by double-stranded RNA (dsRNA), and has become an important molecular tool for screening and evaluating potential targets for pest management owing to its high efficiency, target specificity, and relative environmental safety. In this study, six candidate genes were selected, including mesh and ssk responsible for gut barrier formation, actin involved in cellular structure maintenance, iap involved in apoptosis regulation, hsp70-2 responsible for stress response, and v-atpaseE involved in ion transport and cellular homeostasis. The effects of dsRNA microinjection on gene silencing and mortality were then evaluated in both larvae and adults of D. valens. Following dsRNA treatment, all six candidate genes were significantly downregulated in both larvae and adults, with v-atpaseE showing the strongest transcript suppression in larvae. Survival analysis revealed target-dependent lethal effects: v-atpaseE caused rapid larval mortality, reaching 100% by day 3, whereas ssk caused the strongest adult mortality, reaching 100% by day 5, and mesh also induced substantial adult mortality. In contrast, actin, iap, and hsp70-2 produced weaker or slower lethal effects. These results indicate that dsRNA injection can induce effective gene silencing in D. valens and that the resulting phenotypic responses differ among target genes and between life stages. Taken together, v-atpaseE and ssk represent the most promising candidate targets for further development of RNAi-based management strategies against D. valens.

Dendroctonus armandi is a native bark beetle that infests healthy Pinus armandii Franch. in western China. The complex symbiotic relationships with diverse microbes are critical to hosts for survival and outbreak dynamics. Understanding the potential functions and assembly metabolisms of these symbiotic microbes to host colonization are therefore crucial. Metagenomic analysis revealed that gut microbial communities differed from cuticular ones significantly. The cuticle exhibited greater fungal diversity, while the gut supported a significantly higher bacterial diversity. Our findings indicated that gut unclassified Burkholderiales, Escherichia, Bacteroides and Prevotella may play a crucial role in degrading terpenes, phenols and polysaccharides rather than cuticular microbes. Stochastic processes appeared to be served as the primary drivers shaping the core microbial community structures. Cuticular dominant and functional microbial community assemblies except for Escherichia may be primarily driven by stochasticity to adapt the unstable habitats. The direct comparison of gut and cuticular microbiomes may provide valuable insights into the specific functions of symbiotic microbes, and offer critical molecular data for broader understanding of symbiotic relationship between bark beetles and microbes.