The red turpentine beetle Dendroctonus valens is an invasive forest pest that has been rapidly spreading northward since its introduction in China. Some ophiostomatalean associates of D. valens are essential contributing factors for this beetle to become an aggressive pine killer in China. In this study, a survey was conducted in a new invasive area of this beetle’s habitat in Liaoning Province. A total of 126 ophiostomatalean fungal associates of D. valens were isolated. Based on the combination of morphological characteristics and phylogeny, these isolates were identified as Ceratocystiopsis jianpingensis sp. nov., along with two new records, Leptographium terebrantis and Ophiostoma gilletteae. Ophiostoma gilletteae was the dominant species, with an isolation rate of 85.7%. The results of this study show that more shared ophiostomatalean fungi are associated with D. valens in China and North America, and accumulate resources for the development of fungal associate-mediated bark beetle management strategies.

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.

This study aimed to develop biofumigation strategies against chestnut fruit rot caused by Botryosphaeria dothidea. An endophytic strain, FPYF2509, was isolated from Castanea mollissima fruit and identified as Trichoderma nordicum using morphological and phylogenetic (tef1, rpb2) analyses. Antifungal volatile organic compounds (VOCs) were analyzed using headspace solid-phase microextraction and gas chromatography–mass spectrometry during dual-culture interactions with pathogens. The volatiles from the interaction exhibited to inhibit pathogen growth. Particularly an induced myrtenol, demonstrated strongly biofumigation activity in vitro, with a lowest observed effect concentration of 0.02 µL/mL, minimum inhibitory concentration and a minimum fungicidal concentration of 0.2 µL/mL against B. dothidea. In vivo, fumigation with 0.2 µL/mL myrtenol significantly reduced disease incidence from 83.3% to 17.39%, achieving a 79.1% control efficacy. This work presents endophytic T. nordicum FPYF2509 as a promising biocontrol agent and identifies myrtenol, of fungal interaction origin, as a novel and effective mycofumigant for postharvest disease management.

Leptographium procerum as a symbiotic fungus of Dendroctonus valens contributes significantly to pine decline and wood degradation in Pinus tabuliformis, yet effective and environmentally friendly management options remain limited. To explore biological control alternatives, we isolated endophytic bacteria from surface-sterilized healthy tissues of P. tabuliformis and identified them at the genus level by 16S rRNA gene sequencing. From 155 obtained strains, we screened for antagonistic activity against L. procerum, along with chitinase, siderophore, and IAA production, and selected Bacillus sp. strain Bt18 and Bacillus sp. strain Bm20 as the most promising candidates. When applied as a consortium to seedlings, the two strains significantly promoted growth, increasing root length by 48.2%, fresh weight by 57.9%–74.3%, and dry weight by 63.4%–80.0% relative to controls. Moreover, consortium-treated seedlings remained symptomless after pathogen inoculation, whereas control seedlings developed necrotic lesions averaging 2.41 cm². Time-dependent increases in catalase, polyphenol oxidase, phenylalanine ammonia-lyase, and superoxide dismutase activities indicated that the consortium induced systemic resistance. These results show that P. tabuliformis harbors diverse beneficial endophytes, and the Bt18–Bm20 consortium offers a promising, green strategy for managing blue-stain disease in pine forests.