Pine wilt disease, caused by Bursaphelenchus xylophilus (Steiner & Buhrer, 1934) Nickle 1981, poses a significant threat to the safety of pine forests in the world. Currently, the available nematicides for controlling this disease are limited. Finding new nematicides is crucial for the effective prevention and control of pine wilt disease. In this study, we discovered that tetramycin B₃, derived from Streptomyces ahygroscopicus, demonstrated a promising effect on pine wilt disease. The LC₅₀ values of tetramycin B₃ at 24, 48, and 72 h were 26.49, 23.37, and 12.79 μg/mL, respectively. Tetramycin B₃ significantly inhibited the feeding and growth rate of B. xylophilus at low concentrations while also increasing ROS (reactive oxygen species) production and lipid accumulation. Furthermore, tetramycin B₃ markedly inhibited the activity of detoxifying and protective enzymes. Transcriptome and metabolome analyses indicated that tetramycin B₃ significantly affected the expression of genes related to lysosomes, autophagy, and lipid metabolism in B. xylophilus. Additionally, tetramycin B₃ delayed the onset of pine wilt disease. Transcriptome results showed that tetramycin B₃ significantly influenced the expression of genes related to defense responses in pine trees and induced pine trees to produce disease-resistant mechanisms. Future research will focus on further elucidating the mechanism of action of tetramycin B₃ against B. xylophilus and verifying the gene functions identified through transcriptome screening.

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.