Nematicidal activity of marcenmicin D2 from Fusarium sp. against Bursaphelenchus xylophilus

Abstract BACKGROUND Pine wilt disease (PWD) caused by Bursaphelenchus xylophilus is a devastating forest disease worldwide, and there is an urgent need for environmentally friendly biocontrol agents. Cyclic lipopeptides from microbial sources exhibit diverse biological activities, but their nematicidal potential against B. xylophilus remains largely unexplored. RESULTS A cyclic lipopeptide, marcenmicin D2, was isolated from the endophytic fungus Fusarium sp. SSY‐3. Marcenmicin D2 exhibited potent nematicidal activity against B. xylophilus in a concentration‐ and time‐dependent manner, with a median lethal concentration (LC 50 ) value of 41.6 mg L −1 at 24 h. At 50 mg L −1 , it achieved 100% mortality within 48 h and strongly inhibited egg hatching (>96% at 50 mg L −1 ). The compound rapidly reduced head swing frequency within 3 h, and induced unique morphological abnormalities including aggregation, irregular body bending, coiling and cuticle shrinkage, which were not observed in abamectin‐treated nematodes. In treated nematodes, the biochemical evidence of oxidative perturbation (changes in superoxide dismutase, catalase and malondialdehyde) and the transcriptomic signatures, notably the coordinated downregulation of cuticle‐related collagens, peroxisomal/lysosomal pathways, cytochrome P450‐dependent xenobiotic metabolism and carbohydrate metabolic genes, are consistent with the multifaceted nature of marcenmicin D2's activity against B. xylophilus . CONCLUSION Marcenmicin D2 is a potent cyclic lipopeptide nematicide from Fusarium sp. that acts through disruption of cuticle integrity, impairment of detoxification systems, interference with cellular degradation pathways, and induction of oxidative stress. Its rapid immobilization of B. xylophilus , mechanism distinct from that of abamectin and strong egg‐hatching inhibition make it a promising lead compound for sustainable PWD management. © 2026 Society of Chemical Industry.