Nematicidal Activity of Alkyloxyalkanols Against Bursaphelenchus xylophilus

Pine wilt disease, caused by the pine wood nematode Bursaphelenchus xylophilus (Steiner & Bührer) Nickle, poses a major threat to pine forests worldwide. While avermectin-based pesticides are currently used for pine wilt disease management, alternative approaches are needed to mitigate the risk of resistance. This study evaluated the nematicidal activity of 24 synthetic alkyloxyalkanols (ROR′OH) against B. xylophilus. The compounds were synthesized by the etherification of diols with 1-bromoalkanes and tested in a microplate bioassay. Mortality was measured after 24 h, and LD50 values were calculated. Several compounds, including 2-(1-decyloxyl)-1-ethanol (C10OC2OH) and 8-(1-hexyloxy)-1-octanol (C6OC8OH), showed potent nematicidal effects, with LD50 values of less than 50 ppm. Structure–activity relationship analysis revealed that compounds with chains containing an even number of carbons in both the alkyl and alkyloxy groups tended to exhibit increased activity. Clustering analysis confirmed that carbon parity significantly affected efficacy (Mann–Whitney U = 15, p < 0.001). Compared with previously reported plant-derived compounds, several of these alkyloxyalkanols demonstrated superior potency. The results suggest that odd–even carbon chain parity, a known physicochemical phenomenon of n-alkanes, may underlie variations in nematicidal activity. These findings provide insight into the design of novel nematicides targeting B. xylophilus.