Bursaphelenchus xylophilus is killed by homologues of 2-(1-undecyloxy)-1-ethanol

2-(1-Undecyloxy)-1-ethanol, monochamol, is a male-produced aggregation pheromone of the Monochamus species, which are efficient vectors of the pine wood nematode (PWN), Bursaphelenchus xylophilus, which cause devastating damage to pines worldwide. The nematicidal activity of synthetic monochamol and its homologues (ROEtOH: R = C(7)-C(13)) were investigated to find potential alternatives to the currently used PWN control agents abamectin and emamectin. Compounds with C(7)-C(13) chain length alkyl groups exhibited 100% nematicidal activity at a concentration of 1000 mg/L. At a concentration of 100 mg/L, 2-(1-nonyloxy)-1-ethanol (C(9)OEtOH), 2-(1-decyloxy)-1-ethanol (C(10)OEtOH), 2-(1-undecyloxy)-1-ethanol (C(11)OEtOH), and 2-(1-dodecyloxy)-1-ethanol (C(12)OEtOH) showed 100% nematicidal activity, but the others showed weaker activities. C(11)OEtOH showed similar nematicidal activity to abamectin in terms of LD(90) values, which were 13.30 and 12.53 mg/L, respectively. However, C(9)OEtOH, C(10)OEtOH, and C(12)OEtOH (LC(90) values: 53.63, 38.18, and 46.68 mg/L, respectively) were less effective than C(11)OEtOH and abamectin. These results indicate that monochamol could be an effective alternative agent against PWN. The relationship of insecticidal and nematicidal activity to different carbon chain lengths in compounds is discussed.