Nematicidal activity of monoterpenoid compounds against economically important nematodes in agriculture

The phase-out of increasing numbers of synthetic nematicides has prompted an urgent need for environmentally benign and effective products to protect crops from nematode damage. We tested a group of selected plant-origin monoterpenoid compounds for their nematicidal activities, and found some of them could be potent nematicides. Most of the monoterpenoids were more toxic than the commercial nematicide oxamyl (13.4% mortality at 250 mu g/mL) against the soil saprophytic nematode Caenorhabditis elegans, among which carvacrol and thymol were the most potent (100% mortality at 250 mu g/mL). (-)-Perillaldehyde, eugenol, geraniol and menthol were of moderate nematicidal activity at the same concentration, with mortality at 97%, 91%, 90% and 84%, respectively, against C. elegans. Nematicidal activity against the root lesion nematodes Pratylenchus penetrans was generally less potent, but citronellol, carvacrol and (-)-perillaldehyde were more toxic (mortality at 250 mu g/mL were 87%, 78% and 56%, respectively) than oxamyl (50%). Thymol showed similar (50%) mortality to that of oxamyl.