Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/18/2007
Publication Date: 3/1/2008
Citation: Meyer, S.L., Lakshman, D.K., Zasada, I.A., Vinyard, B.T., Chitwood, D.J. 2008. Dose-response effects of clove oil from Syzygium aromaticum on the root-knot nematode Meloidogyne incognita. Pest Management Science. 64:223-229. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause ten billion dollars in U.S. crop losses annually. Root-knot nematodes are among the most destructive species. One problem facing growers is the lack of safe and effective methods for controlling nematode-induced crop losses. Because of this need for new management agents, the natural substance clove oil was tested for toxicity to the root-knot nematode. The study demonstrated that levels of clove oil up to 0.4% were needed to substantially decrease egg hatch and to completely kill already-hatched nematodes. A clove oil concentration of about 0.12% was required to kill half of all eggs and hatched nematodes. The results are significant because they demonstrate that this essential oil has potential use as a nematicidal natural product. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: BACKGROUND: Clove oil, derived from the plant Syzygium aromaticum (L.) Merr. & Perry, is active against various organisms, and was prepared in a soy lecithin/detergent formulation to determine concentrations active against the root-knot nematode Meloidogyne incognita (Kofoid and White) Chitwood. RESULTS: In microwell assays, the mean effective clove oil concentration that reduced egg hatch by 50% (EC50) was 0.097% (v/v) clove oil; the EC50 for second-stage juvenile (J2) viability was 0.145% clove oil (compared withcarrier control treatments). Volatiles from 5.0% clove oil reduced nematode egg hatch in water by 30%, and decreased viability of hatched J2 by as much as 100%. Reductions were not as large with nematodes in carrier. In soil trials with J2 recovered from Baermann funnels, the EC50 = 0.192% clove oil (compared with water controls). CONCLUSION: The results demonstrated that the tested formulation is active against M. incognita eggs and J2, that the EC50 values for J2 in the microwell studies and the soil recovery tests were similar to each other and that direct contact with the clove oil is needed for optimal management results with this natural product.