Nematicidal Activity of Fatty Acid Esters on Soybean Cyst and Root-knot Nematodes

Abstract

Researchers have indicated that the C₉ fatty acid, pelargonic acid (nonanoic acid), has considerable nematicidal activity that could be increased by derivitization and improved emulsification. Microemulsions of methyl and ethylene glycol esters of pelargonic acid developed by Mycogen Corporation (San Diego, CA) were tested for nematicidal activity against root-knot and soybean cyst nematodes. All treamaents were compared to a deionized water control and a microemulsion "blank" (minus active ingredient). Methyl pelargonate reduced gall numbers at concentrations ≥0.8 μl a.i./liter, and ethylene glycol pelargonate reduced gall numbers at ≥6.4 μl a.i./liter in a laboratory bioassay of Meloidogyne javanica on roots of tomato seedlings. Microscopic observation of treated M. javanica second-stage juveniles suggested that methyl pelargonate was toxic to nematodes at concentrations as low as 0.2 μl a.i./liter. Cysts of Heterodera glycines per gram of root were significantly reduced by weekly soil drenches of methyl pelargonate at 6.4, 3.2, and 1.6 μl a.i./liter compared to controls in one greenhouse experiment. Weekly soil drenches of methyl pelargonate at 4.8 or 3.2 μ1 a.i./liter also significantly reduced the number of eggs produced by M. incognita on soybean in a greenhouse test. In both greenhouse tests with soybean, rates of methyl pelargonate ≥4.8 μl a.i./liter had considerable phytotoxicity. No significant interaction of chemical treatment and different soil mixtures affected the nematode numbers produced or plant vigor observed. Soil drenches with microemulsions of methyl pelargonate at 3.2 μl a.i./liter applied weekly, or as two initial applications, were effective as a nematicide for root-knot and soybean cyst nematodes with negligible effects on plant vigor.

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