NEMATOCIDAL ACTIVITY OF FATTY-ACID ESTERS ON SOYBEAN CYST AND ROOT-KNOT NEMATODES

Researchers have indicated that the C-g fatty acid, pelargonic acid (n onanoic acid), has considerable nematicidal activity that could be inc reased by derivitization and improved emulsification. Microemulsions o f methyl and ethylene glycol esters of pelargonic acid developed by My cogen Corporation (San Diego, CA) were tested for nematicidal activity against root-knot and soybean cyst nematodes. All treatments were com pared to a deionized water control and a microemulsion ''blank'' (minu s active ingredient). Methyl pelargonate reduced gall numbers at conce ntrations greater than or equal to 0.8 mu l a.i./liter, and ethylene g lycol pelargonate reduced gall numbers at greater than or equal to 6.4 pi a.i./liter in a laboratory bioassay of Meloidogyne javanica on roo ts 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 mu l a.i./liter. Cysts of H eterodera glycines per gram of root were significantly reduced by week ly soil drenches of methyl pelargonate at 6.4, 3.2, and 1.6 mu l a.i./ liter compared to controls in one greenhouse experiment. Weekly soil d renches of methyl pelargonate at 4.8 or 3.2 mu l a.i./liter also signi ficantly reduced the number of eggs produced by M. incognita on soybea n in a greenhouse test. In both greenhouse tests with soybean, rates o f methyl pelargonate greater than or equal to 4.8 mu l a.i./liter had considerable phytotoxicity. No significant interaction of chemical tre atment and different soil mixtures affected the nematode numbers produ ced or plant vigor observed. Soil drenches with microemulsions of meth yl pelargonate at 3.2 mu l a.i./liter applied weekly, or as two initia l applications, were effective as a nematicide for root-knot and soybe an cyst nematodes with negligible effects on plant vigor.