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.