Short-chain fatty acids can be produced under anaerobic conditions by fermentative soil microbes and have nematicidal properties. We evaluated the effects of butyric and propionic acids on death and recovery of stunt nematodes (Tylenchorhynchus spp.), a common parasite of turfgrass. Nematodes in a sand-soil mix (80:20) were treated with butyric or propionic acid and incubated under air or N for 7 days at 25 degrees C. Amendment of soil with 0.1 and 1.0 micromol (8.8 and 88 microg) butyric acid/g soil or 1.0 micromol (74 microg) propionic acid/g soil resulted in the death of all nematodes. The composition of the soil atmosphere had no effect on the nematicidal activity of the acids. Addition of hydrochloric acid to adjust soil pH to 4.4 and 3.5 resulted in nematode mortality relative to controls (41% to 86%) but to a lesser degree than short-chain fatty acids at the same pH. Nematodes did not recover after a 28-day period following addition of 10 micromol butyric acid/g soil under air or N. Carbon mineralization decreased during this period, whereas levels of inorganic N and microbial biomass-N remained constant. Short-chain fatty acids appear to be effective in killing Tylenchorhynchus spp. independent of atmospheric composition. Nematode mortality appears to be a function of the type and concentration of fatty acid and soil pH.

The effects of butyric acid were evaluated on fungal and nematode endo-parasites of strawberries under controlled laboratory conditions. Verticillium dahliae, Rhizoctonia fragariae, R. solani, Phytophthora fragariae, and a Pythium sp. were killed after a 2-d incubation in butryic acid-treated sand (0.88 and 8.8mg g−1). No fungal growth occurred in the presence of vapors from 0.1 and 1 M butyric acid solutions. Gall formation on tomato roots by Meloidogyne hapla, and M. incognita was reduced by 73–100% relative to controls when egg masses were incubated in butyric acid solution (0.1, 1 M) or treated sand (0.88 and 8.8mg g−1). Drenching strawberry plants infested with Pratylenchus penetrans with butyric acid (0.1 and 1 M) reduced nematode densities by 98–100%. These results suggest that butyric acid warrants further evaluation as an alternative to synthetic soil fumigants for control of nematodes and fungal pathogens in strawberry.

Butyric acid, which is produced through fermentation of organic matter by anaerobic soil bacteria, possesses nematicidal properties. We investigated how the concentration of butyric acid in solution and gas phase affected the survival of 12 nematode species from four trophic groups. Our hypothesis was that survival of free-living and plant parasitic nematodes would differ, since free-living nematodes have shown some adaptation to survival in anaerobic soil environments.A 2-day incubation in sand amended with 0.88 mg butyric acid g(-1) reduced plant parasitic and fungivorous nematodes by 84-100% as compared to untreated controls, whereas a concentration of 8.8 mg butyric acid g(-1) was necessary to significantly reduce bacterivorous nematodes (70-98%). Sensitivity of entomogenous nematodes was variable, with Heterorhabditis adversely affected by 0.88 mg butyric acid g(-1) sand, resulting in a 59% reduction, while Steinernema required a concentration C sand to see a significant decline (85%). Results were similar when nematodes were exposed to the of 8.8 mg butyric acid g(-1) gas phase of butyric acid for 7 days. The vapor from a 0.1 M solution reduced plant-parasitic and fungivorous nematodes by 89-96% while the vapor from a 1 M solution of butyric acid reduced entomogenous nematodes by 94-99%. Bacterivorous nematodes did not survive the 7-day incubation period in appreciable numbers in either controls or treated sand. A 2-day incubation of nematodes in sand acidified with HCl to achieve pH values of 3.4 and 3.0 (similar to sand amended with 0.88 and 8.8 mg butyric acid g(-1) sand) had no effect on nematode survival in any of the trophic groups tested. A positive correlation was found between LC50 values for butyric acid and nematode surface area-to-volume ratios for four out of five plant parasitic nematodes (r = 0.99; P = 0.01) and a negative correlation was found for bacterivorous, entomogenous and fungivorous nematodes combined (r = -0.77; P = 0.07). The differentiation in chemical tolerances demonstrated here may hold a key to targeting plant parasitic nematodes without affecting free-living forms. (C) 2004 Elsevier B.V. All rights reserved.

A construct containing a rice chitinase gene and an alfalfa glucanase gene was co-transferred with a construct containing a bar gene as a selectable marker into creeping bentgrass using microprojectile bombardment. PCR analysis confirmed the presence of bar in the genomic DNA of transformed plants. Most of the transgenic plants were consistently resistant to 0.5–4.0% Finale® (a commercial brand of herbicide glufosinate, ammonium salt of phosphinothricin). The integration of the chitinase and glucanase genes into genomes of eight lines and the bar gene into all tested lines was confirmed by Southern hybridization analyses. Northern hybridization analyses indicated that the bar gene was transcribed in 15 transgenic lines at the mRNA level and that the chitinase gene was transcribed in 5 transgenic lines, but no glucanase mRNA was detectable. The frequency of the linked co-transfer of chitinase and glucanase genes was 100%, and the frequency of the unlinked co-transfer of the bar and chitinase/glucanase genes was 50–79%. The glufosinate-resistant transgenic lines exhibited resistance to fungal pathogens, Sclerotinia homoeocarpa and Rhizoctonia solani, when 0.5% Finale® was sprayed 3 h before the pathogen inoculation. When no Finale® was applied, the five transgenic lines expressing the chitinase gene were not resistant to the pathogens.

The effect of amending soil held at 3 different moisture levels with glucose, unsulfured molasses, or nutrient broth (0.3, 0.7, 3.2, 7.1 g carbon/100 g) on Tylenchorhynchus claytoni and T. dubius was investigated. When soil was held under saturated or flooded conditions in the absence of carbon amendments for 7 days, Tylenchorhynchus populations were 19% and 16%, respectively, of the controls. Carbon amendments at all levels tested precipitated a further decline in the nematode population to 1% or less of the unamended controls in 7 days. Two applications of molasses (7.4%, w/w) 3 days apart to nematode-infested soil held in Conetainers under mist for 7 days reduced Tylenchorhynchus spp. and Hoplolaimus galeatus densities to 7% and 3%, respectively, of the controls. Nematode densities in turfgrass field plots also declined following irrigation and repeated drenching with a molasses solution. Based on the observed decline in redox potential and pH in saturated soil, especially following carbon amendment, we propose that the activity of anaerobic fermentative bacteria was responsible for the reduction in nematode densities.