Abiotic and biotic degradation of dithiopyr in golf course greens

Results of previous research have indicated that only a small fraction of dithiopyr [S,S-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate] is lost in the surface water or by infiltration in soil leachate following application to golf course greens. The purpose of this research was to investigate the abiotic and biotic agents for dithiopyr loss from golf course greens. Growth chamber and laboratory studies were conducted to determine dithiopyr loss in response to volatilization, photodegradation, chemical transformation, and biological degradation in sterile and nonsterile rooting media (RM) and RM leachate collected from established golf course greens maintained in the greenhouse. Following application to RM, dithiopyr was lost primarily by volatilization which increased with increasing treatment period and temperature. The estimated half-life for dithiopyr in RM ranged from 68.8 days (sterile RM, dark, 20 degrees C) to 39.2 days (nonsterile RM, dark, 35 degrees C). Dithiopyr degradationin RM leachate was greater under UV radiation than in the dark and was faster than in distilled water under the same conditions indicating the potential for the presence of photosensitizers prompting photodegradation of dithiopyr in the RM leachate. The estimated half-lives for dithiopyr in RM leachate ranged from 515 days (sterile RM leachate, dark, 6.8 pH, 20 degrees C) to 0.8 days (nonsterile RM leachate, UV light, 6.8 pH, 20 degrees C). Results indicate a large effect of environmental variables on dithiopyr loss and its persistence in the turfgrass ecosystem.