Mobility and Persistence of Pesticides Applied to a USGA Green. III: Organophosphate Recovery in Clippings, Thatch, Soil, and Percolate
- J. L. Cisar and
- G. H. Snyder
The general public is concerned about potential environmental in pacts of agrochemicals applied to turfgrass. It is especially important that certain industry standard turfgrass systems, such as USGA greens, be evaluated for potential environmental impact. The objective of this study was to assess the mobility and persistence of chlorpyrifos (O,O-diethyl-O-3,5,6-trichloro-2-pyridylphosphorothioate),isazophos [O-[5-chloro-1-(methylethyl)-lH-l,2,4-triazol-3yl] O,O-diethyl phosphorothioate], isofenphos [1-methylethyl 2-[[ethoxy(1-methylethyl) amino] phosphinothioyl]oxy] benzoate], and ethoprop (O-ethyl S,S-dipropylphosphorodithioate) applied to a USGA cv. Tifdwarf bermudagrass (Cynodon dactylon × C. transvaalensis Burtt-Davy) green. The quantity of each organophosphate (OP) pesticide in turf clippings, thatch, soil, and percolate was determined over two application cycles, with the exception of ethoprop which was applied once. Pesticide recovery in clippings after a single application of fenamiphos (ethyl 3-methyl-4(methylthio)phenyl (1-methylethyl)phosphoramidate) and fonofos (O-ethyl-S-phenyl ethylphosphonodithioate) was determined, in addition to the above mentioned OP pesticides. For liquid formulations, less than 1% of the OP pesticides applied were found in clippings. However, nearly 8% of chlorpyrifos and 1.2% of fonofos was removed in clippings after a granular application. Total average pesticide removed in clippings after granular applications of ethoprop, chlorpyrifos, fenamiphos, and fonofos were 9.9, 9.2, 5.1, and 4.3 mg m−2, respectively, while the largest amount from a liquid application of pesticide removed in clippings was 2.0 mg m−2 of isofenphos. Less than 0.1% of the OP pesticides applied to the USGA green were recovered in percolate water, regardless of substantial variations in rainfall and total percolation. Most of the applied OP pesticides appeared to be retained in the thatch layer, where presumably they were microbially degraded over time.
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