Quantification and remediation of pesticides in runoff water from containerized plant production

During containerized plant production pesticides may move from application site in runoff water created by overhead irrigation systems. In this study, four pesticides, isoxaben (N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide), trifluralin ((2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate) and thiophanate-methyl (dimethyl 4,4'-o-phenylene bis(3-thioallophanate), were applied at a commercial plant nursery. Overhead irrigation after application generated runoff water which was channeled into waterways of clay/gravel or hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy]. Isoxaben was detected in runoff water through 4 d after application (DAA). Other pesticides were detected primarily on the day of application (DOA). Thirteen percent of applied thiophanate-methyl was recovered from the clay/gravel waterway and 11% front the grass waterway. Total amounts of isoxaben lost were 23% of total applied in both treatments. Less than 0.01% of applied chlorpyrifos and trifluralin were detected. Isoxaben amounts recovered front the grassed waterway on the DOA were 16% lower than from the clay/gravel treatment. Thiophanate-methyl amounts were 18% lower from the grassed treatment on the DOA. The results suggest that vegetated waterways can reduce pesticide losses from application site in runoff water.