Downward migration of trichlorfon insecticide in turfgrass soils

The downward migration of the insecticide, trichlorfon (o,o-dimethyl-2,2,2-trichloro-l-hydroxyethylphosphonate) was studied in a fine sandy loam, a silt loam and a sand each prepared in lysimeter plots and seeded with creeping bentgrass. The extent of insecticide leaching was determined as a function of interval after trichlorfon application under two irrigation regimes simulating above or below average precipitation. Trichlorfon moved downward quite rapidly with traces still detectable in leachates 23 days following application. The percentages of total applied insecticide recovered in the leachates were in the range of 1 and 4 percent at the lower and higher rates of irrigation, respectively. Factors affecting the various modes of dissipation of trichlorfon are discussed.