Residues of Ethoprop and Disulfoton in Soils and Flue-cured Tobacco

Soil samples collected approximately 21 days after pretransplant applications of ethoprop to flue-cured tobacco land contained residues averaging 0.54 and 1.13 ppm, respectively, for the 6.7 and 13.4 kg/ha rates. In contrast total residues of disulfoton (disulfoton plus three metabolites) averaged 0.28 and 0.54 ppm at 3.4 and 6.7 kg/ha rates. Concentrations of both compounds decreased with time at each of two locations. Residue levels of ethoprop in the first harvest of flue-cured tobacco from the Central Crops Research Station (Clayton, North Carolina) were 0.04, 0.02, and 0.08 ppm; from the Upper Piedmont Research Station (Reidsville, North Carolina), residues were 0.20, 0.16, and 0.27 ppm, respectively, for rates of 6.7, 6.7 combination (with disulfoton), and 13.4 kg/ha. Residues declined in succeeding harvests. Total residues of disulfoton plus three metabolites in the first sample of tobacco harvested from Central Crops averaged 2.52 and 1.89 ppm; and from Upper Piedmont residues averaged 10.24 and 6.50 ppm, respectively, for rates of 3.4 and 6.7 kg/ha. The residues declined in succeeding harvest and were 0.14 ppm or less by the fourth harvest at Central Crops and 0.08 ppm or less by the fifth harvest at Upper Piedmont.