Residual Toxicity of Fensulfothion in Soil and Uptake of Toxic Residues by Rutabagas and Carrots During Wet and Dry Growing Seasons

In mineral loam soils of Prince Edward Island, a single preplanting application of fensulfothion was sufficiently persistent to give good to excellent control of root maggots attacking rutabagas throughout the growing season during 13 of the past 15 years. However, during two abnormally wet growing seasons (1977 and 1979), this compound gave little or no control. Bioassays indicated that toxic residues disappeared more quickly from field treated soil during these wet growing seasons, but that higher levels of toxicants were absorbed by rutabagas grown in the treated soil. Chemical residue analyses of soil and of carrots and rutabagas grown in microplots, where lateral movement of insecticide and plant development was restricted, showed that total residues of fensulfothion and fensulfothion sulfone were ca. 2.5, 8.5, and 20 times higher in the soil, carrots, and rutabagas, respectively, during the relatively dry growing season of 1978 than during the abnormally wet season of 1979.