Persistence of 5,6-Dichloro-2-trifluoromethylbenzimidazole, a Major Degradation Product of Fenazaflor, in Hagerstown Silt Loam Soil1

Abstract

Persistence of 5,6-dichloro-2-trifluoromethylbenzimidazole (NC-2983), a major degradation product of the new acaricide, fenazaflor, in Hagerstown silt loam soil was studied by applying commercial formulations (Lovozal®) at different rates in single and repeat applications to field plots in the fall and in summer. Soil samples from different depths were analyzed at various intervals for residues of NC-2983 by gas chromatography. No significant disappearance of NC-2983 occurred from field soils during the autumn, winter, and early spring. The amount of NC-2983 in the soil, however, declined rapidly during the summer. Approximately 80% of the amount applied in the summer of 1971 disappeared in 135 days after application, whereas about one year was required for a comparable amount to disappear when similar amounts were applied in the autumn. Residues of NC-2983 were not found beyond the 6-inch depth in field plots. NC-2983 was not found in the peel-free portions of potatoes, and only trace amounts were found in the peel-free parts of carrots. Significant amounts of NC-2983 were found in the peel of both crops, especially at the highest rate of application.