MOBILITY AND BIOACTIVITY OF THIOBENCARB

Laboratory and greenhouse studies were conducted to determine the mobility and bioactivity of thiobencarb on a Pahokee muck, Everglades muck, and Immokalee sand. On all soils > 93% of thiobencarb remained in the upper 1 cm after leaching during unsaturated flow. During saturated flow the retardation factor (R(T)) of thiobencarb on an Immokalee sand was 68, 20, 2, and 1 with 0, 25, 50, and 75% by volume methanol in 0.01 N CaCl2, respectively. There was a significant log-linear relationship (r2 = 0.97) between the Freundlich adsorption values (K(f)) estimated from R(T) values and the percentage by volume methanol of the leachate. In general, thiobencarb in combination with overhead irrigation reduced lettuce vigor and plant dry weight on an Immokalee sand more than with subsurface irrigation.