THE EFFECT OF PLACEMENT AND CONCENTRATION OF 2,3-DCDT ON THE SELECTIVE CONTROL OF WILD OATS IN WHEAT

A series of experiments on different soils and with varying concentrations demonstrated that the herbicidal activity of 2,3-DCDT (2,3-dichloroallyl diisopropylthiolcarbamate3) is primarily via the coleoptile rather than the root system of wild oats and wheat. The degree of this activity differed between the two species depending on the stage of development when they came in contact with treated soil, the concentration of the herbicide and the length of time that the coleoptile was in contact with treated soil. In wild oats there were two distinct periods of high sensitivity, namely, during the initial half-inch of coleoptile growth and a later stage which appeared to coincide with the initiation of the crown node. Wheat was highly sensitive at only the early period. This crop was tolerant to sufficiently high concentrations of 2,3-DCDT, when planted at least a half-inch below a surface layer of treated soil, to permit the selective control of wild oats in wheat. However, the relative placements were critical. The pattern of response was similar in each of the soils but the degree of response was distinctly higher on the heavy clay than on the loam soils.