The Control of Grasses with Sodium TCA and Dalapon1

Abstract

Grasses are a major weed problem in both cultivated and uncultivated areas. In Thailand, paragrass (Brachiariamutica), torpedograss (Panicum ripens) and lalang (Imperata cylindrical) are the most widespread and difficult to control among the perennial grasses. Torpedograss and lalang have deep rhizomes, while paragrass has relatively shallow stolons and culms (Fig. 1-3) The first effective selective herbicide for grasses to appear was sodium trichloroacetate, commonly designated as TCA (McCall and Zahnley, 1949). Through the substitution of one of the chlorine atoms in TCA with a methyl group another effective herbicide, 2,2-dichloropropionic acid (dalapon) was produced (Dow-Chemical Co., 1953). Both of these chemicals have been demonstrated to be highly effective against Johnsongrass (Sorghum halepense) Burmudagrass (Cynodon dactylon), quack grass (Agropyron repens), and others (Audus, 1964 : Hanson, 1956).