INFLUENCE OF HERBICIDES FOR BROAD-LEAVED WEEDS AND ADJUVANTS WITH DICHLORFOP METHYL ON WILD OAT CONTROL

Abstract

A reduced rate of dichlorfop methyl 2[4-(2,4-dichlorophenoxy)-phenoxypropionic acid methyl ester] (0.56 kg/ha) in combination with different adjuvants provided as effective wild oat (Avena fatua L.) control as the recommended field rate (1.12 kg/ha) without adjuvants. Barley (Hordeum vulgare L.) yields were higher when treated with dichlorfop methyl at 0.56 kg/ha plus adjuvants than when treated with dichlorfop methyl at 1.12 kg/ha. The herbicidal activity of dichlorfop methyl on wild oats was severely reduced on addition to the spray mixture of growth-hormone-type herbicides for broad-leaved weeds. The antagonism was due to the active ingredients in the herbicide formulations for broad-leaved weeds rather than to solvent incompatibilities. Ester formulations of herbicides for broad-leaved weeds caused less antagonism of dichlorfop methyl activity than did amine formulations. Non-hormonal contact-type herbicides (e.g., bromoxynil at 0.28 kg/ha) were compatible with dichlorfop methyl. Attempts to find a mixture containing low rates of dichlorfop methyl and extra adjuvants in combination with low rates of both bromoxynil and MCPA ester, which would be effective against both broad-leaved weeds and wild oats, were unsuccessful. Dichlorfop methyl did not reduce the herbicidal activity of growth-hormone-type herbicides on Tartary buckwheat (Fagopyrum tataricum L. Gaertn.).