INTERACTION BETWEEN DIFENZOQUAT AND PROPANIL OR PROPANIL/MCPA COMBINATIONS FOR WILD OAT AND GREEN FOXTAIL CONTROL IN BARLEY

Abstract

Tank mixtures of difenzoquat and propanil or propanil/MCPA were evaluated for the control of wild oats (Avena factua L.) and green foxtail (Setaria viridis (L.) Beauv.) in a single spray operation. Both propanil and propanil/MCPA reduced the efficacy of difenzoquat on wild oats, but the efficacy of propanil or propanil/MCPA on green foxtail was not adversely affected. Barley (Hordeum vulgare L.) tolerance to the tank mixture was lower than to either of the components of the mixture. Uptake of 14C-difenzoquat by wild oats was reduced markedly in the presense of propanil and propanil/MCPA. If the herbicides were applied separately, the reduction in uptake depended on the extent of overlap of droplets of the two spray preparations on the leaf surface. There was no evidence of a chemical change in difenzoquat in the tank mixes, but the observed separation of components of the mixture soon after mixing may be partly responsible for the reduced uptake. We conclude that the marked inhibition of difenzoquat uptake in the presence of propanil or propanil/MCPA plays an important role in bringing about the antagonism between these herbicides.