Selectivity and mode of action of ethyl (±)-2-(N-benzoyl-3,4-dichloroamiino)propionate in the control of Arena fatua in cereals

The activity of foliar applications of ethyl (±)-2-(N-benzoyl-3,4-dichloroanilino)—propionate(benzoylprop-ethyl)to oat was dependent upon its degradation to the biologically active acid (benzoylprop). The acid, unlike benzoylprop-ethyl, showed some movement via the phloem from the foliage to the stem where it inhibited stem elongation through an effect on cell expansion. The resulting stunted wild plants oat were unable to compete successfully with the cereal crop. Selectivity of the herbicide was dependent on its relative rate of de-esterification, and the subsequent detoxication of the acid to inactive conjugates. De-esterification was fastest in oat and slowest in wheat. The rate of detoxication in wheat prevented the accumulation of the acid to phytotoxic levels but in oat, although the rate of detoxication was higher, it failed to prevent the occurrence of phytotoxic levels of benzoylprop. In barley de-esterification was slower than in oat, and detoxication again failed to prevent some accumulation of the acid.