The influence of growth stage and foliage or soil application on the activity of AC 222,293 against Alopecurus myosuroides and Arena fatua

SUMMARY AC 222,293 was active against both Alopecurus myosuroides and Avena fatua following foliage or root entry. The most effective site of application was the foliage for A. fatua and the soil for A. myosuroides. In glasshouse and controlled environment studies, growth inhibition was transient with extensive subsequent regrowth occurring following applications at below recommended field doses. Performance declined when application was delayed until A. fatua had more than five and A. myosuroides more than six leaves. This lower activity could be only partly explained by lower spray retention and uptake of the herbicide, since there were no differences in either translocation from the treated laminae or metabolism to the biologically active free acid. Other factors that may have contributed to the reduced performance are discussed.