The tolerance of difenzoquat and diclofop‐methyl by winter wheat varieties at different growth stages

SUMMARY Winter wheat varieties were treated with the wild‐oat herbicides difenzoquat and diclofop‐methyl at several growth stages in a series of four field experiments. High rates of difenzoquat damaged the winter wheat varieties Bouquet, Sportsman, Hobbit and Maris Huntsman but not Hustler. Treatment of the sensitive varieties during tillering stimulated excessive tiller production, resulting in more ears with fewer and smaller grains than on the unsprayed controls; later applications reduced the number of grains and severely depressed yield. In contrast, the early applications of diclofop‐methyl, during tillering, were more damaging than the later ones. Bouquet was more tolerant of diclofop‐methyl than were the other varieties tested.