The experiment was conducted during 3 yr to measure the effect of corn cockle (Agrostemma githago L.) competition on winter wheat (Triticum aestivum L. ‘McDermid’) grain yield. In all years corn cockle was removed monthly in separate treatments from emergence (October) to harvest (July). Hand-weeded and weedy controls were compared to herbicidal control using treatments of bromoxynil (3,5-dibromo-4-hydroxybenzonitrile). Reductions in yield of wheat as affected by competition from corn cockle were not significant if weeds were removed before February of each year in winter wheat that had been seeded the previous October. Bromoxynil controlled more weed plants when applied on corn cockle that had less than four leaves (fall treatment). Corn cockle densities of 170 to 340 plants/m2 at the Pendleton, Oregon site lowered wheat yields an average of 18% when competition was eliminated by March. Competition that continued until wheat harvest (July) reduced yields 60%.
