Competition of Blue Mustard with Winter Wheat

Winter wheat (Triticum aestivum L., var. Gaines) plots infested with seedling blue mustard (Chorispora tenella (Willd.) DC) were hand-weeded or treated in the fall with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) at 1 lb/A and 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) at ⅜ lb/A. Additional wheat plots were established in the fall with populations of one, three, and nine blue mustard seedlings per square foot, and the next spring these were either untreated, hand-weeded, or treated with (2,4-dichlorophenoxy)acetic acid (2,4-D) at 1 lb/A. All plots were harvested in July. Maximum wheat yields were obtained from plots hand-weeded or treated in the fall. Wheat production decreased significantly as weed population increased. Grain yield reduction, resulting from weed competition during the winter months, was significant and accounted for more than 50% of the total loss.