Field experiments were conducted to select winter wheat (Triticum aestivumL.) cultivar(s) that were competitive to downy brome (Bromus tectorumL. # BROTE). Downy brome significantly reduced winter wheat grain yields of all cultivars by 9 to 21% at Lincoln, while at North Platte yield reduction ranged from 20 to 41% depending upon cultivar. ‘Turkey’ was the most competitive cultivar to downy brome but it had the lowest grain yield. Compared to ‘Centurk 78’, ‘Centura’ at Lincoln and ‘SD 75284’ at North Platte proved to be significantly higher yielding and more competitive to downy brome. Winter wheat tiller number, canopy diameter, and plant height were negatively correlated with downy brome yield, but changes in these growth parameters did not always translate into grain yield advantage in downy brome-infested plots. Based on stepwise regression analysis, wheat height was better correlated with reduction in downy brome yield than were canopy diameter or number of tillers.

Differences in weed interference among winter wheat (Triticum aestivumL.) cultivars have been observed in farmer fields. Identifying cultivars that are more competitive would be useful in weed control programs. Twenty cultivars of winter wheat were grown with spring germinating weeds during 1979 and 1980 and eight cultivars were grown in 1981 at North Platte, NE on a Typic Argiustoll soil. Cultivars included semi‐dwarf through normal statured types and were adapted to a wide geographic area of the Central Great Plains. ‘Lancota’ selections (NE 78939, NE 78906, NE 78895, NE 78892, and NE 78925) and sister lines NE 78742 and NE 78743 were good weed competitors. ‘Centurk 78’, ‘Buckskin’, ‘Vona’, and ‘Sage’ were intermediate, while ‘Homestead’ and several lines with Homestead germplasm were relatively poor annual weed competitors. Several cultivars that were 73 to 78 cm tall were poor competitors with weeds, while most cultivars that were 83 cm or taller were good competitors. NE 78742 (75 cm) and NE 78743 (72 cm) were among the shortest cultivars but were among the best in competitiveness with weeds. Cultivar selection can reduce summer annual weed growth in winter wheat