Downy brome control in winter wheat is often inadequate. The effects of three crop rotations and two tillage intensities on downy brome populations and associated crop yields were determined in an experiment at Lethbridge, Alberta from 1987 to 1993. Downy brome densities in continuous winter wheat increased from 24 to 970 plants/m2 between 1988 and 1993; and were often higher with zero tillage. Inclusion of fallow or spring canola in rotation with winter wheat suppressed downy brome densities to less than 55 and 100 plants/m2, respectively, over the six years. In continuous winter wheat, yields decreased as downy brome densities increased progressively over years, indicating that monoculture winter wheat production will not be viable in regions where downy brome is prevalent unless effective herbicides are developed. In the more arid areas of the Canadian prairies, a winter wheat-fallow rotation may be most suitable but in higher precipitation areas, a winter wheat-canola rotation is a viable alternative. Crop rotation is a key component of an improved management system for control of downy brome.

Few postemergence (POST) herbicides are available for broad-spectrum weed control in pea. Field experiments were conducted to determine the suitability of imazamox to provide selective control of grass and broadleaf weeds in pea. Imazamox controlled several grass and broadleaf species, but the rate required to attain 90% control ranged from 7 to 36 g ai/ha depending on the weed species. Imazamox efficacy differed with the adjuvant included in the spray mixture. Merge adjuvant often increased imazamox activity on weeds more than Sun-It II methylated seed oil or a combination of Agral 90 adjuvant plus 28–0–0 liquid fertilizer. Pea exhibited excellent tolerance to imazamox up to the highest rate applied, 40 g/ha. Pea yield comparable to that of the hand-weeded control was attained with 20 to 30 g/ha of imazamox. Imazamox offers growers a POST option for broad-spectrum weed control in pea.