CONTROL OF DOWNY BROME (BROMUS-TECTORUM) WITH HERBICIDES AND PERENNIAL GRASS COMPETITION

Long-term control of downy brome with an integrated approach is needed in order to sustain range productivity. Studies were conducted to stu dy the effectiveness of a combination of downy brome control practices . In two studies, glyphosate and paraquat were evaluated at various ra tes for up to three successive years for control of downy brome in ran geland. A third study evaluated the competitiveness of perennial cool- season grasses against downy brome in the absence of herbicides. Glyph osate, at 0.55 kg/ha, and 0.6 kg/ha paraquat provided selective downy brome control on rangeland when applications were combined with intens ive grazing. Downy brome control was greater than 90% following two se quential years of 0.6 kg/ha paraquat at either the two- to eight-leaf stage or bloom stage at both study locations. At one study location, 0 .55 kg/ha glyphosate provided 97% control after the first application at both growth stages. In the second study, control averaged greater t han 92% following three sequential applications of glyphosate. When pe rennial cool-season grasses were seeded in the spring following fall t illage (no herbicides) and allowed to establish for three growing seas ons, three of the five species were effective in reducing the reestabl ishment of downy brome. 'Luna' pubescent wheatgrass, 'Hycrest' crested wheatgrass, 'Sodar' streambank wheatgrass, 'Bozoisky' Russian wildrye , and 'Critana' thickspike wheatgrass controlled 100, 91, 85, 45, and 32% of the downy brome, respectively. Yields of perennial grass dry ma tter were 1,714, 1,596, 1,135, 900, and 792 kg/ha. Replacing noncompet itive annual grasses with competitive cool-season perennials will prov ide a longer term solution to a downy brome problem than the use of he rbicides alone or with intensive grazing.