Tips for downy brome control
Downy brome usually begins growing in the fall or early spring. Reproduction is by seed and seedling plants must be vernalized to produce seed. In medium-textured soils, the optimum seed depth for downy brome emergence is less than 1 inch; however, seedlings have emerged from a 4-inch depth in western Nebraska. The plant tillers profusely, depending on time of germination. In early spring the plant continues to tiller, joints, and sets seed (see Figure 1). The plant grows from 6 to 24 inches tall. Height depends on available soil water, fertility, and plant competition. At emergence, leaves are about 1/32 of an inch wide and brownish-green. As the plant and seed reach maturity, leaves turn purplish-tan.
- Leaves — Leaf blades are flat and 2 to 6 inches long. Blades and sheath are hairy.
- Ligule — Prominent membrane with frayed margin to almost 0.10 inch long.
- Auricle — None
- Roots — Fibrous and relatively shallow.
- Stems — Smooth, slender, and erect, protruding from a much-branched base.
- Panicle and seed — Panicles are 2 to 6 inches long, slender, and dropping to one side. Spikelets are numerous, five to eight flowers with slender straight awns, 1/2 to 3/4 inch long, each attached to a hairy, buff-brown, narrow seed about 1/2 inch long. The seeds are light and fluffy — about 200,000 per pound. Initial seed germination rates usually are high. A heavy infestation can produce as much as 400 lbs or 80 million seeds per acre. Some seeds will remain viable more than two years when placed near the soil surface because of natural dormancy or unfavorable conditions for germination.
Downy brome is best managed by integrating cultural and chemical control measures to eliminate seed sources, contain its spread, and kill existing weeds before they can compete with crops and pastures for water resources. Crop rotation is one of the most effective control measures; however, this is not a viable option in pastures or in some cropping systems in western Nebraska. The following sections describe two control options — eliminating seed sources and rotating crops — as well as strategies best suited to specific cropping systems.
Eliminating Seed Sources Outside the Fields
- Till and crop roadside ditches when possible or seed to a perennial grass.
- Seed perennial, cool-season grasses such as crested wheatgrass or smooth brome in waste areas and field borders. Vigorous stands of grasses or grass-legume combinations are highly competitive with downy brome and other annual weeds. See section on Reestablishing Desirable Grasses in Waste Areas for additional information.
- Sometimes mowing can be effective in reducing seed production, but it will not eliminate downy brome. Mowing must be timely and close to the ground. More than one mowing may be necessary to prevent tillers from producing seed. Mowing is useful for small infestations in pastures, roadsides, and waste areas where cultivation or herbicides are not feasible. Mowing also may reduce competition so that desirable perennial grass may reestablish.
- On cultivated fields, destroy weeds before they produce seed.
- Plant clean seed. Downy brome seeds often are found in small grain and grass seed.
- Use herbicides that do not kill established perennial grasses around field borders.
- Control small patches or area infestations before they spread.