What can you spray to get rid of winter annual weeds like wild oats, cheatgrass, and downy brome?
Before deciding to spray, first you must realize that seed of these grasses lasts several years in the soil. That means you need to plan to repeat any spraying for at least a couple years.
In pastures dominated by warm-season grasses, one option is to spray 1 pint per acre of glyphosate, like Roundup, early this spring after the weedy bromes green up but before warm-season grasses start growing. This should solve the problem for this year and knock out other early weeds like bluegrass without harming your warm-season grasses. Another option is to use 4 to 6 ounces of Plateau herbicide and get similar results. And with Plateau, residual herbicide activity also will control some later emerging weeds as well.
If your pasture is cool-season grass the job is tougher. Both glyphosate and Plateau harm cool-season grasses. Gramoxone is a better choice but don't spray until the weedy bromes are about to form seed heads. Gramoxone will kill all the green top growth it comes in contact with, even your good grass. But your good perennial grasses will start to regrow after a couple of weeks while the weedy grasses will be killed, eliminating their seed production this year.
Once you’ve gotten rid of the weeds, be sure to graze in ways that maintain the vigor and competitiveness of your desired grasses.
Winter annual bromes reduce pasture quality and carrying capacity. Herbicides, and proper grazing, can control them if you use them right.