Controlling Winter Annual Bromes

Controlling Winter Annual Bromes

September 14, 2007

Winter annual bromes like downy brome, cheatgrass and wild oats often invade thin or overgrazed pastures in fall and early spring. Livestock dislike grazing them so over time they can make large patches of pasture nearly worthless.

Weed control to regain these pasture areas will take a multi-year commitment. If used correctly, in warm-season grass pastures and rangeland, Plateau and glyphosate herbicides can kill these annual bromes without harming the desirable grasses; however, no herbicides will control annual bromes in cool-season pastures without also injuring or killing the pasture grasses.

If annual brome density in not too thick and some desirable cool-season grass remains, sometimes an application of Gramoxone in November can be beneficial. This will kill annual bromes, but also may injure desirable grasses. Unfortunately, annual bromes that emerge next spring will not be affected.

If annual brome density is light, grazing and fertilizer management that strengthens desirable grasses may revive pasture productivity; however, if many annual bromes develop in spring, which is most likely, the best approach is another application to kill these weeds. At this stage it's usually better to kill everything, plant a summer annual crop, and kill new annual bromes again in the fall. The second spring, again kill new weeds and repeat the summer annual crop treatment. Finally, after a third fall and spring of killing these winter annual bromes, the number of viable weed seeds remaining in the soil will be low enough that new pasture can be planted.

It takes a long, dedicated process to recover pastures overtaken by winter annual bromes. There are no shortcuts.

Bruce Anderson
Extension Forage Specialist, Lincoln