September 12, 2008

Winter annual bromes often invade thin or overgrazed pastures in fall and early spring. Livestock dislike grazing them so over time they can take over and make large patches of pasture nearly worthless.In warm-season grass pastures and rangeland, Plateau and glyphosate herbicides can kill these annual bromes without harming the desirable grasses if used correctly. 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 still remains, spraying Gramoxone in November can help. This will kill annual bromes that have emerged, but also will injure desirable grasses. Unfortunately, annual bromes that emerge next spring will not be affected.

If this amount is small, grazing and fertilizer management that strengthens desirable grasses may revive pasture productivity.However, if many annual bromes develop in spring, the best approach is to again kill these weedy grasses. 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 next, or 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
Forage Specialist