Weeds that have invaded pastures due to this summer’s wet weather should be controlled before the problem worsens, says Kevin Bradley, University of Missouri weed scientist.

“Cocklebur and ragweed are thick this summer and have been emerging in a lot of pastures in recent weeks,” he says. “If these weeds aren’t controlled, they can take over pastures by fall. All you’ll have is a big weedy mess.”

There are good controls available if applied while the weeds are still in the vegetative state, says Bradley. “Grazon P+D, GrazonNext, ForeFront, and 2,4-D plus dicamba are just a few of the herbicides available for the control of these annual weeds.”

Broadleaf weeds reduce pasture growth for grazing livestock. The herbicide will control the annual broadleaf plants in the pasture, which include most of the troublesome pasture weeds. Herbicides also kill legumes in the grazing mix, but those can be re-established with frost seeding next spring.

Mowing before weeds set seed heads also can provide some degree of weed control. However, a second mowing might be needed, as weeds will do their best to produce seed before the end of the growing season, Bradley cautions.

Weeds form a canopy that shades pasture grass leaves, cutting growth for livestock grazing. In management-intensive grazing systems, ragweed in young stages provides nutritious forage. However, it soon becomes inedible.

Rob Kallenbach, Missouri Extension forage agronomist, recommends mowing pastures that are out of control to remove seed heads on cool-season grasses. Clipping fescue pastures in particular encourages fall regrowth for stockpile grazing this winter.