Control Weeds Before Plants Set Seeds

July 26, 2010 04:34 PM

Wet weather has spurred weed growth in pastures this summer, 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 said. “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 weed controls available if applied before the plants set seed, while still in the vegetative state, Bradley said. “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 gazing livestock. The herbicide will control the annual broadleaf plants in the pasture, which include most of the troublesome pasture weeds. Unfortunately, herbicides also kill legumes in the grazing mix. However, those can be re-established with frost seeding next spring.

Mowing these pastures before weeds set seedheads 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 cautioned.


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.


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


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