August always seems to be a time when certain weeds can become quite noticeable in pastures. There can be a variety of common annual weeds like sunflowers, lambsquarters or kochia.
Perennial weeds like western ragweed, ironweed and verbena can be plentiful in some pastures as well. In areas of pastures that have relatively thin grass stands, in areas where animals congregate, or if some overgrazing has occurred, they can be very visible.
Spraying weeds now does little good. Many weeds are too large to kill. On both annual and perennial species that produce seed, herbicides might only reduce some seed production. If the goal is to improve appearance, shredding areas that have an abundance of weeds might be the best option, and may reduce some seed production too, if it’s not already too late.
Two other approaches are better for long-term weed control. First, focus on the grazing management of your pastures. This includes using the proper stocking rate and developing a good rotational grazing plan. An important objective is to increase the health, vigor and density of your grass. Healthy, competitive grass stands are essential to reduce weed populations economically over time.
Second, target herbicide applications for when they will do the most good. Both perennial and annual species can be better targeted with a spring application when plants are smaller and able to be controlled. For perennials, if a second application is needed, waiting closer to a killing frost is best. These fall applications can be more effective as more product is translocated down to the roots of the weeds.
Pasture weeds may look unsightly now; but hold off on spraying. Improve grazing management and time herbicides for the best window of control so herbicides won’t be needed as often in the future. On the bright side, for areas that have had good rains this summer, it is likely that annual weeds will be less abundant next year as pasture grasses had a chance to build up vigor and reproduce. — Jerry Volesky, Nebraska Extension
