With late summer rains and favorable conditions, weeds exploded in many pastures. Plants like ragweed, ironweed, goldenrod, and vervain are abundant everywhere, says Bruce Anderson, University of Nebraska forage specialist.
Because many pastures only had short grass as competition, these weeds grew almost unchecked when a series of late-season rains stimulated growth. Only pastures or areas in pastures with thick, relatively tall grass stands have few weeds.
Spraying weeds now does little good. Many weeds are too large to kill so herbicides might only reduce some seed production and make pastures a bit more attractive. Shredding would actually work better to reduce weed seeds if it's not already too late.
Two other approaches are more important for long-term weed control. First, do more rotational grazing next year to improve the health, vigor and density of your grass. Leave more residue when rotating to maintain higher competition. Healthy, competitive grass stands are essential to reduce weed populations economically.
Second, target herbicide applications for when they will do the most good. Early- to mid-June usually is most effective, especially with herbicides such Grazon, Curtail, 2,4-D, and Banvel, according to Anderson. Most perennial weeds and many annuals are sensitive to chemicals in June. Weed control, along with good grazing, will thicken your grass stands so herbicides won't be needed as often in the future.