Weed populations have exploded recently in many pastures. Plants like ragweed, ironweed, goldenrod, and vervain have become a common sight. Many pastures were drought stressed last year and recent summer rains have stimulated a late season revival of these weeds.
What do you do about weeds at this time of year? Applying herbicides for weed control does very little good on mostly mature weeds this time of year. Spraying may reduce some seed production if applied early enough and should make pastures look nicer, but overall, herbicide applications at this time are not an economically sound investment. Mowing would probably be a more attractive alternative to limit seed production in these species.
Long-term weed control in your pastures is certainly a better financial investment. Good grazing management next year that leaves some residual grass cover can go a long ways towards minimizing the competitiveness of many of these weed species. Improving the health, vigor, and density of your grass stand makes it more difficult for these weeds to get started in your pastures.
Timing herbicides applications for when weeds are most susceptible is critical to making the most economical use of these products. Spraying in early-June is generally when chemicals will be most effective, especially with herbicides like 2,4-D, Grazon, Banvel, or Curtail.
But don’t put the sprayer away for the winter just yet. Fall is one of the best times of the year to use herbicides to control both musk and Canada thistle. If you weren’t able to get out and control them this spring, you still have another chance.
With recent rains, Musk thistle seedlings have probably sprouted into a small, in a flat rosette and the rhizomatous Canada thistle has sent up new tillers. This new growth is very susceptible to herbicides at this time of year.
Using 2,4-D or Ally are probably your best bet for the money. However, as it gets colder, a little Banvel mixed with 2,4-D will result in a better kill on musk thistle or use curtail before the soil freezes.
If it gets late and you are not sure how effective herbicides will be, use Tordon 22K instead because Tordon has a lengthy soil residual that will continue to work next spring.
Read more Range Science 101 articles from Eric Mousel