Winter presents an excellent opportunity to get control of pasture weeds while they’re still small. University of Missouri Extension agronomic specialist Tim Schnakenberg said among the primary winter weeds in pastures are thistles, poison hemlock and spotted knapweed; they germinated in the fall and at this time of year they’re in the “rosette” stage, a circular arrangement of leaves all at a similar height that usually sits near the soil. “Many times, people don’t worry about them – ‘Out of sight, out of mind,’” Schnakenberg told Ozarks Farm & Neighbor. “And that’s true for a while; they don’t give us much trouble, but then they start bolting in the spring, usually about April or May. They get tall and big; they start producing seed and flying in the wind, and the neighbors start complaining – or you’re complaining about the neighbors.”
By then, it’s too late for control because the weeds have already gone to seed, and herbicides don’t work as well on them. The best time to deal with them is early March. Schankenberg said, “For thistle, you can use 2,4-D type products; you can use dicamba type products, or the newer products like Chaparral, Grazon Next and Grazon P + D. It’s not hard to kill a thistle when it’s young; you can use some pretty common products, but the key is getting out there to deal with it. The other option with thistle is to come in and dig them, and that’s pretty labor intensive. A lot of people accomplish a lot by digging, but you do have to make this call – is it worth digging a few, and missing a bunch? If you’ve got a big problem with a field, I tend to suggest that people go ahead and do a broadcast spray on some of these fields.”
For spraying to be effective, Schnakenberg said the daytime temperature has to be 55-60 degrees for several days both before and after the day of application, with no hard freezes at night, in order to get the weeds active and attempting to grow. Those conditions are not common in the winter, so producers should watch for those days and plan to get into the field if the forecast is positive.
Extension recommends Grazon P + D type products, Tordon 22K, Remedy Ultra or Cimmaron for poison hemlock, and Chaparral, Tordon 22K, Grazon P + D type products, and Milestone for spotted knapweed. Schnakenberg says while spotted knapweed is not everywhere yet, “it is growing pretty abundantly on the sides of some major highways in our part of the world and tending to move into pastures. Once it gets into pastures and hayfields it will spread rapidly.”
The winter weed outlook is different in Arkansas. Dr. John Jennings, University of Arkansas Extension forage agronomist, told OFN among the problem weeds are buttercup, henbit, chickweed and little barley; even ryegrass can be a weed problem in bermudagrass hay fields. Treatment can start in late fall and continue up until early March.
2, 4-D will control the broadleaves in either fescue or bermuda. As for weedy grasses like little barley, Jennings said in a bermudagrass hay field, “you can use glyphosate before the bermuda breaks dormancy. Oftentimes, that will happen in Central Arkansas about mid-March; you’ll see green tips, and if you spray glyphosate at that point you’ll set the greenup back by about two weeks in the spring.”
