Weeds seem to be a constant problem in most pastures and hayfields across Tennessee and the Southeast. Often producers do not notice how infested a pasture or hayfield is until spring, when the weeds bloom and become hard to miss. The weed species may change from year to year, but rarely do weed infestations disappear on their own. Usually some type of herbicide is needed to break the cycle of weed infestation in these fields. The problem is that if the herbicide isn’t applied until the weeds bloom, its effectiveness is decreased and weed seed is already produced.
In order to most efficiently use herbicides to kill weeds, it is important to know what weed species are present. That will help determine the herbicide and rate needed for effective control. The time way to do that is to walk pastures this time of year, looking down to see the type and amount of weeds present.
Winter weeds germinate in September, October and early November. They grow during the winter, and then produce blooms in April and May. When temperatures get hot, these plants usually either die or go dormant, and will remain so until the next fall. Buttercup, musk thistle, curly dock, and the plantains are examples of winter weeds. In order to be the most effective controlling the weeds, they need to be sprayed sometime between December and March. You are trying to spray after most germination has occurred, but before the plants start to bloom.
Best conditions to kill winter weeds
December to March is a long window for adequate weed control. Look for three days in which the high temperature reaches approximately 60 F. After three days, the weeds will be growing adequately to take in the herbicide applied, and successful weed control will be achieved. If you get these three days in December, go ahead and apply the herbicide. If you miss the window, you will still have more time as the winter progresses.
Herbicide recommendations for specific weeds
Buttercup, musk thistle - These weeds are relatively easy to kill. Two pints per acre of 2,4-D will provide excellent control. Staying below two pints per acre has the added benefit of not killing established white clover. If the 2,4-D is applied before early January, you can come back in during the last two weeks of February and seed clovers if needed.
Buckhorn and broadleaf plantain- these weeds are slightly more difficult to control. A higher rate of 2,4-D will be needed (4 pints per acre), or stronger herbicides will be needed. Three pints per acre of a 2,4-D and dicamba mix (Weedmaster, Rangestar) will work, or use 1.6 pints per acre of GrazonNext HL. If the plantains are found in orchardgrass, you can also use 2 oz per acre of Chaparral.
Curly Dock – if curly dock is an additional weed found in the field, 1.6 pints per acre of GrazonNext HL will do an adequate job in a tall fescue field. If the field is orchardgrass, 2 ounces per acre of Chaparral is another option.
If you have some other weed that is a problem in your field, contact your local Extension agent for a specific weed control recommendation.