By Keith Allen University of Tennessee Agricultural Extension agent

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 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 they 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 at 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.

The best conditions to kill winter weeds occur from December to March. It is a long window for adequate weed control.

Look for three days in which the high temperature reaches approximately 60 degrees Fahrenheit. 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.

More information concerning weed control, seeding, sprayer calibration, as well as many beef topics, can be found on the University of Tennessee Institute of Agriculture website, www.utbeef.com.