Over the last few years, we pasture and range consultants have received a number of inquiries from producers wanting to know how to get rid of "wiregrass" in their pastures. Their question leads directly to several questions of our own to help us refine our answer for their particular situation. The discussion goes something like this ...
Producer: I have wiregrass in my pastures. How do I get rid of it?
Consultant: There are several grasses that are often called "wiregrass." Most often wiregrass is Oldfield three-awn - an annual warm-season grass that is usually found on areas that have been disturbed or on low fertility soils. It is also commonly called "ticklegrass." Other grasses such as prairie dropseed and Texas wintergrass are sometimes referred to as "wiregrass." Both of these are perennial grasses with the dropseed being a warm-season grass and the wintergrass being a cool-season. What does the "wiregrass" look like?
Producer: It is short and wispy with thin leaves and grows in the spring and summer when there is moisture. Cattle will not eat it. The seedheads are like fine hair, but with sharp points. If they get into your socks, they are the devil to get out.
Consultant: Describe your recent management of this pasture. (We usually get one of the three answers below.)
Producer (answer 1): It is a native pasture that has been hayed for as long as I can remember. It has never been fertilized. I usually bale it twice a year if weather permits. It is very difficult to cut the areas where it is thickest. It wraps around the cutter bar and makes a mess. Then there is nothing to bale once it dries.
Producer (answer 2): It is a bermudagrass pasture we sprigged a couple years ago. We got a fair stand that first year, but the weather has been dry and fertilizer was too high to fertilize like we should have. The second year, we did not see much bermudagrass and what was there was not very productive. The wiregrass starts growing before the bermudagrass and covers up what bermudagrass there is.
Producer (answer 3): It is an old crop field that has gone back to grass. We have not done anything to it for as long as I can remember, but graze cattle on it.
Consultant: That sounds like conditions Oldfield three-awn thrives in. You can send in a sample of the plants for us to identify or look up "Oldfield three-awn" in the Plant Image Gallery on the Noble Foundation Web site and see if the pictures look like what you observed.
Producer: Assuming it is the three-awn, how do you get rid of it? What herbicide will kill it?
Consultant: You probably won't like the answer. Let's address the latter question first. There is no herbicide labeled for the control of Oldfield three-awn. If you are sprigging bermudagrass, Diuron is a pre-emergent herbicide labeled for the control of annual forbs and grass species. But in existing pastures, there is no good remedy. About the only chemical that can be legally used is glyphosate, and it is nonspecific - it will kill most species of grass or forbs it contacts. Unless you can spot spray or treat Oldfield three-awn before the other grasses emerge in the spring, we wouldn't recommend it.
Now to address your first question, the presence of Oldfield three-awn indicates low soil phosphorus or low pH. In bermudagrass pastures, we recommend that you fertilize according to soil test recommendations to encourage the bermudagrass stand to thicken and cover. Relative to native grass, we don't usually recommend haying or fertilizing native grass pastures because there is rarely enough production to justify the cost. What we do recommend is that you graze the native grass pastures and no longer use them for hay production. Good grazing management, with proper use and recovery periods, will usually allow for range improvement over a few years. If haying is the only alternative for a native pasture, hay it only once a year by July 1.
Producer: You're right - it is not what I wanted to hear, but now I know. I may have to change or improve the management on this piece of land. Thanks!