Take Grassburs Out of the Picture Early

Sunday Express News
Gardening, Etc.
February 8, 2004

By Nathan Riggs

For those who live in areas with sandy soil, there are plenty of benefits when it comes to landscaping. Most wildflowers love sandy, well-drained soils. Azaleas, pines, and hydrangeas thrive in the lower pH levels and quick drainage that these soils provide. A few weeks ago, our Extension article talked about dealing with gophers in sandy soil. This week, let’s talk about dealing with those banes of bare feet: grassburs.

Grassburs, also called Southern Sandbur, prefer sandy soils, but will grow in other types of soil if conditions are proper for them. Grassburs are easily recognized by their flattened growth habit where the plant radiates outward from a central point in all directions. The bases of the stems sometimes develop a purplish color as well. Once the seed heads (stickers) form, the stems grow upward. It is important to recognize grassburs early so they can be physically removed or isolated before they produce seeds and get more difficult to remedy.

Controlling grassburs can be accomplished in many ways, but none of them are rapid. If the infestation is light, they can be hand pulled and discarded or spot sprayed with glyphosate (Round-Up and others) herbicides. Unfortunately, most people who have grassburs have become very good at growing them and have dense stands to control.

There are two basic methods for controlling established grassbur areas: pre-emergent and post emergent. Pre-emergent control involves applying treatments before the grassbur seeds germinate. In South Texas, the target date for the first pre-emergent grassbur control application is March 1 or before soil temperatures reach 52 degrees F. The best products on the market for pre-emergent treatment of grassburs in non-grazed areas are Amazeâ, Surflan, PreM, and Weed Stopper. Apply these products twice at 6-week intervals for light infestations or every 6 weeks through September for heavy infestations. After applying the granules, be sure to apply 10 minutes of light irrigation to incorporate the chemical into the soil.

Treating grassburs once they are green and growing adds a few more tools to the arsenal. In lawns with Bermuda grass and grassburs, a couple of good products to apply are MSMA or Imageâ. For best results, apply these when average daytime temperatures reach 75 degrees F. For St. Augustine or Centipede lawns, do not use MSMA because it will injure and most likely kill those grasses. Use Imageâinstead.

In pastures that are grazed or harvested for hay, best bets are Plateauâ and Oasisâ herbicides. Neither of these products is cheap, but their higher cost may offset by increased grass production, grazing benefits or improved hay quality. For those who are wondering, atrazine is no longer approved for treating grassburs in grazed or hay pastures.

With all of this in mind, there is still one important thing to remember. A healthy patch of grass will out compete and choke out grassburs in most cases. Proper fertilization, irrigation, and aeration will allow your grass to win its battles with grassburs every time.
Don’t let grassburs get out of hand in your lawn this year. It’s not too late to consider one of the pre-emergent herbicide options for your turf and it’s the perfect time to plan for treating them when temperatures warm up. Be careful when using MSMA products near St. Augustine or Centipede grasses and keep your lawn healthy so it can fight those grassburs on its own.

For more information and referenced facts for this article check out Texas A&M Turf specialist Jim McAfee’s article on the web at http://aggie-horticulture.tamu.edu/plantanswers/turf/grassbur.html.

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Texas Cooperative Extension is implied.

This article was written by Nathan Riggs, Extension Agent-IPM with Texas Cooperative Extension in Bexar County.



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