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Weed-Control Calendar for Sports Turf

Weed identification is a critical factor in chemical weed control. If you do not identify the weed correctly, it may be difficult to select an effective herbicide. Resources for weed identification are listed at the end of this publication.

February-April

Mowing

Mowing is an easy and effective way to remove unsightly weed growth. The first time you mow the field each spring, set the mower at the lowest possible setting but not low enough to scalp the turf. The primary purpose of low mowing is to remove dead turfgrass leaves and stems and winter weeds so the emerging turfgrass is not shaded. Close mowing also permits more sunlight to reach the soil surface and helps warm the soil. While this creates a favorable environment for turf growth, it also creates an environment suitable for weed emergence. Do the first close mowing before any signs of spring green-up.

After the initial low mowing, mow as needed to the recommended mowing height, remembering to mow frequently enough that not more than one-third of the plant material is removed each time.

Fertilizer

Proper fertilization helps make the turfgrass competitive with weeds. To determine the fertility of the field, take a soil sample and have it analyzed by a reputable laboratory. Contact your Extension agricultural agent to assist with soil sampling. Apply fertilizer as soon as there is no danger of frost. Refer to Extension Publication 2086, Management of Sports Fields in Mississippi, for specific information. Generally, 1 pound of actual nitrogen per 1,000 square feet is recommended to provide adequate nitrogen for the turfgrass to start growing. If the soil test report indicates less than medium levels of potassium, use a fertilizer that also contains enough potassium for good root growth and development.

Preemergence Herbicides

If the turf is badly worn or damaged from play, do not use preemergence herbicides, since many preemergence herbicides inhibit root development of recovering turfgrass. In those areas where there is a good cover of healthy turfgrass, you can use a preemergence herbicide to control summer annual weeds.

To prevent weed seedling emergence, apply preemergence herbicides and water them into the soil before weed seed germination starts. Apply a preemergence herbicide by February 1 to February 15 in southern Mississippi, February 15 to March 1 in central Mississippi, and March 1 to March 15 in northern Mississippi.

Numerous preemergence herbicides and weed and feed products that contain both fertilizer and a preemergence herbicide can be used on warm-season turfgrasses. Refer to the glossary of Extension Publication 1532, Weed Control Guidelines for Mississippi, for a list of those products. Remember to read the product label for directions to use the product safely. If you use a weed and feed product or granular herbicide formulation, apply one-half the recommended rate in one direction and apply the other half perpendicular to the initial application to minimize the chance of streaking. Generally, a preferred preemergence product contains one of the dinitroaniline herbicides (benefin, oryzalin, pendimethalin, or prodiamine), dithiopyr, or metolachlor. Do not apply atrazine after April 15.

There are two approaches that you can take for spring preemergence herbicide applications. Crabgrass seeds start to germinate when soil temperatures are around 55 °F, but goose grass seeds don't germinate until soil temperatures reach around 65 °F. Therefore, many professional turfgrass managers prefer to split the spring preemergence herbicide application and apply one-half the recommended rate in March and the other half in early May. This strategy provides the highest level of control for these troublesome grassy weeds.

Postemergence Herbicides

Postemergence herbicides control emerged weeds. Many winter broadleaf weeds that escaped earlier treatments and mowings, as well as some summer broadleaf weeds, need treating. A mixture of two or more of the following ingredients is preferred for postemergence applications: 2,4-D, MCPP, MCPA, mecoprop, or dicamba. Many trade names that contain various concentrations of these ingredients are available at lawn and garden centers, agrichemical dealers, hardware stores, and other sites. Use caution when purchasing, and purchase the most concentrated formulation available.

May-July

Mowing

Mow as needed to the recommended mowing height, remembering to mow frequently enough that not more than one-third of the turf vegetation is removed each time.

Fertilizer

Apply 1 pound actual nitrogen per 1,000 square feet.

Preemergence Herbicides

If you split the spring preemergence herbicide, apply the second half of the recommended rate 2 months after the initial application. Do not apply simazine after June 1.

Postemergence Herbicides

Apply the three-way mixtures to control emerged broadleaf weeds as needed. Remember that small weeds are more easily controlled than larger weeds. Large weeds may require two applications 10 days to 2 weeks apart for complete control. If nutsedge has been identified as a problem weed, use Manage or Image for control.

If annual grasses, such as crabgrass, or perennial grasses, such as dallisgrass, have emerged, apply a postemergence grass herbicide. In Bermudagrass, MSMA is the preferred treatment for most annual or perennial grasses. Two applications will be required for larger annual grasses, while three may be necessary to control perennial grasses. Apply 14 to 21 days apart. You may use other treatments instead of MSMA, although these may be more expensive. For example, you can use Dimension (dithiopyr) to control very small crabgrass before tillering.

August-October

Mowing

Continue to mow as needed to the recommended mowing height, remembering to mow frequently enough that not more than one-third of the plant material is removed each time.

Fertilizer

Apply 1 pound actual nitrogen per 1,000 square feet in August and September, but reduce the amount to 0.5 lb nitrogen per 1,000 square feet in October. Apply potassium according to guidelines given in Extension Publication 2086, Management of Sports Fields in Mississippi.

Overseeding

Overseed when soil temperatures reach 68 to 72 °F at a 4-inch soil depth. This generally occurs between September 15 and October 1 in northern Mississippi, October 1 and October 15 in central Mississippi, and October 15 and November 1 in southern Mississippi. Most fall preemergence herbicide treatments will kill or severely damage the ryegrass used for overseeding, just like the winter weeds. Therefore, do not apply a fall preemergence treatment in areas targeted for overseeding.

Preemergence Herbicides

Apply fall preemergence treatments before winter weeds begin to emerge. Do not apply simazine before September 1; do not apply atrazine before October 1. Herbicides such as oryzalin, benefin, pendimethalin, and prodiamine, which give no control of emerged weeds, must be applied by October 1 in northern Mississippi, October 15 in central Mississippi, and November 1 in southern Mississippi.

Postemergence Herbicides

Continue to treat perennial grasses with MSMA. Re-treat nutsedge populations if necessary. Use a herbicide mixture to control remaining broadleaf weeds. Watch carefully for wild garlic emergence. The three-way mixtures provide excellent control of wild garlic if applied while plants are small and actively growing. Multiple applications over several years will be required to reduce wild garlic populations.

November-January

Mowing

Continue to mow as needed to the recommended mowing height, remembering to mow frequently enough that not more than one-third of the plant material is removed each time.

Preemergence Herbicides

Weed and feed combinations are not recommended for fall applications on warm-season turfgrasses unless the product contains the appropriate levels of nitrogen (N), phosphorous (P), and potassium (K) needed, according to soil test reports. Weed and feed combinations that contain atrazine will control small emerged weeds as well as providing preemergence control.

Postemergence Herbicides

Use a herbicide mixture to control small, emerged winter broadleaf weeds. The three-way mixtures provide excellent control of emerged wild garlic if applied while the plants are small and actively growing. Image also controls wild garlic but can inhibit Bermudagrass growth, so use caution with this herbicide. Do not apply Image to Bermudagrass until after the first killing frost, and apply no later than January 1 to prevent Bermudagrass injury. Roundup can be wiped onto individual clumps of wild garlic if populations are sparse enough for individual treatment.

Additional Resources

Weeds of Southern Turfgrasses can be ordered from the following sources: Bulletin Room, Alabama Cooperative Extension Service, Duncan Hall, Auburn, AL 36849; or University of Florida Publications, P. O. Box 110011, Gainesville, FL 32611-0011; or AG Business Office, Box 109 Conner Hall, The University of Georgia, Athens, GA 30602.

You can order Publication 1532, Weed Control Guidelines for Mississippi, from your county Extension office or from John Byrd, Department of Plant and Soil Sciences, Box 9555, Mississippi State, MS 39762. Cost is $5 per copy. Enclose check made payable to Mississippi State University Extension Service with order.

By John D. Byrd, Jr., Ph. D., Extension Weed Specialist, G. Euel Coats, Ph. D., Professor of Weed Science, and Steve Kelly, Research Associate II.

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.

Publication 2197
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

Copyright by Mississippi State University. All rights reserved.

This document may be copied and distributed for nonprofit educational purposes provided that credit is given to the Mississippi State University Extension Service.

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