ANR-104, Revised Oct 1996. John W. Everest, Extension Weed Scientist, Professor, and Don Ball, Extension Agronomist, Professor, both in Agronomy at Auburn University

---

Controlling Smutgrass in Alabama Pastures

Smutgrass (Sporobolus poiretti) is a warm-season, perennial, bunch-type grass which is a native of tropical Asia. This grass was named for the black fungus which usually attacks the seedheads, giving them a blackish, smutty appearance. The plant is a prolific seed producer and, since the seed are very small, they are easily spread by wind, water, and animals. The grass has spread through most of South and Central Alabama in recent years after being originally introduced from Florida.

Unfortunately, smutgrass is an undesirable pasture species. It is extremely unpalatable, and cattle will eat it only under adverse circumstances. Because it does not receive grazing pressure, smutgrass often flourishes in Alabama pastures and crowds out desirable species.

Until several years ago, landowners relied on the herbicides Dowpon M or Dalapon 85 to control this pest. This herbicide treatment caused considerable injury to bahiagrass and bermudagrass and resulted in reduced grazing for several months. These products are no longer sold and are unavailable for use.

The herbicide Velpar was granted a state label in early 1990 for the control of smutgrass in established bermudagrass and bahiagrass pastures. Velpar is available as a 90-percent soluble powder or as a 2-pound-per-gallon liquid formulation. Both formulations are labeled for smutgrass control.

The use rate is 3/4 to 1/4 pounds per acre for Velpar 90SP or 2-3/4 to 4-1/2 pints per acre for Velpar 2L. The low rate should be used on coarse-textured sandy soils, and the high rate should be used on fine-textured clay soils. In fields which have soils of variable texture, the lowest appropriate rate should be used to avoid excessive injury to forage grasses. This treatment should not be applied to newly established pastures because severe injury is possible. Do not apply this herbicide in the root zone of any desirable woody plants and trees.

Make only one application per year, using a boom-type sprayer. The application should be made in a minimum spray volume of 25 gallons per acre. Sprayer calibration is very important and uniform spray application is critical to prevent excessive injury to desirable forage crops. Cool-season annual grasses and legumes overseeded in the bahiagrass or bermudagrass will be killed by this treatment.

The best smutgrass control is achieved when small plants (2 inches tall or less) are treated in the spring and when 1/2 to 1 inch of rainfall occurs within 2 weeks of application. Insufficient rainfall may allow the treated smutgrass plants to recover from the injury, while heavy rainfall may result in poor control or injury to desirable forage species. Apply the herbicide when the air temperature is above 80 degrees, when humidity is high, and when the soil is moist. Velpar should not be applied when the soil is dry.

The crop injury associated with the use of Velpar is often temporary. It can be seen as a yellowing or leaf burn on treated bermudagrass or bahiagrass. Under good growing conditions, the desirable forage grass should recover in 2 to 3 weeks. Cattle producers should not graze or feed treated forage or hay to livestock within 37 days of application.

Landowners with a smutgrass problem must plan ahead for their spring control programs. Since small smutgrass must be actively growing at the time of application, a timely application can be made in May (in most years). In addition to applying herbicides, landowners should fertilize and lime their pastures according to soil test recommendations to improve the overall growth and vigor of their forage grasses.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.