How to Control Crabgrass Problems

The real crabgrass invasion came in the late 19th century when European immigrants brought crabgrass with them to be used as a grain. Crabgrass was soon abandoned, however, in favor of the more easily harvested and processed corn and wheat grown in United States. The abandoned crabgrass soon became a serious pest, and finally a major lawn weed. It is also a problem as an impurity in grass seeds. The plant is extremely productive, a single plant often producing over 8000 seeds.

Crabgrass is an annual plant. Seeds germinate from mid March to mid April, depending on location and weather conditions. As soil is disturbed, or when wet weather persists, germination may occur into the summer. In fall, following seed production, the plant dies, dropping large quantities of seeds and becoming a patch of brown dead grass where it crowded out the more desirable bluegrass.

In the lawn, crabgrass is most easily and effectively killed when the young seeds germinate in spring. Herbicides effective at this time of development are called pre-emergence herbicides. They cannot kill a plant after the small seedling has grown into the light and developed green leaves. One of the most popular crabgrass killers during recent years has been DCHA (Dacthal). Since its introduction about 40 years ago, it has maintained a good reputation for home lawn use.

Bensulide (Betasan) gives consistent crabgrass control. It has a longer residual life than many of the other materials, and therefore might interfere with fall seeding if fall lawn repairs become necessary. The longer residual life, however, helps reduce chances for later summer crabgrass germination.

Benelin (Balan) also gives good control. Careful application of this material is necessary. Applications slightly less than recommended can give poor control, and slightly higher than recommended can cause injury. None of the three materials listed previously can be used on new lawns. Siduron (Tupersan) may be applied at the time of seeding, as well as on an established lawn.

Although these and other pre-emergence herbicides may be purchased separately, they are often part of combination herbicide and fertilizer products (weed-and feed available for spring lawn care. In these products they are added as a granular formulation but pre-emergence herbicides may also be purchased separately for spray application.

In many years a single application of some of these materials provides good crabgrass control for the season. In wet years, or in low-lying moist areas, a second herbicide application in early June may be necessary to insure a crabgrass-free lawn. When applying pre-emergence herbicides, best control is obtained from a uniform application, avoiding skips and overlaps. Skips mean crabgrass, overlaps may mean damage to existing grass. As with any other pesticide, read and follow label directions carefully.

http://en.wikipedia.org/wiki/Crabgrass