Several preemergence herbicides will control crabgrass in established lawns. These include benefin, bensulide, dithiopyr, and pendimethalin. Often these herbicides are combined with a turf-type fertilizer. This allows the gardener to apply a preemergence herbicide and fertilizer with one application. This herbicide effectively controls crabgrass without affecting the germination of the turfgrass seeds.
Gardeners also can control crabgrass by applying corn gluten meal.
A corn milling byproduct, corn gluten meal inhibits the root growth of crabgrass seedlings. Unable to develop roots, the crabgrass seedlings die. In addition to crabgrass, corn gluten meal offers preemergent control of dandelion, plantain, lambsquarter and other weeds. While corn gluten meal is not as widely sold as other preemergence products, it is available at select garden centers and mail-order companies. The keys to successful control of crabgrass in lawns are correct timing of the preemergence herbicide application and proper application of the material.