Crabgrass (Digitaria spp.) and bermudagrass (Cynodon dactylon) are two types of grass commonly seen in North American yards. The former is typically a weed and the latter is usually a desirable grass species, but both can be a nuisance and may need to be killed. Pull on protective gear like gloves, a face mask and eye goggles and treat your yard with a variety of chemical and physical controls. Your strategy depends on if you need to remove only crabgrass, only bermudagrass, or both together. Apply all herbicides according to their labeled guidelines, since toxicity varies by product.
Kill bermudagrass without killing other types of vegetation, such as shrubs and flowers, by using a sethoxydim-, clethodim- or fluazifop-based herbicide, which is grass-selective and doesn't harm other plants. Wearing protective clothing, apply the herbicide in the spring when the bermudagrass is 4 to 6 inches tall. If some bermudagrass survives, reapply the herbicide when the regrowth is 4 to 6 inches long.
Eradicate crabgrass in desirable grass, such as zoysiagrass or fescue. Spray the desirable grass in January or February with a pre-emergent herbicide like benefin, pendimethalin or bensulide; this keeps crabgrass seeds from germinating. Follow with dithiopyr, a post-emergent herbicide, to kill any crabgrass that already germinated.
Destroy both crabgrass and bermudagrass together, an ideal approach when you're renovating a yard and want to remove all grassy vegetation. Spray the entire area with a glyphosate-based herbicide. Glyphosate is a systemic herbicide that kills both the top growth and the grasses' root system.
Kill the grasses together organically if you don't wish to use a toxic chemical like glyphosate. Cover the grassy area with plastic tarp and weigh down the edges with bricks, rocks or other heavy objects. The heat from the sun will bake the grass under the plastic and kill it over the course of three to four weeks.