Though hardy and relatively low-maintenance in nature, bermudagrass lawns can occasionally be afflicted by an invasion of crabgrass. This tenacious weed competes with your lawn for water and nutrients, slowly overwhelming your grass and ruining your lawn's appearance. Prevent this from occurring by maintaining your lawn's health and taking preventative measures to stop crabgrass from sprouting in a bermudagrass lawn in the first place.
Water bermudagrass lawn correctly to encourage a healthy lawn, which is less susceptible to crabgrass invasions. Water the lawn once or twice a week, using enough water to moisten the soil to a depth of 4 to 6 inches. This encourages deep root development.
Feed your lawn to promote dense growth that chokes out all other types of vegetation, including weeds such as crabgrass. Fertilize from the spring through the fall approximately once every four to six weeks. Use a standard lawn fertilizer and apply it according to the label's guidelines, since potency varies by product. Follow the fertilizer with a short watering session to help carry the fertilizer's nutrients into the soil.
Mow your bermudagrass lawn as high as possible. This increases the shade at the soil level and reduces the chance of weed seeds sprouting, according to the University if Minnesota. Common bermudagrass can be mowed to a height of 1.5 inches, while hybrid bermudagrass species can be mowed at 2.5 inches.
Apply a pre-emergent herbicide such as benefin or prodiamine at the start of your bermudagrass lawn's growing season in April. This stops any crabgrass seeds from sprouting but doesn't harm your lawn. This is ideal if mowing your lawn higher hasn't sufficiently reduced crabgrass populations in your lawn in the past.