Crabgrass and Bermuda grass are similar in appearance. Both are warm-season grasses that grow well in hot weather, but crabgrass is largely unwanted in lawns by homeowners. Crabgrass has a faint hint of blue to it and is an annual grass that appears in hot summer months. Killing crabgrass in a Bermuda grass lawn is a little tricky, because you don't want to cause any damage to the grass you want to keep.
Obtain chemical crabgrass killer found in lawn and home stores. Some varieties of herbicides will destroy crabgrass without harming Bermuda grass. Products which contain the active ingredient sethoxydim are effective in killing crabgrass, but will not hurt Bermuda grass.
Avoid mowing the lawn for five to six days before using chemical herbicides on crabgrass. Longer leaf blades will soak up more of the chemical and this will work to kill crabgrass more quickly.
Wait for a clear day with no rain, with temperatures lower than 85 degrees Fahrenheit. Hot weather will put more strain on the grass. If possible, choose a day when weather forecasters are calling for two to three clear, rain-free days in a row.
Spray herbicide on the affected areas of the lawn during the late afternoon or early evening, never in the hottest part of the day.
Avoid watering the lawn for at least 24 hours after spraying herbicides on crabgrass.