Bermudagrass (Cynodon dactylon), a warm-season grass, commonly invades during the summer when cool-season grasses such as Kentucky bluegrass and fescue are under heat and drought stress. It is a problem only in full sun, i.e. it does not grow well in shade. You can spot treat heavily infested areas of Bermuda with a nonselective herbicide (glysophate) or a grass herbicide (fluazifop) , but these treatments will kill fescue as well. Mow the fescue high, which will select against bermuda and help reduce the competition.
