A fine-textured warm-season turf grass best grown in the southern United States, Bermudagrass (Cynodon spp.) is a low-growing, wiry perennial. During the heat of summer, it grows quickly, especially in fertile, moist, well-drained soils. It spreads via two types of shoots: above-ground stolons and underground rhizomes. Improper growing conditions, mismanagement or a bout with insect pests or diseases may lead to random yellow or dead spots in a Bermudagrass lawn. Dead patches of grass decompose to reveal bare soil.
Ideally, a Bermudagrass lawn will be thick so no bare soil shows through the carpet of light green leaf blades. Lack of sunlight quickly causes Bermudagrass to grow with fewer stems and leaves, creating thin areas where soil is seen. Provide this grass with no less than eight hours of uninterrupted sunshine daily. A wet soil pocket can cause the grass to yellow and die out, and dumping fertilizer in a concentrated area or during the heat of midsummer can scald the lawn, leading to grass death and the formation of a bare spot. If thatch builds up, it can choke out light and water and kill areas of Bermudagrass; aeration or de-thatching in late spring often prevents excessive thatch build-up.
Mowing Bermudagrass inconsistently or at the improper height can create bald spots or scalped areas. Never remove more than 40 percent of the height of a Bermudagrass lawn at any mowing event. Bermudagrass lawns may be maintained quite short, between 1/2 to 2 inches, but more frequent mowing is needed so that not too much leaf height is removed at a time. During the fall and winter months, when temperatures drop below 50 degrees, Bermudagrass turns dormant, taking on a tan color. When it's dormant, mowing is not needed, but continued walking and wear atop the lawn creates thinning areas that must be grown back the following spring and summer.
Armyworms, cutworms, sod webworms, white grubs, Bermudagrass mites and mealybugs can afflict Bermudagrass lawns, especially if the plants are stressed or weakened from poor management or bad growing conditions. The mites and mealybugs are potentially the most serious threats. These insects feed on the juices in leaves, stems or roots, causing plants to yellow and die back. Nematodes, which aren't insects, but a pesky soil microorganism, are most likely to appear in warm, dry soils -- especially in sands -- and cause random patches of dead grass if present.
Fungal diseases are the biggest concern with Bermudagrass. Slow-draining soil, over-irrigation and allowing the lawn to grow too tall between mowings creates an environment for fungi to proliferate from spring to fall. Dollar spot, spring dead spot, leaf spot, brownpatch and Pythium rot may occur in the lawn, creating spots and streaks of yellow to brown areas. If a fungicide isn't applied and growing conditions don't improve, the lawn spots die out, leaving scattered bare spots.