Bermuda grass is a highly resilient warm-season turf, prized for its ability to thrive under high heat and heavy use across warm climates. Despite its tough nature, the grass is susceptible to environmental, biological, and maintenance-related stressors that can cause it to thin, turn brown, and appear to be dying. Diagnosing the cause requires a careful review of the symptoms present in the lawn.
Environmental and Soil Conditions
Water stress is one of the most common factors leading to Bermuda grass decline. Severe drought forces the grass into dormancy, resulting in brown, brittle blades that often retain the impression of footprints for an extended time. Conversely, overwatering or poor drainage can cause the turf to become soggy and yellow, as waterlogged soil suffocates the roots and encourages root rot.
The chemistry of the soil also plays a significant role. Bermuda grass prefers a slightly acidic soil pH, ideally between 6.0 and 7.0; deviation from this range can lead to nutrient deficiencies, causing yellowing and weakened growth. Soil compaction, often caused by heavy foot traffic or machinery, restricts the flow of air and water to the roots, leading to shallow root systems and poor nutrient uptake. Damage can also result from chemical stress, such as fertilizer burn, which appears as a rapid, uniform browning shortly after applying too much nitrogen.
Damage from Pests and Insects
Insects that feed on Bermuda grass roots and blades create distinct damage patterns. White grubs, the larvae of various beetles, feed on the root system, which prevents the grass from absorbing water and nutrients. This root damage often makes the turf feel spongy underfoot, and the grass can be peeled back like a loose carpet because the roots have been severed.
Pests that target the grass blades, such as armyworms and sod webworms, cause damage above the soil line. Armyworms, identifiable by an inverted “Y” shape on their head, are known for rapidly chewing the grass blades, leaving behind ragged edges and thin, bare patches. A simple diagnostic test for these surface-feeding pests is the soap flush, where soapy water is poured onto a small area of the lawn to force the caterpillars to the surface. Mole crickets damage the lawn by tunneling through the soil just beneath the surface, creating raised mounds and causing the grass to dry out in the areas above the tunnels.
Identifying Fungal Diseases
Fungal diseases are a common cause of turf death, often triggered by conditions like prolonged leaf wetness or high humidity. Spring Dead Spot (SDS) is a persistent disease that appears as circular, sunken patches of bleached, straw-colored grass ranging from a few inches to several feet in diameter. These spots become visible in the spring as the rest of the lawn emerges from winter dormancy. The fungus responsible for SDS attacks the roots and rhizomes in the fall, making the grass more susceptible to winter injury.
Brown Patch manifests as large, irregularly shaped patches of thinned, brown grass, often developing a characteristic “smoke ring” border during periods of high humidity. This disease is most active in warm, wet conditions and is exacerbated by over-fertilization with nitrogen. Dollar Spot is another common fungal issue, presenting as small, bleached spots, typically the size of a silver dollar, which can merge to form larger irregular areas. The infected grass blades often have hourglass-shaped, tan lesions with a reddish-brown border, and a cobweb-like fungal growth called mycelium may be visible early in the morning.
Cultural Practices and Maintenance Errors
Errors in routine maintenance can weaken Bermuda grass, making it susceptible to pests and disease. Mowing too low, a practice known as scalping, cuts into the brown stems below the green leaf canopy, which stresses the plant and exposes the soil to excessive heat and light. Using dull mower blades exacerbates this problem by tearing the grass tips instead of cleanly slicing them, leaving frayed, white ends that are entry points for pathogens.
Excessive thatch buildup is another contributor to decline. This dense layer of dead and living organic matter sits between the soil surface and the green grass blades. When thatch becomes too thick, it prevents water, air, and nutrients from reaching the root zone, creating an ideal environment for fungal growth and insect habitation. The timing and amount of fertilizer application also impact turf health. Applying too much nitrogen, especially late in the season, encourages lush, weak growth that is highly vulnerable to disease. The overall health of the grass is maintained by following a balanced fertilization schedule.