Bermuda grass is a popular warm-season turf known for its drought tolerance and dense growth habit. Like all turfgrasses, it is susceptible to various environmental and biological stressors that can lead to discoloration. The appearance of brown spots is one of the most common issues faced by lawn managers. Identifying the exact source of this discoloration is the first step toward restoring the lawn’s uniform green appearance.
Identifying the Cause of the Brown Spots
The diagnostic process begins with a close visual and physical inspection to differentiate between abiotic (non-living) and biotic (living) causes. Abiotic issues, such as drought stress or fertilizer burn, typically result in large, irregular patches of uniformly straw-colored grass. Sharp, distinct edges often point toward a disease or pest, while gradual fading suggests a cultural problem like localized dry spots.
A simple physical test, often called the “tug test,” helps determine if root-feeding insects are present. Grasp the grass firmly at the edge of the brown spot and attempt to pull it upward. If the turf lifts easily, it suggests the root system has been severed by white grubs or other subterranean pests.
Further examination requires looking at the individual blades of grass. Discoloration limited to the leaf tips, called “tipping,” is generally a sign of minor drought stress or dull mower blades. Conversely, the presence of distinct lesions, spots, or rings on the leaf blades themselves is a strong indicator of a fungal pathogen.
The Most Common Fungal and Insect Pests
Fungal diseases present with distinct patterns that help narrow the identification process. Dollar Spot, one of the most frequent summer diseases in Bermuda grass, manifests as small, circular, straw-colored patches, usually two to six inches in diameter. When the turf is wet, the individual blades may show small, tan lesions with dark reddish-brown borders.
In contrast, Brown Patch is characterized by much larger, circular areas ranging from a few feet up to several yards across, usually occurring during periods of high humidity and warm nights. The outer edge of the patch may display a distinct “smoke ring” of darkened, water-soaked grass blades. Spring Dead Spot appears as bleached, sunken circles one to three feet wide that reappear in the same location each spring, indicating persistent damage to the rhizomes and stolons over winter.
Insect pests cause damage through direct feeding. White grubs, the larvae of various scarab beetles, reside in the soil and feed on the grass roots, causing the turf to detach from the soil. Damage from grubs is most noticeable in late summer and early fall when the larvae are largest and their feeding is most aggressive.
Surface-feeding pests, such as fall armyworms, consume the leaf tissue itself, leaving behind ragged or chewed edges. These caterpillars move rapidly and cause sudden, widespread defoliation, particularly in late-season turf. Identifying the specific pest by observing the damage type is crucial before applying any corrective treatments.
Immediate Steps for Treatment and Recovery
Once the cause of the brown spots has been accurately identified, immediate action must be taken to halt the damage and initiate turf recovery. If a fungal disease is confirmed, such as Dollar Spot or Brown Patch, the application of a broad-spectrum systemic fungicide is usually necessary to stop the spread. Systemic products are absorbed by the plant and move internally, providing curative action against the established pathogen.
For confirmed insect infestations, such as grubs or armyworms, an insecticide application is the appropriate next step. Granular or liquid insecticides labeled for turf use should be applied directly to the affected area and watered in immediately to ensure the active ingredient reaches the target zone. The timing of this application is important; for grubs, the most effective window is often late summer when the young larvae are present.
Immediate cultural adjustments are also necessary, especially if the cause was abiotic. If fertilizer burn is suspected, the area should be thoroughly flushed with water to leach the excess salts below the root zone. For drought-stressed areas, a deep, slow watering cycle can rehydrate the soil, but avoid overwatering, which encourages fungal development.
If the damage is severe and the turf is completely dead, light topdressing with sand or compost can help smooth the area. This encourages the surrounding Bermuda grass to spread new stolons into the bare spots. Recovery may take several weeks, and continuous monitoring for recurring symptoms is necessary to ensure the treatment was fully successful.
Cultural Practices for a Healthy Lawn
Long-term prevention of brown spots is achieved by optimizing cultural practices, building the turf’s natural resistance to environmental and biological stressors. Mowing Bermuda grass at the correct low height, typically between 0.5 and 1.5 inches, encourages dense, lateral growth. Mowing frequency should be high enough to ensure no more than one-third of the blade height is removed in a single cutting, minimizing scalping stress.
Proper irrigation management is equally important. Bermuda grass performs best with deep, infrequent watering cycles rather than light, daily sprinklings. Supplying about one inch of water per week, applied in the early morning, encourages deep root growth. This also allows the leaf blades to dry out quickly, limiting the period favorable for fungal spore germination.
Strategic fertilization, particularly with nitrogen, strengthens the turf. Applying nitrogen in split applications throughout the peak summer growing season provides the necessary energy for recovery and dense growth. Avoiding heavy nitrogen applications in the spring or fall helps prevent the conditions that favor diseases like Spring Dead Spot and Brown Patch.