Bermuda grass is a popular, warm-season turfgrass known for its fine texture, deep green color, and resilience in high temperatures. This aggressive, fast-growing grass forms a dense lawn when properly maintained, making it a favorite in southern and transition-zone climates. Even this hardy turf is susceptible to developing brown spots, frustrating homeowners seeking a uniform, lush carpet of grass. Identifying the exact cause of these patches is the first step in returning a lawn to its healthy state. The problem can range from fungal infections to improper irrigation or insect activity.
Fungal Pathogens and Disease Control
Fungal diseases are a common biological threat, often triggered by high humidity and prolonged leaf wetness. Brown Patch, caused by the fungus Rhizoctonia solani, manifests as roughly circular, brown or yellow-orange patches ranging from a few inches to several feet in diameter. A distinct, grayish-black “smoke ring” may be visible around the patch perimeter in the early morning when conditions are favorable for fungal growth. This disease thrives in warm, wet conditions, particularly when nighttime temperatures remain above 65°F and the grass has been over-fertilized with nitrogen.
Dollar Spot appears as small, silver dollar-sized spots that may merge into larger, irregular patches. A key diagnostic feature is the presence of tan-colored lesions with reddish-brown borders across the width of the individual grass blades. Dollar Spot often indicates low nitrogen levels and prolonged periods of moisture on the leaf surface.
Managing these diseases involves modifying the environment to reduce the fungus’s ability to flourish. Adjusting irrigation to water only in the early morning allows the grass blades to dry completely before nightfall, significantly reducing leaf wetness. For active infections, a curative application of a broad-spectrum fungicide is required. Effective active ingredients include Propiconazole and Azoxystrobin, which should be applied according to the manufacturer’s instructions.
Avoiding high-nitrogen fertilizers during periods of high heat and humidity helps prevent Brown Patch. For Dollar Spot, ensuring the lawn receives adequate nitrogen through a balanced fertilization program can help the turf grow out of the infection. Systemic fungicides, which are absorbed by the grass, offer longer-lasting protection than contact fungicides. Both types require careful rotation to prevent the fungus from developing resistance.
Fixing Irrigation Errors and Soil Issues
Brown spots are often caused by poor water management or underlying soil structural problems rather than a living organism. Bermudagrass requires deep, infrequent watering to encourage a strong root system. Applying 1 to 1.5 inches of water per week, delivered in two to three sessions, is sufficient for this drought-tolerant species. Shallow, frequent watering encourages weak, surface-level roots that are susceptible to heat and drought stress, leading to browning.
A lawn suffering from underwatering often displays a blue-gray tint and retains footprints that do not spring back immediately. Conversely, overwatering leads to saturated soil conditions, starving the roots of necessary oxygen and causing the grass to turn brown. Excessive moisture also contributes to fungal diseases.
Poor soil structure, specifically compaction, restricts root growth and prevents water and nutrients from infiltrating the soil. The simple screwdriver test can reveal compaction; if a screwdriver cannot be easily inserted past two to three inches, the soil is too dense. Core aeration involves physically removing small plugs of soil, which immediately improves air and water penetration.
Thatch is a dense layer of organic matter between the grass blades and the soil surface. A layer thicker than a half-inch prevents water and fertilizer from reaching the roots, causing the grass to brown. Dethatching or verticutting should be considered during the active growing season to break up this barrier and restore direct soil-to-root contact.
Identifying and Eliminating Insect Activity
Certain insect pests chew on grass blades or feed directly on the roots, leading to localized brown spots. Grubs, the larvae of various beetles, cause damage by feeding on the root system. This results in patches of grass that roll back like a loose carpet when pulled, due to the severed roots. This “tug test” confirms a grub infestation.
Armyworms and sod webworms are caterpillars that feed on the grass blades, leaving ragged, chewed edges and small, irregular brown areas. Sod webworms are often identified by small, white-to-brown moths that flutter up from the turf when walked upon. A soap flush test, where a mixture of dish soap and water is poured over a small area, forces webworm and armyworm larvae to the surface for identification.
Once an infestation is confirmed, a targeted insecticide application is necessary to stop the damage. Curative applications of products containing active ingredients like Chlorantraniliprole effectively eliminate these pests. Treatment should occur when the insects are actively feeding, and all label instructions must be followed to ensure effective control.
Chemical Injury
Brown spots can also result from non-biological chemical injury, such as a localized fertilizer burn or a petroleum spill. Over-application of fertilizer, especially high-nitrogen types, desiccates the grass blades, causing them to yellow and turn brown. If a granular fertilizer spill occurs, the material must be immediately swept up or vacuumed before it is watered in. If the burn has already begun, the area should be flushed generously with water to dilute the concentrated salts and leach them out of the root zone.
Spills from gasoline or motor oil kill the turf and contaminate the soil with hydrocarbons. Immediate action involves drenching the area with water to dilute the contaminant. For severe spills, the contaminated soil should be physically removed to a depth of several inches and replaced with fresh topsoil. Bermuda grass is a vigorous spreader and will eventually fill in the damaged area, but removing the toxic soil is necessary for recovery.
Cultural Practices for Long-Term Lawn Health
Maintaining proper cultural practices makes turf more resilient to environmental stress and pest pressure. Bermuda grass thrives when mowed frequently and kept low, typically between one and two inches. Mowing every three to five days during the peak growing season, and never removing more than one-third of the blade height, encourages lateral growth and density. A sharp mower blade is necessary to ensure a clean cut, as dull blades tear the grass, creating entry points for fungal pathogens.
A consistent fertilization schedule supports grass health without encouraging disease. Bermudagrass requires a high amount of nitrogen during its active growing season, often following a 3-1-2 NPK ratio. Applying between two and four pounds of actual nitrogen per 1,000 square feet annually, spread across multiple applications in late spring and summer, provides the necessary fuel for growth.
Applying nutrients should follow the results of a soil test, which identifies deficiencies or excesses that may predispose the lawn to problems. Adjusting the irrigation schedule to water deeply and infrequently, combined with annual aeration, creates an environment where grass roots can thrive. These routine maintenance practices minimize susceptibility to brown spots.