Bermuda grass (Cynodon dactylon) is a resilient, warm-season turf that requires consistent maintenance to maintain a deep green color. When the turf turns yellow, a condition known as chlorosis, it signals stress from an underlying issue. Diagnosing the cause requires examining the pattern of discoloration, which often points to nutrient deficiencies or improper maintenance. Understanding these symptoms is the first step toward restoring the lawn’s health.
Nutritional Deficiencies
Nitrogen (N) is the most consumed nutrient by Bermuda grass, and a deficiency typically causes a uniform, pale green to yellow color across the entire leaf blade. This yellowing begins on the older, lower leaves first, as mobile nitrogen is redirected to support new growth. To correct this, a regular feeding schedule with a high-nitrogen fertilizer is necessary throughout the growing season.
Iron (Fe) deficiency, or iron chlorosis, presents a different pattern because iron is an immobile nutrient. Symptoms first appear on the newest growth, causing the upper leaves to turn yellow while the veins remain distinctly green (interveinal chlorosis). This condition is often tied to high soil pH, which makes the iron inaccessible to the roots. Applying a chelated iron supplement provides a quick green-up, but long-term correction requires addressing the soil’s pH level.
Water Stress and Drainage Issues
Improper water management is a common reason for Bermuda grass yellowing, as both too little and too much water cause distress. Drought stress from underwatering leads to a temporary blue-gray color before the grass progresses into straw-yellow dormancy. If footprints remain visible after walking across the lawn, the grass lacks sufficient moisture needed to spring back.
Overwatering or poor drainage also causes yellowing because saturated soil deprives the roots of essential oxygen. This lack of aeration starves the root system, leading to root suffocation and chlorosis, often resulting in a spongy feel underfoot. To address this, check the soil moisture four to six inches deep and water deeply and infrequently, aiming for about one inch per week. If poor drainage is the issue, aeration or incorporating soil amendments can improve the movement of water and air.
Pests and Fungal Diseases
Biological stressors can cause patterned yellowing that is distinct from uniform nutrient or water issues. Fungal diseases often thrive in humid conditions, manifesting as localized spots or patches of discolored grass. Rust, for example, appears as yellow or orange powdery pustules on the grass blades, which easily rub off onto shoes or clothing.
Dollar Spot is another common fungus, identifiable by small, sunken, circular patches of yellow or straw-colored turf. Insect pests also cause damage, such as grubs that feed on the roots, leading to large, irregular patches of yellow or brown turf that can be easily pulled back (the “tug test”). Bermudagrass mites are microscopic arachnids that inject toxic saliva into the plant, resulting in a “witches’ broom” appearance, where the grass terminals become tufted and severely stunted before turning yellow. Initial management for most fungal issues involves improving air circulation and adjusting irrigation practices, while severe infestations may require a targeted fungicide or insecticide application.
Correcting Cultural Practices
Sometimes the cause of yellowing is a direct result of the homeowner’s routine care, categorized as mechanical or chemical damage. Cutting Bermuda grass too low, known as scalping, removes too much of the green leaf tissue and exposes the pale yellow stolons beneath. To prevent this mechanical stress, maintain a mowing height between one and two inches, never removing more than one-third of the blade height in a single mowing.
Chemical burn is another common issue, caused by the over-application of granular fertilizer or improper use of herbicides. Excessive nitrogen salts from fertilizer can draw moisture out of the grass blades, resulting in scorched, yellow-tipped, or brown patches. Applying weed killers during high temperatures or at incorrect concentrations can also cause the grass to turn yellow or white. Finally, a brief, overall yellowing may occur during seasonal transition when the grass is coming out of its winter dormancy. Following manufacturer instructions precisely for all chemical applications and calibrating spreaders helps prevent these forms of damage.