Brown patches disrupt the uniform green appearance of a lawn, often signaling a deeper problem than simple drought. These areas of dead or dying turf are a common symptom resulting from various issues affecting grass health. Successful lawn repair begins with systematic diagnosis, involving careful observation of the damage’s size, shape, and location. Understanding that these patches are the visible result of unseen stress—whether from poor maintenance, insects, or fungal disease—is the first step toward restoring the lawn’s health.
Cultural Practices and Environmental Stress
The most frequent causes of brown patches relate to how a lawn is maintained, creating a stressed environment where the grass cannot thrive. Improper watering is a primary culprit, as both underwatering and overwatering lead to dehydration or root damage. Watering too frequently and lightly encourages shallow root growth, making the grass susceptible to heat stress. Watering in the late evening leaves the grass blades wet overnight, which promotes fungal growth.
Chemical stress is another common non-living cause, often appearing as localized brown spots from fertilizer burn. Granular fertilizers contain salts; when applied too heavily or without sufficient water, the high salt concentration dehydrates the plant. Similar damage occurs from pet urine, which contains high concentrations of nitrogen and salts that create a scorched patch with a dark green ring around the perimeter. Mechanical damage from mowing with a dull blade shreds the grass tips instead of cutting them cleanly, leaving a frayed, brown end that weakens the plant.
Insect Pests and Larval Damage
When maintenance issues are ruled out, brown patches may point toward destructive insect activity. One damaging subsurface pest is the white grub, the C-shaped larval stage of several beetles. Grubs feed voraciously on grass roots, severing the connection between the turf and the soil. This root damage causes irregular patches to turn brown and die; the sod can often be easily lifted because no roots hold it in place.
Another significant pest is the chinch bug, a small, sap-sucking insect that feeds above ground in the thatch layer, thriving in hot, dry conditions. Chinch bugs pierce the grass blades to extract fluids and inject a toxic substance that blocks the plant’s ability to transport water. The resulting damage appears as irregular, spreading patches of dead, straw-colored grass that will not recover even after watering, often starting in the hottest areas near pavement. Detecting chinch bugs requires parting the grass near the edge of a brown patch to look for the tiny, dark-bodied insects with white wing markings.
Common Lawn Diseases
Fungal pathogens frequently cause brown patches, especially when environmental conditions favor their growth, such as high humidity and warm temperatures. Brown Patch, caused by Rhizoctonia solani, typically affects cool-season grasses during mid-summer when nighttime temperatures remain above 68°F. This disease creates large, circular or irregular patches, often several feet in diameter, which may be surrounded by a characteristic dark, grayish-purple border called a “smoke ring.” The fungus primarily attacks the leaf blades and is exacerbated by excessive nitrogen fertilizer and prolonged leaf wetness.
Another common fungal issue is Dollar Spot, which appears as small, distinct spots roughly the size of a silver dollar, though they can merge into larger patches. The disease is identified by straw-colored lesions with reddish-brown edges on individual grass blades. Unlike Brown Patch, Dollar Spot is associated with low nitrogen fertility and excessive moisture from dew or light, frequent watering. Fine, cobweb-like strands of fungal growth, known as mycelium, may be visible across the spots in the early morning before the dew evaporates.
Remediation and Long-Term Prevention
Once the specific cause of the brown patches is identified, immediate action and long-term changes are necessary for recovery. For areas damaged by grubs or chinch bugs, a targeted insecticide application is required to eliminate the pest population, followed by reseeding the dead patches. If a fungal disease is confirmed, a fungicide labeled for that specific pathogen should be applied, paired with cultural adjustments to prevent recurrence.
Long-term prevention focuses on improving the lawn’s environment to make it less hospitable to pests and disease. Adjusting the irrigation schedule is paramount, moving to deep, infrequent watering early in the morning so the grass blades dry completely before nightfall. Aeration helps relieve soil compaction, allowing water and nutrients to penetrate the root zone more effectively. Maintaining a moderate fertilization program and avoiding high-nitrogen applications during hot, humid summer months reduces the grass’s susceptibility to diseases.