A patchy lawn with bare spots signals an underlying issue with turf health. These areas of exposed soil are rarely random and can almost always be attributed to a few distinct causes that damage the grass roots or blades. Identifying the specific pattern and nature of the damage is the first step toward successful repair and prevention. A closer look at the location, size, and appearance of the spots can reveal whether the culprit is a living organism, a chronic soil problem, or a sudden external injury.
Damage Caused by Insects and Pests
Subsurface pests like grubs frequently cause bare spots by destroying the grass’s root system. Grubs are the larvae of beetles, such as the Japanese beetle or European chafer, and they feed on the roots just beneath the soil line. This root loss causes the grass to wilt and turn brown in irregular patches, making the turf easy to lift or roll back like a loose carpet since it is no longer anchored.
Surface-feeding insects, such as chinch bugs, cause damage differently by attacking the grass blades themselves. These tiny insects pierce the grass stalk and suck out the plant’s fluids while injecting a toxin that prevents water and nutrient absorption. The resulting damage often appears as irregular, spreading yellow or brown patches, typically starting in the hottest, sunniest areas of the lawn. Indirect pest damage can also occur when animals like skunks, raccoons, or birds dig into the turf to feed on the concentrated population of grubs beneath the surface.
Bare Spots Due to Fungal Diseases
Fungi can also create bare spots, often triggered by environmental conditions like prolonged leaf wetness or high humidity. Brown Patch, caused by the fungus Rhizoctonia solani, typically forms roughly circular patches that can range from six inches to several feet in diameter. The grass blades within the patch turn light brown, and the outside edges may display a dark, smoky ring where the disease is actively spreading.
Another common pathogen is the fungus responsible for Dollar Spot, which produces distinct, small circular spots about the size of a silver dollar. This disease is often associated with lawns that are low in nitrogen and is exacerbated by cool nights with heavy dew. Unlike grubs that attack the roots, or chinch bugs that target the blades, these fungi primarily attack the leaf tissue and crown of the plant.
Soil Quality and Environmental Stressors
Chronic issues related to soil structure or available light cause thinning turf that eventually leads to bare areas. Grass requires at least six hours of direct sunlight per day for optimal photosynthesis, and placing a sun-loving variety like Bermudagrass in a shaded area will cause it to weaken and thin out. Conversely, shade-tolerant grasses like Fine Fescue or St. Augustine are better suited for areas under trees or near structures, thriving on as little as four hours of sunlight daily.
Soil compaction occurs where soil particles are pressed tightly together, reducing the pore space needed for air and water. This lack of oxygen and water penetration starves the roots, leading to weak, sparse growth and eventual die-off, especially in high-traffic zones. Correcting soil chemistry is also a factor, as an imbalanced soil pH (too acidic or too alkaline) limits the grass plant’s ability to absorb necessary nutrients.
Acute Physical and Chemical Injuries
Sudden, localized bare spots are usually the result of a concentrated external trauma or chemical exposure. Pet urine is a frequent culprit, which creates a distinct circular burn patch due to its high concentration of nitrogen and salts. This localized overdose of nitrogen causes the grass to die in the center, often leaving a ring of unusually dark green, healthy grass around the perimeter.
Excessive friction or foot traffic, particularly on wet soil, can quickly wear down the grass blades and compact the soil beneath, leading to defined pathways of exposed dirt. Accidental chemical burns from spills like gasoline, oil, or overlapping applications of granular fertilizer can cause immediate turf death. Salt runoff from winter de-icing activities or from water softeners can also accumulate and dehydrate the grass, resulting in bare spots with sharp, defined edges.