Brown spots in an otherwise green lawn stand out and look unattractive. They range in size from several inches wide to several feet. These spots adversely affect the health of a lawn, which is why they require immediate repair. There are several reasons why brown spots occur in a lawn and identifying them is critical for proper control and repair. Some reasons for these unsightly brown spots or patches include foot traffic, dog urine, overfertilization, overwatering, thatch buildup and fungal disease.
Apply a fungicide containing benomly, sulfur or chlorothalonil over the area affected by brown patch disease. Also called summer patch, this disease causes brown spots with a 4 to 10-foot-diameter and yellow edges. Follow the label direction for applying the fungicide and repeat application five to six days until the brown spot disappears.
Water the area heavily if brown spots occur soon after you fertilize your lawn. Excessive nitrogen in lawn fertilizers causes grass to burn and turn brown, forming spots. Douse the spot with water to wash away accumulated nitrogen in the soil, and always follow manufacturer's directions when fertilizing to feed the grass the right amount.
Rake the brown spot with a thatch rake to remove buildup of thatch. Thatch is a thick layer of accumulated grass clippings, plant debris and leaves that prevents essential nutrients, sunlight, air and water from reaching the soil and roots, thus causing grass to turn brown. Dethatch once every four months so essential components reach the end of grass blades and soil.
Aerate compacted soil under a brown spot with a core aerator. Water cannot penetrate compacted soil, which is why the it is thirsty and the grass directly above it forms a brown spot. A core aerator pulls out core plugs so moisture penetrates the soil.