Identify and Treat Fungal Disease in Your Lawn

In addition to drought and summer stress, fungal diseases are a big source of ugly, brown or diseased-looking patches that mar the beauty of your otherwise perfect lawn. If you have cooler season grass, your lawn is more at risk for disease when the weather is excessively warm. It’s the exact opposite if you have warmer season grass, then cooler weather is a danger.

Other conditions to be on the lookout for are extra dry or extra wet weather, as well as overcast, cloudy days. The latter reduces your lawn’s ability to dry out well enough, which means the dew is less likely to evaporate. The overly moist conditions are perfect for disease. Humidity and your lawn just don’t work well.

We’ve compiled a quick “Who’s Who” of fungal lawn diseases to help you maintain your lawn, including the grass types affected, season it occurs and signs to look for:

Anthracnose Lawn Disease

Turfgrass, mainly centipede & bluegrass. Summer & fall. Various sizes of brown, tan or reddish-brown patches; spot may appear on grass blades. Kills turfgrass if not treated.

Brown Patch - Lawn Diseases

Brown Patch

Zoysia, bentgrass, ryegrass, centipede, St. Augustine, bluegrass and fescue. Spring & fall. Large or small circles of dead grass, the perimeter of which may have a smoky color. Areas of lawn may appear sunken. Affected leaves can be plucked from the stems.

Dollar Spot

Dollar spot

Bermudagrass, ryegrass, bentgrass, bluegrass and fescue. Late spring, summer & fall. Silver dollar-sized patches of brown or tan grass that may merge. Does not usually leave permanent damage.

Fairy Ring

Fairy ring

Turfgrass, all year. Dark green circle or semi-circles appear in lawn. Surrounding area may have a lighter-color and die & there may be mushrooms. All affected areas must be dug up and reseeded.

Fusarium Blight

Fusarium blight

Bluegrass. Occurs in hot, dry weather. Lawn color changes from light green to brown to tan before your lawn dies.

Fusarium Patch

Fusarium patch/snow mold

Zoysia & cool-season grasses. Fall, winter & spring typically after snow melts. Also any cold, wet weather. Appears greenish yellow before becoming pink. If gray, it’s a different snow mold that starts yellow and ends up grayish white.

Leaf Spot

Leaf spot

Turfgrasses. Spring, summer & fall. Grass becomes tan, brown or gray with purple, tan or red spots. If not treated, kills or severely thins your lawn.

Necrotic Ring Spot

Necrotic ring spot/summer patch

Bermudagrass, fescue, bentgrass & bluegrass. Spring, summer & fall. Circular, sunken patches of reddish-tan grass resembling a bull’s eye. May also have an irregular or oval shape.

Powdery Midlew

Powdery mildew

Bermudagrass, zoysia & bluegrass. Spring, summer & fall, common in shaded areas. Looks like white dust; grass turns tan, then brown. Damage may be permanent.

Pythium Blight

Pythium blight

Turfgrass. Spring, summer & fall. Creates brown, slimy areas, which earn it the nickname grease spot. May also show white patches. Spreads and kills quickly.

Red Thread Lawn Disease

Red thread

Bluegrass, fescue, bentgrass & ryegrass. Spring & fall. Look for faded or red areas with pink or reddish threads going from leaf tip to leaf tip. Doesn’t usually leave permanent damage.

Rust on Lawns


St. Augustine, ryegrass, Bermudagrass & bluegrass. Summer & fall. Appears orange and rusty. Spores spread easily by clinging to clothing and tools. Not usually harmful.

You can stop fungal diseases from spreading by removing grass clippings from affected areas. Don’t walk through the affected area. Clean all tools you use in the affected area before using on healthy parts of your lawn.

Fungicides also stop the spread. It’s important to get one that’s specifically made for your lawn’s disease. Follow all manufacturer’s instructions. Two well-known choices are Immunox Multi-Purpose Fungicide Spray and Bayer Fungus Control for Lawns.

An Ounce of Prevention…

You can work to prevent fungal disease by doing the following:

  • Build up low spots as water collects there and invites disease.
  • Level off high spots and improve overall drainage.
  • Plant disease-resistant turfgrass that is for your region.
  • Test soil every 3-5 years & follow the test recommendations.
  • Use the correct fertilizing schedule. (will link to fertilizer schedule)
  • Maintain the proper height for your grass type by mowing regularly. Sharp blades prevent ragged cuts.
  • Don’t mow wet grass.
  • Avoid creating a grain by changing your mowing pattern each time.
  • Give your lawn more oxygen, water and nutrients by aerating it. This also fixes soil compaction.
  • Help increase air circulation or sunlight availability by thinning shrubs and trees. Do not top them, though.
  • Plant a shade-loving turfgrass in shady areas.
  • Remove all debris, including leaves. Debris invites disease and pest infestations.
  • When thatch is over 1/2 inch thick, remove it.
  • Following local water restrictions, water deeply but less often to encourage deeper root systems.
  • Water in the early morning. This allows excess water to evaporate during the day.
  • Stay vigilant. Early detection often prevents damage.