Common Lawn Diseases
Learn about how to control the most common lawn diseases.
Thumbnail
Anthracnose
Reddish-brown spots on leaves • blighted areas of lawn can vary in size from 2 inches to 10 feet.

Favorable Conditions1

Warm to hot weather (75 to 95 degrees) • high humidity • excess rain. Over-fertilizing and heavy thatch also encourage disease.

Thumbnail
Brown Patch
Leaves and stems die out in large, circular patches in lawn • one of the most common fungus diseases of fescue lawns.

Favorable Conditions1

Warm to hot weather (75 to 95 degrees) • high humidity • excess rain. Overfertilizing and heavy thatch also encourage disease.

Thumbnail
Copper Spot2
Grass blades develop small red spots that enlarge and become darker red • grass is infested in small, circular patches 1 to 3 inches wide • grass within the spots dies • can look like Dollar Spot.

Favorable Conditions1

Mild to warm temperatures (70 to 80 degrees); high humidity. Over-fertilizing and heavy thatch also encourage disease.

Thumbnail
Dollar Spot
Grass dies in small, circular spots 4 to 12 inches wide • spots may fuse together in big blotches.

Favorable Conditions1

Mild to warm weather (60 to 85 degrees) • excess moisture • under-fertilization. Over-fertilizing and heavy thatch also encourage disease.

Thumbnail
Powdery Mildew2
White to light gray moldy-looking growth on grass blades

Favorable Conditions1 Mild temperatures (65 degrees) • damp weather and excess moisture • shady areas. Overfertilizing and heavy thatch also encourage disease.

Thumbnail
Red Thread
Tan to bleached-looking grass blades that shrivel from the tips • small patches of dead grass • in wet weather you may see small pink thread in the grass.

Favorable Conditions1

Mild temperatures (60 to 75 degrees) • high humidity • misty weather • under-fertilization. Over-fertilizing and heavy thatch also encourage disease.

Thumbnail
Rust
Dust-like orange-colored spores cover grass blades • affected areas of lawn have a rusty look • doesn't usually hurt the grass, but is a nuisance.

Favorable Conditions1

Mild temperatures (60 to 75 degrees) • dry weather or conditions that favor the slow growth of grass. Overfertilizing and heavy thatch also encourage disease.

Thumbnail
Stripe Smut2
Grass blades turn pale green and are stunted • spores form long black stripes on grass blades • grass blades curl and die

Favorable Conditions1

Cool temperatures (50 to 60 degrees) • excess moisture. Over-fertilizing and heavy thatch also encourage disease.

Thumbnail
Summer Patch, a.k.a Frog Disease
Grass forms light green patches up to 24 inches wide that later turn a reddish brown • some patches may have circle of green grass in center

Favorable Conditions1

Warm temperatures (80 to 95 degrees) • high humidity • drought-stressed grass Overfertilizing and heavy thatch also encourage disease.

  1. Overfertilizing and heavy thatch also encourage disease.
  2. Reprinted with permission from the American Phytopathological Society, St. Paul, MN.

Related Articles