Common Lawn Diseases

Anthracnose

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
Products that help
Brown Patch

Brown Patch

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

Favorable Conditions1
Warm to hot weather (75 to 95 degrees) • high humidity • excess rain
Products that help
Copper Spot

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
Products that help
Dollar Spot

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 • underfertilization
Products that help
Powdery Mildew

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
Products that help
Red Thread

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 • underfertilization
Products that help
Rust

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
Products that help
Stripe Smut

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
Products that help
Summer Patch "Frog-Eye" Disease

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
Products that help

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