Fungal Diseases in Grasses

Anthracnose

• Anthracnose is a fungal disease that often affects turfgrass. Annual bluegrass and bentgrass are commonly affected by this disease. Anthracnose develops in the summer, when temperatures are high, but it also occurs during the spring and fall months. According to the Missouri Botanical Garden, the symptoms most commonly associated with anthracnose in grass include scattered patches of dead grass and the development of black fungal strands on grass blades. Grass infected with anthracnose often has a bronzed or yellow appearance and wilts quickly during the hot part of the day. Anthracnose often causes grass to require more watering than healthy grass. Wet, humid weather places stressed grass at an increased risk of developing anthracnose.

Pythium Blight

• All types of turfgrasses are at risk of developing a fungal disease known as pythium blight, which is also known as grease spot. Hot, humid weather conditions are favorable for the development of this fungal disease, making it most common in the summer months. Pythium blight is characterized by the small patches of blighted grass. These patches occur during warm, rainy periods and grass takes on a greasy, water-soaked appearance. Progression of the disease leads to fading of the grass within the patches, until the grass is light brown in color, states the Missouri Botanical Garden. Small patches of blighted grass often merge to form large areas of dead grass. Applying fungicides approved for use with pythium blight may prevent worsening of symptoms. Repeated fungicide applications are often necessary to control this fungal disease.

Red Thread

• Red thread is a disease caused by the fungus Laetisaria fuciformis. Certain types of grass such as fescue and ryegrass are more commonly affected by red thread, which occurs primarily in cool, humid weather conditions. According to North Dakota State University, the earliest symptom of red thread is greasy, water-soaked patches of grass, which later turn white or tan. Affected areas of grass often have pink, slimy fungus growing on grass. This pink fungus forms strands of bright red near the tips of grass, which is where the disease got its name. Red thread is not affected by the use of fungicides. Avoid overwatering grass with this fungal disease, and apply a fertilizer to help the lawn recover.