Pythium Blight of Turfgrass

Pythium blight is a disease that can occur in the summer.  It commonly affects lawns and golf courses in Iowa when the weather is warm and humid. The fungi that cause these diseases can infect most types of grasses.

Pythium blight starts as small (about 6 inches), circular, reddish brown spots. The disease pattern may occur in streaks following the path that water drains and the path of mowing equipment or foot traffic. Blighted patches can grow to become large, irregular shapes. White cottony fungal threads (mycelium) form on infected blades early in the morning. Infected plants collapse and the diseased areas may become matted and greasy in appearance.

If the temperature drops or the relative humidity lowers, Pythium blight symptoms halt. 

Management Strategies

1. Fill in areas where water puddles.
2. Mow when the grass is dry. Avoid removing more than 1/3 of the blade at one time.
3. Improve air circulation by pruning shrubs and trees.
4. Follow a balanced fertilizer program.
5. Water deeply and infrequently in the early morning hours.
6. Core aerate in the spring or fall to avoid thatch buildup.
7. Preventive fungicide may be used on highly valuable turfgrass. The treatment should be sprayed before the onset of hot, humid weather. Subsequent applications may be required.