Red String Disease in Lawns

Identification

• Red thread disease is common to fescue, bentgrass, ryegrass and bluegrass. This fungal disease spreads by spores germinating and releasing. Mowing and foot traffic can spread fungal spores to other areas of the lawn. When temperatures do not favor its germination and spread, red thread fungal spores are able to go dormant for up to two years, according to Cornell University. It is important to diagnose red thread problems to prevent the disease from seriously damaging your yard.

Damage

• Water-soaked patches of grass is the first indicator that your lawn has been infected with red thread, according to Cornell University. Parts of the infected lawn eventually bleach out or turn tan. By closely examining the grass blades, you may notice tiny fungal threads on the tips of brown or dead grass. Left untreated, the grass yellows, turns brown and dies. Grass can die out two days after the initial infection. Small patches can develop into large areas of dead or dying grass if the disease goes unmanaged.

Management

• Keep the soil pH range between 6.5 and 7.0, as recommended by Cornell University. Conduct a soil pH test by digging a 6-inch hole in the yard. Collect soil samples from the bottom of the hole and follow a soil pH test. Spread lime over soil that is too acidic or under 6.5. Sulfur should be spread over soil that is too alkaline or over 7.0. Moreover, fixing your thatch problems may control the disease or help prevent grass from becoming infected in the future. Dethatch your lawn if thatch layer is more than 1/2 inch. A thick thatch layer encourages red thread infection.

Treatment

• Apply a fungicide to severely infected grass. Use a fungicide that contains chlorothalonil, myclobutanil, azoxystrobin or triadimefon, as suggested by Cornell University. To prevent causing more damage, avoid applying the fungicide to water-stressed lawns. Give your lawn a deep watering the morning before the day you apply the fungicide. It is important that grass isn't wet just before cool nighttime temperatures set in. The combination of wet blades and low temperatures encourages fungal diseases. In addition, bag up all grass clippings until the diseases has been eradicated by the fungicide to prevent spreading the disease.