What is it?
Red thread, caused by a fungus, is favored by cool, humid weather. Red thread mostly attacks lawns with fescue and ryegrass, and has been found severe in some lawns with bluegrass. Initial symptoms of red thread appear as water soaked lesions on the leaves. The lesions enlarge across the leaf which causes blighting or withering. The color can be tan to light straw color. This results in round patches in the turf approximately 1-2” in diameter. The patches may expand to form irregular shapes up to 18” in diameter.
What are the signs?
Red thread can be easily identified by the observation of pink to yellow to red branched, strands of red hairs extending up to 1/8” above the leaf tips and by pink to red, cottony or fuzzy hairs on the leaf blade, especially under humid conditions.
The best temperature for red thread to develop is 68-75 degrees. It usually occurs from midspring to early summer and in early fall on slow growing turf. A water saturated atmosphere associated with prolonged light rain increases red thread development.
Fertilizing will help the lawn to recover quickly and allow the lawn to grow out of the disease. You don’t want to deprive your soil of nitrogen during this time. A balanced rate of slow release granular fertilizer should be applied regularly. Deep watering in the morning hours and never in the afternoon or evening will help to reduce the damage. Avoid light frequent watering, this will make the disease worse. Collecting the grass clippings while the disease is active will help stop the spread.