One of the more common late spring to early summer diseases on cool-season grasses is Red Thread lawn disease. It is most severe on Kentucky Bluegrass, Perennial Ryegrass and Tall Fescue. There is another lawn disease that occurs at the same time and under the same environmental conditions known as Pink Patch.
The main difference between the two lawn diseases are the fruiting structures. Red Thread takes its name from the red thread-like structures called sclerotia that are produced by the fungus. Pink Patch produces tiny puffs of pink-cottony mycelium that resemble little bits of cotton candy stuck to the grass blades. Of the two diseases, Red Thread is the more common one seen in home lawns. Red Thread may develop when temperatures range from 40 to 75°F. Most grass activity occurs when temperatures range 65 to 75°F and during periods of cool, cloudy weather with long periods of evening dew.
What Does Red Thread Lawn Disease Look Like?
Symptoms are often visible from the street as circular patches of tan or pink grass about 4-8 inches in diameter. Upon closer inspection, the sclerotia are easily visible, appearing like small, red threads protruding out of the grass blades, especially near the tip. Red Thread will affect the leaves, leaf sheaths and stems without killing the entire plant, unless the outbreak is severe. The infection begins as small blighted areas on leaves and rapidly enlarge, covering the entire leaf blade. The affected leaves will dry out and turn a bleached straw color.
After it has completed its life cycle, the disease produces the red threads or sclerotia. In other words, unless the weather conditions last a long time, the red threads signal the end of its activity. These threads will break off and act as “seeds” for future outbreaks of the disease. Mowing infected areas has little impact on spreading the disease so collecting clippings during this period is not very beneficial.
How To Treat Red Thread Lawn Disease
It is important to maintain an adequate nitrogen fertility program to lessen the effects of Red Thread. Fertilization after an outbreak of Red Thread will help the turf to “grow out” of the effects of the disease activity. Fertilizer will help the lawn grow and then the diseased parts of the plant can be mowed off to allow newer, healthy blades to grow. Avoid excessive watering during cool, cloudy periods that may extend the time the turf remains wet. Core aeration and overseeding with improved varieties of turf grasses that are more resistant to Red Thread are another two important cultural practices.
There are chemical control options, but by the time the red threads are seen, it is usually too late to apply a preventative disease control application. Making sure the lawn is well fertilized, mowed properly and receives the right amount of water on a weekly basis is the best approach to take when dealing with Red Thread lawn disease.
If Red Thread is a problem in your lawn, contact your neighborhood lawn care professional at Spring-Green. They will be happy to inspect your yard and provide a beneficial lawn care program.