RED THREAD

• Pathogen: Laetisaria fuciformis (syn. Corticium fuciforme)
• Grasses Affected: Annual bluegrass (Poa Annua), creeping bent grass (Agrostis palustris), hard fescue (Festuca ovina var. duriuscula), bermuda grass (Cynodon dactylon) Kentucky bluegrass (Poa pratensis), red fescue (Festuca rubra), sheep fescue )Festuca ovina), tall fescue (Festuca arundinacea), annual ryegrass (Lolium multiflorum), perennial ryegrass (Lolium perenne).
• Season of Occurrence:  Outbreaks of this disease commonly occur in late winter and early spring.  However, during extended periods of rainfall and night temperatures in the high 60s to low 70s°F (19-22°C), Corticium red thread can also cause severe damage to turf grass during the summer months.
• Symptoms and Signs:  In overall view, Corticium red thread is seen as irregularly shaped patches of blighted turf grass, ranging in size from 2 inches (5 cm) to 3 feet (0.9 m) in diameter.  In cases of involvement of large areas of grass, the patches often have an overall “ragged” appearance due to a mixture of diseased and unaffected leaves.  The disease is confined to the leaves and leaf sheaths only.  Small, water-soaked spots develop within 24-48 hours from the time of infection.  Under favorable weather conditions, the affected leaves may be completely covered with the pink gelatinous growth of the pathogen.  A key feature for field diagnosis of Corticium red thread on tall cut grass is the presence of fine, threadlike, coral pink structures (Sclerotia) 1/16-1/4 inch (1-6 mm) in length at the terminal portions of the leaves.  Under the close mowing conditions of golf and bowling greens and golf tees, the affected areas range from 2-6 inches (5-15 cm) in diameter and are irregular in outline.  Close examination of leaves from the affected areas will usually reveal the presence of a light reddish tinge to the sheaths.  Also, although their numbers will be low because of the close mowing, the “red threads” that characterize this disease on tall cut grass can also be found in these areas.
• Conditions Favoring Disease Development:  The Corticium red thread pathogen is dispersed to new locations within a stand of turf grass by diseased leaf tissue adhering to the surfaces of maintenance equipment.  Although air temperatures in the 65-75°F (18-24°C) range are usually considered most conducive to the development of the disease, the length of time the surfaces of the leaves are wet appears to be an overriding factor in its development.  Corticium red thread can develop on unfrozen turf under snow cover and during winter months that are marked by extended periods of rainfall.  Also, major outbreaks of the disease can occur in warm summer months during prolonged rainfall.  Increased potassium fertilization has been shown to reduce the severity of the disease.  nitrogen nutrition does not lessen the susceptibility of turf grass to Corticium red thread.  However, application of nitrogenous fertilizers often reduces the severity of field symptoms of the disease.  this is probably the result of more rapid plant recovery during periods of decreased activity on the party of the pathogen.