Red Thread

Causal Agent:

Laetisaria fuciformis

Susceptible Turfgrasses:

Creeping red fescue; Perennial ryegrass ; Tall fescue

Symptoms:

Red thread blights in distinct spots or circular patches, which appear pink or reddish-colored and range from 2" to 3' in diameter. When active in the presence of dew or even melting snow, a bright pink to red gelatinous fungal growth can be observed on leaves and sheaths. Resting bodies (i.e., sclerotia) called "red threads" are invariably present. Red threads initially are gelatinous, but soon become bright red, hard and brittle. Blighted leaves eventually turn tan, but on close inspection red threads can be seen embedded in dead tissues. White to pink "cotton candy-like" fungal flocks occasionally develop within blighted canopies.

Conditions Favoring Disease:

Red thread can develop almost any time of the year including at snow melt and in summer, but is most common during extended, overcast and rainy weather in spring. While red thread is widely reported to be most severe in poorly nourished turf, it can severely blight professionally managed turf fertilized with more than adequate nitrogen. Red thread can cause severe thinning and promote weed invasion, but turf normally recovers with adequate nitrogen fertilization.

Management Tips:

• Maintain proper nitrogen and potassium fertility.
• Apply small amounts (~ 0.25 – 0.5 lbs. N/1,000 ft²) of water-soluble nitrogen to blighted areas to promote recovery.
• Blighting often reduces density when crabgrass and other weeds are germinating in spring and a preemergence herbicide should be used where the disease is common.
• Increase air circulation, improve water drainage and reduce shade.
• Preventive fungicide applications during cool, wet weather are highly effective. Curative applications quickly halt disease activity but turf recovery may be slow if weather and/or fertility levels are not conducive.

Frequently occurs in:

In all areas where susceptible cool-season grasses are grown.