The Ohio State University

Home LandscapeNotes Red thread (pathogen: Laetisaria fuciformis) is occurring on Kentucky bluegrass, fine fescue and perennial ryegrass turfs throughout the Midwest. Red thread is most active between the temperatures of 55 to 77 F. The disease may remain active at temperatures as high as 86 F. Disease symptoms are often found on Kentucky bluegrass during the summer and fine fescue in the autumn. On perennial ryegrass however red thread can appear almost anytime during the year. Red thread appears as circular to irregular shaped patches that are straw to pinkish in color. The patches appear as a brownish to tan in color, and overall give the turf a rather "ragged look". Under wet or humid conditions the patches may appear a pinkish red color with red strands (sclerotia) exuding from the leaf blade. In addition, pink cottony balls (small in diameter) may be present, especially on perennial ryegrass.

Read thread is severe on slow growing, nitrogen deficient turf. Cultural control practices include increasing the amount of nitrogen to the turf. This practice is effective on Kentucky bluegrass and to a lesser extent on perennial ryegrass. Keep the mower blade sharp and try to avoid mowing when the turf is moist. Avoid overwatering in the late afternoons or early evenings. Watering at this time will promote disease development. If red thread becomes severe enough fungicide applications may be warranted.

Posted by Karl Danneberger