Red Thread: Pretty Severe at the Moment

Red thread (pathogen: Laetisaria fuciformis) is especially severe at the moment on perennial ryegrass turf and to a lesser extent on Kentucky bluegrass and fine fescue. The relatively cool wet weather we are currently experiencing has been ideal for disease development. 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.

Red 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 or overwatering in the late afternoons or early evenings. If red thread becomes severe, especially in green approaches or short rough around greens, fungicide applications may be warranted.

Authors: Karl Danneberger