The following question was sent to the P&PDL diagnosticians here at Purdue University:
Question: Could you please discuss red thread and how to get rid of it?
Answer: Red thread first appears as small (quarter to golf ball size) spots in the turf. These spots are initially purplish-blue or water soaked and eventually dry out to a tan color. Upon closer observation, a distinctive red to coral colored "thread" is often seen growing from tips of infected leaves. This thread is the body or mycelium of the fungus and serves to spread the fungus. This disease is most common on poorly fertilized, slow-growing turf with prolonged periods of rain, high humidity, and temperatures between 65 and 75 degrees. Control of red thread is primarily accomplished through proper fertilization to maintain consistent but not excessive growth. In addition to fertilizer applications made in September and November, apply 0.75-1.0 lb N/1000 sq. ft. in late May using primarily slow release fertilizer. Slow release sources include sulfur- or polymer-coated urea, urea formaldehyde, methylenediurea, dimethylenetriurea or natural organic nitrogen. Perennial ryegrass is especially susceptible.