The wet Midwestern spring has resulted in an extraordinary amount of red thread and pink patch in residential turf. While average daily temperature remained normal, or slightly below, the number of days with measurable precipitation has exceeded the norm, resulting in more disease outbreaks. Symptoms create an undesirable appearance, but crowns and roots are not infected, so plants will not be killed and turf eventually will recover. Pink patch and red thread have similar symptoms and are caused by closely related fungal pathogens.
See also: Red Thread
From a distance, red thread symptoms appear as circular patches of tan or pink turf about 4-8 inches in diameter. For both diseases, a pink mycelium colonizes leaf blades.
Red thread is easily distinguished from pink patch by the presence of the antler like structures (sclerotia) growth from blighted leaves.
Red thread most commonly affects fine fescues, turf type tall fescue, perennial ryegrass, and Kentucky bluegrass. Infection can occur over a broad range of temperatures (40-70° F). Symptoms are most often confused with Microdochium blight (pink snow mold) in early spring, and dollar spot in late spring. Although the disease is often associated with malnourished turf, a build-up of inoculum over years can result in outbreaks on well-managed turf, including golf course fairways and tees. The pathogens survive in the turf/thatch as mycelium or weather-resilient sclerotia.
Disease control options
The most important nonchemical (cultural) control option involves sound agronomy and implementing an adequate nitrogen fertility program. This involves reviewing fall-applied nitrogen programs and considering supplemental spring-applied nitrogen on turf with a history of red thread outbreaks. A good fertility program implemented over two to three years should drastically reduce red thread problems in the future.
If the clientele is demanding, fungicides may be used to control both diseases. QoI class fungicides (strobilurins) are very effective, especially when applied before sclerotia form. DMI class fungicides also may be effective. Repeated fungicide applications targeting red thread or pink patch should be unnecessary if turf is fortified with supplemental (0.2 lb N/1000 sq ft) at the time of the initial fungicide application.