Red Thread, fungus lawn diseases.
Red thread disease and it’s associated lawn disease Pink Patch (Laetisaria spp) are both turf diseases that like cool, wet spring weather. It likes temperatures in the 60’s and low 70’s with high humidity and in soils with high moisture content. It is an interesting lawn disease because of the red fungal mycelium (strands) that are visible to the naked eye.
The disease develops in circular or irregular patches from 4 inches to 2 feet in diameter. Affected leaves within these patches are tan or bleached-white in color. From a distance, the patches usually have that reddish appearance, due to the presence of thick, red strands of fungal growth emanating from the affected leaves. It is through production of these “red threads” that the fungus spreads to healthy plants and survives unfavorable conditions. Small tufts of pink, fuzzy mycelium may also be present in or around the patches when the leaves are wet or humidity is high. After prolonged periods of disease development, the patches may merge to produce large irregularly shaped areas of damaged turf.
Red thread most commonly affects Kentucky bluegrass, perennial ryegrass, and sometimes tall fescue. Outbreaks usually occur in lower maintenance turf stands such as residential lawns, golf course roughs, and some low budget athletic fields. Red thread development is most common where turfgrass nutrition is poor but that is not always the case. Soils that have little or no topsoil and organic matter and don’t hold nutrients are susceptible to Red Thread and Pink Patch as well.
Generally, only in the worst cases of these two lawn diseases is it necessary to spray fungicides. There would need to be a prolonged period of cool weather to necessitate control products. A few hot, dry days usually will eliminate the symptoms.
Here is a fact sheet from the University of Maryland that explains the disease in more detail – http://hgic.umd.edu/content/documents/TT-24.pdf
Mark Schlossberg is the President of ProLawnPlus in Baltimore, MD. He graduated from the University of Maryland in 1977 with a B.S. in agronomy. He is the President of the Maryland Association of Green Industries, and past president of the Maryland Turfgrass Council.