I thought we would miss this turf disease in 2000 because the weather was initially dry. This fungal disease is commonly associated with cool, damp weather in spring and fall. Recent changes in weather conditions have produced sightings of red thread in central and northern parts of Illinois. The fungus that causes this disease forms conspicuous, coral pink or red threadlike masses on the grass blades and leaf sheaths. In the morning dew, the color is even more evident. As the disease progresses, the blades die from the tip downward. The diseased turf is eventually bleached tan, yellowed, or scorched in circular to irregular patches. These patches may be anywhere from 1 to 2 inches in diameter. Because the dead leaves are generally interspersed with apparently healthy leaves, the turf will appear scorched and ragged. If that is the case, look at the turf in the early morning to confirm or rule out this disease.
Red thread rarely kills turf plants, but it may weaken them and contribute to decline or infection by other diseases or weather stress. The disease is par-ticularly prevalent on slow-growing, nitrogen-deficient turf. It is also favored by excess thatch, low calcium levels in the soil, water stress, a sudden drop in temperature, and misused herbicides. By correcting these stress factors, you will be moving toward control of the disease. Often a fertilization treatment will correct the problem, but red thread may occur even on well-fertilized lawns.
If you have a problem with this disease, put the mower bag back on the mower, and collect the clip-pings. The fungus will remain viable on the clippings, so you want to remove that inoculum from the lawn. Some bluegrass varieties with resistance to the red thread fungus are listed in RPD No. 413. Check with your local seed source for availability of other sources of resistance, and rake and reseed now if your lawn is severely affected. Chemical options are not the usual avenue of red thread control.