After these last few weeks of rainy weather we begin to see large brownish patches in lawns. What you are seeing is called Red Thread Disease. You will see these patches gradually grown out of the turf with regular mowing and the onset of warmer weather. Spring and Fall are notorious for this disease especially with very wet springs!
Red thread is a common disease on turf during cool wet weather in the spring and fall. Turfgrasses affected include tall fescue, fine fescue, rye grass, bentgrass and to a lesser extent Kentucky bluegrass and Bermuda grass.
Primary symptoms: Red thread will produce, under optimum conditions of wet cool weather, a reddish gelatinous fungal growth that can be seen on leaf blades and sheaths. When the leaves dry the fungal growth becomes a paler pink or red and extends from the leaf tips as hard brittle strands. These strands fall into the soil or thatch layer to serve as resting structures for the next infection period. Infected turf has circular to irregularly shaped patches ranging from 2 inches to 3 feet in diameter with a straw-brown or pinkish tan color. Red thread appears most frequently in early spring and fall and occasionally during the summer under prolonged rainy cool periods.
-University of Maryland Extension Service