Red thread

Symptoms And Signs. The first noticeable symptoms are water-soaked patches of grass in the spring. Infected grass blades soon die and fade to a bleach-tan color when dry. Infected leaf blades are often interspersed with healthy unaffected leaf blades giving the grass a ragged appearance. In severe cases, most leaf blades may be killed and diseased grass looks scorched or yellowed in irregularly-shaped or circular patches from 5 to 50 cm in diameter. The patches may be widely scattered or, if close together, may coalesce into larger spots.
In humid weather, the fungus Laetisaria fuciformis grows visibly on the infected grass blades and leaf sheaths. The fungus produces thread-like strands or web-like areas of coral-pink to blood-red hyphae on the tips of brown grass blades. The strands can protrude up to 2 cm upward from the blade tips and are easily seen, hence the name "red thread disease". 
Disease Cycle. Laetisaria fuciformis may produce spores for dispersal, however, the primary means of dispersal is the spread of infected tissue and bits of the "red thread” (sclerotia) to healthy areas of grass. This type of spread depends upon mowing, foot traffic, and other activities which occur on the diseased turf.
Invasion by the fungus is quick, and leaves may begin to die 2 days after becoming infected. Fungal hyphae and dried pieces of the fragmented "red thread" enable the fungus to survive when conditions are not favorable for disease development (winter, midsummer, etc.). During dry conditions, the "threads" may be viable for up to 2 years.