Dead spot is a fairly new disease caused by a fungus, Ophiosphaerella agrostis. The disease appears to be more severe on newly established golf course greens under 4 years of age. Initial symptoms appear as small reddish spots about 1 to 2 cm in diameter. Spots gradually enlarge to a maximum of approximately 6 cm and have a characteristic tan center with a reddish brown margin. Open, exposed areas also appear to be affected more severely. The fungus invades the roots and crowns of susceptible species and affects the plant's ability to transport water. Wilting occurs as a result of severe infection, especially during the heat of the summer. Reproductive structures known as pseudothecia may be found in infected leaf tissues and in dead tissues. These structures are black, flask-shaped, and embedded in the plant tissue. They release spores that cause new infections. Symptoms are more severe in hot and dry weather, but the fungus can remain active until a hard frost.