Bentgrass dead spot

On creeping bentgrass grown on golf course putting greens, dead spot initially appears as small, reddish brown or copper-colored spots approximately 1.0 cm in diameter, which may increase to about 8 to 10 cm in diameter. Initial O. agrostis infection centers can be confused with other turfgrass diseases such as dollar spot (Sclerotinia homoeocarpa), copper spot (Gloeocercospora sorghi), and Microdochium patch (Microdochium nivale). Spots also can mimic damage from black cutworms or the impact of golf balls, which commonly are found on putting greens. As the disease progresses, grass in the center of the spots becomes tan, while leaves in the periphery of expanding patches appear reddish brown. O. agrostis was isolated from bentgrass and bermudagrass leaves, roots, crowns, and stolons, demonstrating that O. agrostis colonizes all plant tissues. Dark brown to black ectotrophic hyphal masses can be found near or on the nodes of creeping bentgrass stolons, but generally are lacking in the internode region of stolons. In bermudagrass, hyphae generally are found within roots and stolons, and only occasionally are found growing ectotrophically.