This disease is often mistaken for contact herbicide injury because of the appearance of spots. It usually appears on lower leaves following wet weather. This disease also is prevalent in Illinois and Indiana this year. Anthracnose , caused by the fungus Colletotrichum graminicola , has become a familiar disease in Iowa and is usually the first leaf disease to appear. Sometimes a yellowed zone can be seen outside the dark border.
Spots often appear along the leaf margin and can grow together, causing the entire leaf to wither.
The fungus produces its spores on these spots, and the spots also contain tiny black spines that can be seen with a hand lens. Both diseases probably will not cause economic damage, especially with drier weather. Holcus leaf spot rarely persists through mid-season and no control measures are warranted. Anthracnose leaf blight can cause yield loss if it persists and moves up the plant, which seems unlikely at this point. Other mid-season leaf diseases also will be appearing soon, or have already been observed.