A pathosystem is an ecosystem in which parasitism occurs. Parasitism of corn by Colletotrichum graminicola results in anthracnose, an important disease of corn. The disease has three distinct phases: 1. Anthracnose leaf blight that usually occurs between V2 and V12; 2. Anthracnose top dieback that usually occurs from R4 onwards; and 3. Anthracnose stalk rot that is usually prevalent around physiological maturity. Colletotrichum graminicola was not considered an economically important pathogen of corn until the early 1970s. Today it seems like almost every cornfield has plants infected with the pathogen.