In the field, it has been observed that the maize is first infected by P. maydis, causing small black stains in the form of exalted carbonaceous scabs, that due to their appearance are denominated asphalt stains .
A nivel de campo, se ha observado que siempre el maíz es primeramente infectado por P. maydis, produciendo pequeñas manchas negras en forma de costras carbonosas sobresalientes, que por su aspecto se les denomina manchas de asfalto .