Area of impact: Leaves

Description: Oval watery lesions appear first, enlarging up to 15 mm long. Lesions are tan with reddish-brown borders, and they appear on lower leaves early in the season and upper leaves late in the season.

Pathogen involved: Colletotrichum graminicola (a fungus)

Timing/Conditions: Occurs at seedling phase and at full maturity—but not usually in the middle of summer—after high temperatures and long periods of wet weather.

Contributing factors: The fungus overwinters on corn debris.

Management practices: Use resistant hybrids, tillage (where appropriate) and crop rotation.