Anthracnose leaf blight

Tan, irregular shaped lesions appear on lower leaves as early as V3 to V4. Lesions may reach ½ inch in length with a red, reddish brown, or yellow orange border. Anthracnose is most common in fields with old corn debris present. High temperatures and cloudy, rainy weather favor infection. Resistant hybrids. Caution: resistance to leaf blight is not correlated to resistance to the stalk rot phase of the disease. Rotation or tillage to eliminate crop debris.

Taken from Corn Production Handbook, KSU Extension