Gibberella stalk rot
Symptoms are similar to Fusarium stalk rot. A distinguishing characteristic is the pink to reddish discoloration that occurs inside the stalk. The disease is favored by warm wet conditions, especially in continuous cropped corn with high levels of residue. The disease also affects wheat where it can cause scab and seedling blight. Same as for Fusarium stalk rot.
Taken from Corn Production Handbook, KSU Extension
Pest photo source
Diagnosing Corn Problems in Kansas, KSU Extension