Gray leaf spot
Area of impact: Leaves
Description: First appears as small yellow or tan spots with halos later developing into gray rectangular lesions up to 4" long by 1⁄8" wide with distinct parallel edges.
Pathogen involved: Cercospora zeae-maydis (a fungus)
Timing/Conditions: Can occur anytime from corn silking to maturity. Prefers moderate to warm temperatures and long periods of wet weather or high humidity.
Contributing factors: Overwinters in corn debris. Susceptible hybrids, corn-on-corn crop rotation and minimum tillage increase the risk of development.
Management practices: Use resistant hybrids, crop rotation, conventional tillage and foliar fungicides.