Background:
Gray leaf spot is caused by the fungus Cercospora zeae-maydis and occurs every growing season. If conditions are favorable for the disease, yield loss can occur. This disease can first appear on lower leaves about two to three weeks before tasseling. Lesions are up to 2 inches long, narrow, rectangular and light tan in color. Later in the disease life, the lesions will turn gray and eventually kill the entire leaf.
Life Cycle:
Gray leaf spot survives in corn residue and is most effective in corn-on-corn fields. Spores are dispersed by the wind and splashing water. Development of this disease favors warm, humid weather (80°F-89°F at more than 90% humidity for 12+ hours). The severity of gray leaf spot depends on environmental conditions and hybrid susceptibility.
Scouting:
When looking for a gray leaf spot, look for long, rectangular lesions in the veins. The color of the lesions will be light tan and then turn gray.
Management:
- Plant non-susceptible hybrids.
- Rotate crops.
- Apply foliar fungicides labeled for gray leaf spot.
- Plant non-susceptible hybrids. (Crop Protection Network Gray Leaf Spot)
