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Gray Leaf Spot

Gray leaf spot is a foliar disease occurring in warm-to-hot humid areas, especially where minimum tillage is present. Lesions are long and narrow, parallel-sided, and tan-to-gray in color. The fungus overwinters in corn debris, on or near the soil surface.

Growing Degree Days

Growing Degree Days (GDD) are calculated for each 24 hour day and accumulated from the time the hybrid is planted until it reaches physiological maturity (about 35%) in the fall. The formula used to calculate GDDs is:

T. Max + T. Min. / 2 - 50 = GDD

T. Max. is the maximum temperature during the day and T. Min. is the minimum. Fifty degrees F is substituted for the minimum temperature when it falls below 50° F and 86° F is substituted for the maximum if the temperature goes above 86° F.