Foliar fungicides have traditionally not been used in commercial corn because they have seldom been profitable. However, the use of foliar fungicides in hybrid corn production has increased dramatically in the past four years, primarily because of higher grain prices and physiological, yield-enhancing effects that are claimed by the agrochemical industry but are not related to reduced disease. Of concern is the fact that the use of fungicides has shifted attention from the sound use of integrated pest management (IPM) tactics for disease management, even those these tactics are designed to ensure efficient use of fungicides and maximize net return.
Since 2007, I have been conducting fungicide field trials on corn in collaboration with colleagues at ISU, University of Illinois, University of Wisconsin and The Ohio State University. The goal of these trials has been to provide unbiased data that help corn and soybean farmers make economically justified decisions regarding fungicide use. We have shown that fungicide profitability increases with disease pressure. Common fungal diseases of corn in Iowa are gray leaf spot and northern leaf blight.