Fungal disease management in U.S. corn production has undergone a major shift in the last 2 decades. The decision to apply fungicide, a management practice that was once rarely considered, is now contemplated annually by many U.S. corn producers. We investigate potential factors underlying the fungicide treatment decision. We use economics, agronomy, and plant pathology literature to develop a conceptual model of the fungicide treatment decision and test the model using a survey of Midwest corn producers. We find the treatment decision is positively related to perceived economic gains, but heuristic factors also have a strong influence.