The prevalence of four diseases of corn, Goss’s wilt and leaf blight, gray leaf spot, northern leaf blight and Diplodia ear rot, have increased greatly over the past few growing seasons.  Who is to blame?  The disease triangle is a standard concept in plant pathology that describes how disease is the result of an interaction between a host, a pathogen and the environment.  Could one or more of these factors have played a role in the increased disease we have seen in corn? Certainly, hybrid genetics may change as breeders strive for certain agronomic properties in the crop, such as yield potential.  Pathogens may evolve over time due to host and/or environmental selection pressures and become more aggressive.  Changes in agronomic practices, and/or climate may increase risk of infection and disease development.  A thorough knowledge of a  disease triangle can help identify risk factors that result in increased disease prevalence and severity.  Consequently, targeted management practices that reduce risk may be used decrease disease and protect yield potential.   This interactive presentation will review the disease triangle of each of the aforementioned pathosystems and discuss management practices that can be used to reduce their occurrence.