Goss’s wilt and leaf blight (GWLB) (Clavibacter nebraskensis) is a yield-limiting disease of corn (Zea mays L.). Research conducted in other corn growing states have indicated yield losses as severe as 60% on susceptible hybrids. In 2011, the disease was first reported in southcentral North Dakota (ND). Concurrently, corn production was increasing in ND due to favorable grain prices. With increased production, there was concern about disease prevalence and the impact of GWLB on corn yields in the state. In order to determine which corn diseases are present in ND, and to gain a better understanding of the C. nebraskensis population in ND and its impact on corn yield, three studies were conducted. Prior to 2014, no formal corn foliar disease survey had been documented in ND, thus the first objective was to document the prevalence of foliar diseases of corn in ND. Results indicate that four diseases are common in ND; common rust, common smut, northern corn leaf blight, and GWLB. One corn disease is of economic concern in ND; GWLB. The objectives of the second study were to evaluate phenotypic and genotypic differences among isolates of the ND C. nebraskensis population. Results indicate significant differences in the amount of disease caused and the rate of disease progression by the isolates. Genetic differences among isolates also exist, but both phenotypic and genotypic differences appear to be random with no association to isolate origin. The objective of the third study was to evaluate yield loss due to GWLB based on infection timing and hybrid resistance. Results indicated that infection by C. nebraskensis at vegetative growth stages caused yield loss in excess of 40% on the susceptible hybrid, while infection at silking resulted in losses around 2%. Regardless of infection timing, yield loss on the resistant hybrid did not exceed 11%. The impacts of these studies will be to direct research efforts to economically important diseases (GWLB) and to strengthen GWLB management recommendations for ND corn growers.