In this week’s CropCast, Seth Naeve and David Nicolai welcomed Dr. Dean Malvick, University of Minnesota Extension plant pathologist for corn and soybeans. Dean discussed the selection and Corn Tar Spot management criteria for growers to consider when choosing their 2025 corn seed inputs and crop inputs. While crop yield data from multiple sites in 2024 is extremely important, yield stability over time as affected by disease resistance for corn tar spot is essential in the selection process. 

Dr. Malvick provided a review of the corn tar spot disease biology and the 2024 spread of the disease in corn production fields this year across Minnesota and into adjoining states. Dean specifically provided what is known and what is not known about progression and incidence of the disease occurrence in relation to weather, environment, wind spread and crop rotation effects. Because of the many disease risk factors that can occur each year there is not a simple answer to managing this disease. Dean discussed these factors and possible management controls such as hybrid corn selection, along with the use and timing of foliar fungicides. He also reviewed the best management practice for timely scouting for the presence of the disease in the summer of the growing season to provide more information when determining the use of corn foliar fungicides.

To see a distribution map where tar spot has been confirmed and real-time disease activity during the growing season in the US, visit https://corn.ipmpipe.org/tarspot/.

To learn more about the identification, biology, weather and research trials relating to the management of corn tar spot please refer to a previous episode of a University of Minnesota Strategic Farming webcast report from 2023.