Improving our Ability to Detect, Monitor, and Manage Corn Tar Spot in the Great Plains

Project Director: Tamra Jackson-Ziems, University of Nebraska-Lincoln

Funded in 2023

Tar spot disease of corn has caused yield losses of up to 50% in severe cases in some Midwest fields since its first confirmation in the United States in 2015 in Indiana and Illinois. Movement of the fungus causing tar spot, Phyllachora maydis, to the Great Plains states of Kansas, Nebraska, and South Dakota in 2021to 2022 has led to development of tar spot in new areas of the country where corn production practices and environments vary greatly. It is unclear how tar spot will respond in these new areas, especially where overhead pivot irrigation is often common and expected to exacerbate disease severity based on observations in other states. These uncertainties create greater risk for producers in the Great Plains.

In addition, on the forefront of the movement of the tar spot pathogen into the Great Plains, there’s need for additional diagnostic resources. Many field practitioners already struggle with disease diagnoses and especially differentiating similar symptoms of diseases. Diagnostic mistakes and delays can lead to ineffective management decisions and unnecessary expenses for producers. This project proposes outreach activities to demonstrate and train users in the region on the use of new, affordable microscope tools that are now widely available to enhance their diagnostic capabilities of tar spot and other common diseases.

Additionally, fields will be selected across the three participating Great Plains states of Kansas, Nebraska, and South Dakota, which have had confirmed issues with tar spot. The disease severity will be documented frequently through the growing season on plants in adjacent irrigated and non-irrigated areas under varying irrigation regimes. Disease progression will be compared to better understand the impacts of the diverse growing conditions and irrigation on tar spot development. Finally, tar spot samples from the Great Plains states will be compared phylogenetically to assess for fitness differences in those found in the region versus those found in other parts of the country.


  • Offer hands-on, interactive training workshops with affordable, contemporary microscopic tools focused on corn tar spot disease diagnostics
  • Evaluate tar spot development under different irrigated crop production environments in the Great Plains
  • Evaluate genetic and morphological diversity of Phyllachora maydis causing tar spot in the Great Plains.