Research Brief

Breakthrough on tar spot pathogen enables field research

Close-up image of  corn tar spot.
Image of corn tar spot. Credit: José E. Solórzano

University of Minnesota researchers developed and reported processes for the first time to infect corn plants in the field with the corn tar spot pathogen, a relatively new disease threatening corn production across the United States. 

The new and novel process makes it possible for scientists to conduct research in the field — a critical step in better understanding the disease that first emerged in Minnesota in 2019.  

Recently published in Plant Disease, the research was funded by the University’s Minnesota Invasive Terrestrial Plants and Pests Center, supported by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). 

“Tar spot is a challenging pathosystem, and corn tar spot season has begun this year with the first reports coming from Kansas, Iowa, and Missouri,” said lead author José E. Solórzano, a graduate student at the University of Minnesota. “We have figured out how to induce the disease in controlled and field environments, which enhances our research and understanding of the disease, and we expect it will help other researchers as well.”

The study describes how to collect, store, prepare and apply inoculum to corn foliage to induce infection in the field. The study also provides novel insights into tar spot’s incubation, latent and infectious periods.

The researchers found: 

  • A single inoculation event can initiate tar spot and subsequent spread of the disease.
  • Inoculum stored at -20 degrees Celsius for 10 months can remain viable and lead to infection.
  • Tar spot can develop and spread in drier and less humid environmental conditions that were not previously considered conducive for this disease.

“Corn tar spot is a new and emerging disease that is poorly understood. This work advances the capacity to conduct research leading to improved understanding and management of this disease,” said co-author Dean Malvick, a professor in the College of Food, Agricultural and Natural Resource Sciences. 

The researchers will continue to study the biology of the tar spot-causing pathogen and the pathogen's host range to develop improved management strategies.

About the College of Food, Agricultural, and Natural Resource Sciences 
The University of Minnesota’s College of Food, Agricultural, and Natural Resource Sciences (CFANS) strives to inspire minds, nourish people, and sustainably enhance the natural environment. CFANS has a legacy of innovation, bringing discoveries to life through science and educating the next generation of leaders. Every day, students, faculty, and researchers use science to address the grand challenges of the world today and in the future. CFANS offers an unparalleled expanse of experiential learning opportunities for students and the community, with 12 academic departments, 10 research and outreach centers across the state, the Minnesota Landscape Arboretum, the Bell Museum of Natural History, and dozens of interdisciplinary centers. Learn more at

About the Minnesota Invasive Terrestrial Plants and Pests Center
The Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC) was founded by the Minnesota Legislature to research the prevention, detection and control of terrestrial invasive species. MITPPC researchers use transformative science to prevent and minimize the threats posed by land-based invasive plants, pathogens, and pests. Founded in 2015, MITPPC is the only research center of its kind in the country, and the center's work to protect the state's native prairies, forests, wetlands, and agricultural resources benefits all of Minnesota and beyond. Learn more at

Media Contacts

Lori Fligge

College of Food, Agricultural and Natural Resource Sciences, Twin Cities