Growers across the country are reporting unprecedented incidences of tar spot this harvest season. When conditions are favorable for the disease, it can cause significant yield loss in susceptible corn hybrids. Tar spot was first detected in the U.S. in 2015 in northern Illinois and Indiana, and it has quickly spread through the Corn Belt. The disease causes significant losses for farmers’ livelihoods. Efforts to combat tar spot have been hindered by the difficulty of growing Phyllachora maydis—the fungus responsible for the disease—in a laboratory setting which, in turn, limits researchers’ capabilities to study and understand it.
The National Corn Growers Association has two Action Teams, both armed with support from state checkoff dollars, focused on aiding the fight against tar spot.
In 2019, the Sustainable Ag Research Action Team (SARAT)—along with Corteva Agriscience, Wyffels Hybrids, Illinois Corn Growers Association and Purdue University—helped to provide matching research funding towards the Foundation for Food & Agricultural Research’s (FFAR) Rapid Outcomes for Agricultural Research (ROAR) grant, which was awarded to a group of researchers for the study of tar spot on corn. The research team was comprised of plant pathologists from the University of Illinois, Iowa State University, Purdue University, Michigan State University, The Ohio State University and the University of Wisconsin-Madison.
In the findings of their peer-reviewed article, Documenting the Establishment, Spread, and Severity of Phyllachora maydis on Corn, in the United States (Journal of Integrated Pest Management, Volume 11, Issue 1, 2020), the ROAR research group concluded that “coordinated efforts to monitor continued spread will be essential in ensuring that farmers and the agronomic community are educated in areas of greatest risk and in disease identification and disease management and mitigation techniques.”
Growers can monitor 2021’s reported incidences of tar spot spread through Corn impPIPE mapping. If they see tar spot issues in their own fields, growers are strongly encouraged to help document those occurrences through Corn impPIPE’s reporting form.
In addition to monitoring and documenting the disease this harvest season, best management practices can be employed to mitigate the spread of tar spot for next year. The Production Technology Access Action Team (PTAAT) has funded support for the Crop Protection Network (CPN) for the last two years. That network is a product of Land Grant Universities, and it provides unbiased crop protection information to farmers, educators and ag personnel. CPN’s Corn Disease Management: Tar Spot publication recommends that growers:
- Manage residue of the affected crop to reduce inoculum from overwintering,
- Rotate to other crops to reduce the primary tar spot inoculum,
- Avoid highly susceptible hybrids, and
- Investigate effective fungicides.
These proactive strategies can help farmers get ahead of tar spot for the 2022 harvest season. NCGA will continue to promote further progress in the study and mitigation of tar spot in order to identify practices and tools for farmers that reduce the impact of this emerging disease.
To read an overview about work being conducted to find a genetic resistance to breeding - Michigan State University’s Great Lakes Tar Spot Initiative: Mobilizing Resistance in Maize