Three Corn Diseases to Watch for in 2023

As the 2023 season gets started, we are taking a closer look at three important fungal diseases that are found over broad geographic areas and have the potential to impact corn. Knowing about these diseases now will help you scout and plan management strategies during the growing season.

1. Tar spot

Tar spot has been in the U.S. for nearly a decade and has become an annual concern in many Midwestern states and provinces like Illinois, Indiana, Iowa, Michigan, Wisconsin, and Ontario, Canada. While tar spot was not as yield-limiting in these areas in 2022, it has expanded its range, and has now been reported across the corn belt, as far west as Kansas, Nebraska, South Dakota, and as far east as New York, Maryland, and Pennsylvania. Southern states like Kentucky, Georgia and Florida have also confirmed this disease. This expanding range poses many questions on how environment influences disease development and where tar spot yield losses will be most severe this upcoming season. To prepare for 2023, learn how to identify tar spot, study research-based management options, and note that management recommendations may be specific to your state/province. This is an excellent time to contact your state Extension specialist and get their thoughts on how the disease should be managed in your area. In general, a fungicide application at VT/R1 will be sufficient if tar spot is a threat, but state-by-state recommendations may differ. If tar spot is on your farm, the CPN tar spot webbook, the corn ipmpipe map, and Tarspotter App are tools that can assist in answering questions and help monitor risk in-season.

2. Curvularia leaf spot

This disease is another new issue in the U.S., first reported in Louisiana in 2017. Curvularia leaf spot is confirmed in states across the southern U.S. and is potentially in Midwestern states. This leaf spot is a challenge to identify in the field in states where eyespot is also present, because the two diseases have almost identical symptoms. Laboratory diagnosis is likely needed in states where eyespot has been reported. Widespread yield loss has not been reported from Curvularia leaf spot, but its increasing prevalence in northern areas of the Mid-South and Midwest make it a potential concern worth watching. Hybrids vary in susceptibility to this disease, and yield losses may occur in susceptible hybrids, although more research is needed. Currently, fungicide efficacy for CLS is not yet well-defined.

3. Crown rot

Crown rot has received a lot of attention over the last few years. Increasing reports of it across the Midwest, Mid-south and eastern corn belt have prompted increased research on this under-studied disease. To prepare for 2023, check out the recent publication, “Frequently asked questions on crown rot” and learn what is currently known (and unknown) about this disease. Scouting fields at the late dough-early dent (R4-R5) growth stages can help identify potential crown rot issues before harvest. Look for “ghost” plants or plants that have prematurely senesced and split the lower crown of the plant to see if the crown is discolored. Effective management options are not yet known, but identifying fields with a history of the disease will be helpful once research determines what management practices are needed.

There are many other corn diseases that are annually important and may require management. Ultimately the diseases that could potentially impact your corn in 2023 will depend on local environmental conditions at critical points in the growing season. Check out all of the corn disease resources available on the Crop Protection Network and be ready for whatever 2023 brings!

Acknowledgments

Authors

Kiersten Wise, University of Kentucky; Mandy Bish, University of Missouri; Daren Mueller, Iowa State University; Rodrigo Onofre, Kansas State University; Trey Price, Louisiana State University, LSU AgCenter; Darcy Telenko, Purdue University; and Albert Tenuta, Ontario Ministry of Food, Agriculture and Rural Affairs.

Reviewers

 Travis Faske, University of Arkansas; and Andrew Friskop, North Dakota State University.

Photo Credits

All photos were provided by and are the property of the authors and contributors

This publication was developed by the Crop Protection Network, a multi-state and international collaboration of university/provincial extension specialists and public/private professionals that provides unbiased, research-based information to farmers and agricultural personnel.

Sponsors

This resource was supported by the National Corn Growers Association (NCGA).