Corn Disease Loss Estimates From the United States and Ontario, Canada — 2022

Corn diseases annually reduce yield in the United States and Canada. Diseases of importance vary from year to year, and diseases that affect yield are based on many factors, including weather conditions, crop production practices, and hybrid susceptibility to disease.

Plant pathologists representing 28 corn-producing U.S. states and Ontario, Canada, estimated the percent yield loss from corn disease for each participating state or province. These reports account for 14.0 billion bushels (99.0 percent) of the total corn produced in the United States and Ontario in 2022 (Figure 1). The yield loss estimates include root rots, seedling blights, foliar diseases, crazy top, smuts, stalk rots, ear rots, and nematodes.

This publication documents the impact of major diseases on corn production during 2022. The Corn Disease Working Group (CDWG) revises disease loss estimates annually. It is important to note that methods for estimat­ing disease loss vary by state or province. The estimates may be based on statewide disease surveys; feedback from university extension, industry, and farmer represen­tatives; and personal experience with disease losses.

The CDWG determined disease loss values based on yield before estimated losses for each state or province using this formula:

(harvested bushels/[{100 – percent estimated disease loss}/100])

The CDWG then formulated total bushels lost per disease ([percent loss/100] x yield before estimated loss) for each state or province. This does not include mycotoxin contamination as this reduces quality rather than quantity of grain.

2022 Conditions and Production

The United States produced 13.7 billion bushels of corn in 2022, and Ontario, Canada produced 0.4 billion bushels. The 2022 cropping season was hot and dry across most of the corn-producing states. Above average temperatures were observed during pollination and grain fill in 2022 throughout much of the contiguous U.S. Multiple corn producing states experienced drought, reducing the risk from many foliar disease-causing pathogens in those locations. Concerns about ear rots and harmful mycotoxins linked with drought conditions, such as Aspergillus ear rot and aflatoxin, were high, although widespread mycotoxin issues were not observed.

2022 Disease Losses

In 2022, disease reduced corn bushels by 2.8 percent across the U. S. And by 2.7 percent in Ontario. This is down from the overall values from each of the previous five years, which were 6.5, 3.9, 6.8, 10.9, and 6.7 percent for 2021, 2020, 2019, 2018, and 2017, respectively. Tar spot reduced yield more than the next greatest yield-reducing disease by a wide margin. After tar spot, Fusarium stalk rot, nematodes that feed on corn, crown rot, and bacterial leaf streak, caused the most estimated yield loss in descending order. Table 1 provides yield loss estimates for all diseases. Categories for Curvularia leaf spot and crown rot were added in 2022; however, detailed notes allowing for the separation of crown rot and stalk rot were not obtained in all states.

Table 1. Estimated corn yield losses (millions of bushels) due to diseases in 28 U.S. corn-producing states and Ontario, Canada in the 2022 growing season.

Diseases in the Northern United States

Tar spot was the most damaging disease in the northern U. S. in 2022 — with 116.8 million bushels lost. Fusarium stalk rot caused the second greatest loss followed by nematodes that feed on corn, crown rot, and bacterial leaf streak (see Table 2). Tar spot and Fusarium stalk rot in 2022 caused approximately half of the yield loss experienced by the same diseases in 2021.

Table 2. Estimated corn yield losses due to the five most significant diseases in the northernmost U.S. states¹ in 2022.

¹ U.S. States include Colorado, Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Nebras­ka, New York, North Dakota, Ohio, Pennsylvania, South Dakota, and Wisconsin.

Diseases in Southern States

Overall, losses due to corn diseases in southern states were very low in 2022. Plant-parasitic nematodes caused the greatest estimated yield loss in the southern United States in 2022, followed by the foliar diseases gray leaf spot and southern rust (see Table 3). The top three yield-reducing diseases were the same as in 2021.

Table 3. Estimated corn yield losses due to the five most significant diseases in the southernmost U.S. states¹ in 2022.

¹ Alabama, Arkansas, Delaware, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, South Carolina, Tennessee, Texas, and Virginia.

Diseases in Ontario, Canada

Foliar diseases and stalk rots were the greatest cause of yield loss in Ontario. The top yield-reducing diseases were northern corn leaf blight, tar spot, and Gibberella stalk rot (see Table 4).

Table 4. Estimated corn yield losses due to the most significant diseases in Ontario, Canada in 2022.

Mycotoxin Losses

Plant pathologists estimated that only 0.13 percent and 0.05 percent of the harvested grain in the U. S. And Ontario, Canada, respectfully, was contaminated with mycotoxins in 2022. Similarly low levels were also observed in 2021 and 2020. Mycotoxin losses are calculated using the USDA-NASS reported production, rather than what production would be without other diseases.

Summary

Total yield reduction caused by disease in 2022 was less than that observed in any other year since data collection began in 2012; however, individual states experienced significant disease losses where conditions were favorable. Environmental conditions were dry during the growing season in parts of the U. S. in 2022, which affected the presence of and damage from many diseases. Tar spot continues to expand geographically while the majority of yield reduction from this disease in 2022 occurred in Illinois and Iowa. Tar spot was found in several states where it has not been observed previously including Kansas, Maryland, South Dakota, and Virginia. Corn nematodes caused the greatest yield reductions in Kansas and Nebraska compared to other states.

Disclaimer

The disease loss estimates in this publication were provided by members of the Corn Disease Working Group (CDWG). This information is only a guide. The values in this publication are not intended to be exact estimates of corn yield losses due to diseases. The members of the CDWG used the most appropriate means available to estimate disease losses and assume no liability resulting from the use of these estimates. 

Values reported in this document were accurate as of publication date and do not reflect corrections or updates occurring since that time. For the most up-to-date values and additional information on yield and economic losses due to diseases, see the Field Crop Disease Loss Calculator. This document was updated on March 16, 2023 due to the need to revise values of crown rot and Curvularia leaf spot, which were originally calculated incorrectly.

Acknowledgements

Authors

Daren Mueller, Iowa State University; Kiersten Wise, University of Kentucky; and Adam Sisson, Iowa State University

Contributors

Ed Sikora, Auburn University; Travis Faske, University of Arkansas; Ron Meyer, Colorado State University; Alyssa Koehler, University of Delaware; Bob Kemerait, University of Georgia; Chelsea Harbach, University of Illinois; Darcy Telenko, Purdue University; Alison Robertson, Iowa State University; Rodrigo Onofre, Kansas State University; Trey Price, Louisiana State University; Marty Chilvers, Michigan State University; Dean Malvick, University of Minnesota; Tom Allen, Mississippi State University; Mandy Bish, University of Missouri; Tamra Jackson-Ziems and Kyle Broderick, University of Nebraska-Lincoln; Gary Bergstrom, Cornell University; Ron Heiniger, North Carolina State University; Andrew Friskop, North Dakota State University; Pierce Paul, Ohio State University; Albert Tenuta, Ontario Ministry of Agriculture, Food and Rural Affairs; Greg Roth, Alyssa Collins, and Paul Esker, Penn State University; John Mueller and Michael Plumblee, Clemson University; Madalyn Shires, South Dakota State University; Heather Kelly, University of Tennessee; Tom Isakeit, Texas A&M University; David Langston and Yuan Zeng, University of Virginia; and Damon Smith, University of Wisconsin-Madison. 

Reviewers

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

Production data from the United States Department of Agriculture-National Agriculture Statistics Service and the Statistics Canada. Climate information from the National Oceanic and Atmospheric Administration-National Center for Environmental Information.

United States Department of Agriculture National Agricultural Statistics Service. Quick Stats Database. Accessed 25 January 2023.

Statistics Canada. Table 32-10-0359-01 Estimated areas, yield, production, average farm price and total farm value of principal field crops, in metric and imperial units. Accessed 26 January 2023.

Sponsors

In addition to support from United States Department of Agriculture - National Institute of Food and Agriculture, this project was funded in part through the National Corn Growers Association and the Grain Farmers of Ontario through the Canadian Agricultural Partnership (CAP), a federal-provincial territorial initiative.