Corn Disease Loss Estimates from the United States and Ontario, Canada — 2023

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 environmental conditions, crop production practices, and hybrid susceptibility to disease. 

Plant pathologists representing 29 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 approximately 15.6 billion bushels (99.2 percent) of the total corn produced in the United States and Ontario in 2023 (Figure 1). The yield loss estimates include root rots, seedling blights, foliar diseases, crazy top, smuts, stalk rots, ear rots, and nematodes. 

This publication summarizes the estimated impact of major diseases on corn production during 2023. 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 specialized experience with disease losses. 

The CDWG determined disease loss values based on yield before estimated losses for each state or province using the 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, which reduces quality rather than quantity of grain. 

2023 Conditions and Production 

The United States produced 15.3 billion bushels of corn in 2023, and Ontario, Canada, produced 0.4 billion bushels. Data from Oklahoma was added for the first time this year. In general, the 2023 cropping season was hot and dry in many corn-producing states. Above average temperatures were observed during pollination and grain fill throughout much of the contiguous U.S. Multiple corn producing states experienced drought, reducing the risk of yield losses 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 aflatoxin issues were not observed. Other ear rots and mycotoxins, such as Gibberella ear rot and deoxynivalenol, and Fusarium ear rot and fumonisins, were problematic in certain areas of the United States.

2023 Disease Losses 

In 2023, disease reduced corn yield by an estimated 2.9 percent across the U. S. and by 3.9 percent in Ontario, resulting in a total estimated loss of 465.1 million bushels. Overall reported percent losses were similar to losses reported for 2022, but much reduced from the average loss of 9.0 percent observed between 2012 and 2021. Interestingly, nematodes that parasitize corn caused the greatest yield losses compared to any other disease or disease group; this is the only time nematodes have ranked first nationally since data collection began in 2012. Reported losses caused by nematodes in 2023 are not much greater than those from 2022. However, there was a reduction in foliar or stalk rot diseases that more commonly cause the greatest losses, such as tar spot or Fusarium stalk rot. Table 1 provides yield loss estimates for all diseases, and Figure 3 shows proportionate losses for the top-ranking diseases. As in 2022, 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 29 U.S. corn-producing states and Ontario, Canada, in the 2023 growing season.

¹ Includes lance, lesion, root-knot, sting, stubby root, and additional nematode genera; ² Detailed notes allowing for the separation of crown rot and other stalk rots were not obtained in all states; ³ Includes Trichoderma ear rot in Louisiana, New York, and Ohio. 

Diseases in the Northern United States 

Nematodes that parasitize corn caused the greatest estimated yield reduction in the northern U.S. in 2023 — with 51.0 million bushels lost. Stalk and ear rots composed the other top yield reducers and included Fusarium stalk rot, Gibberella ear rot, anthracnose stalk rot and top dieback, and Fusarium ear rot in descending order (see Table 2). Notably, tar spot was absent from the top five yield-reducing diseases in this region in 2023. 

Table 2. Estimated corn yield losses due to the five most significant diseases in the northernmost U.S. states¹ in 2023.

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 the Southern States 

Overall, losses due to corn diseases in southern states were low in 2023. As in 2022, nematodes that parasitize corn caused the greatest estimated yield loss in the southern United States. Since data collection began in 2012, nematodes that parasitize corn have always been one of the top three yield-reducing diseases each year. Gray leaf spot and Fusarium, Diplodia, and Gibberella ear rots followed in descending order in 2023 (see Table 3). 

Table 3. Estimated corn yield losses due to the five most significant diseases in the southernmost U.S. states¹ in 2023.

¹ U.S. States include Alabama, Arkansas, Delaware, Georgia, Kentucky, Louisiana, Maryland, Mississippi, Missouri, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia. 

Diseases in Ontario, Canada

The top yield-reducing diseases in Ontario, Canada, in 2023 were tar spot, northern corn leaf blight, nematodes that parasitize corn, Gibberella ear rot, and gray leaf spot (see Table 4). 

Table 4. Estimated corn yield losses due to the most significant diseases in Ontario, Canada, in 2023.

Mycotoxin Losses 

Plant pathologists estimated that only 0.4 percent and 0.0 percent of the harvested grain in the U.S. and Ontario, Canada, respectively, was contaminated with mycotoxins in 2023. Similarly, low levels were also observed in the previous three year period. Mycotoxin losses are calculated using the USDA-NASS reported production rather than what production would be without other diseases. 

Summary 

The total estimated yield reduction caused by disease in 2023 was less than that observed in any other year since data collection began in 2012, except for 2022. Environmental conditions were dry during the growing season in parts of the U.S. in 2023, which affected the occurrence  of and damage from many diseases. This was the first time nematodes that parasitize corn ranked as the top yield-reducing disease, driven primarily by losses reported in Nebraska and Kansas. As in previous years, tar spot continued to expand to new locations along the margins of the existing distribution but did not cause significant yield loss in these areas. 

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 the 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.

Acknowledgements

Data Compilation

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

Authors

Ed Sikora, Auburn University; Travis Faske, University of Arkansas; Ron Meyer, Colorado State University; Alyssa Koehler, University of Delaware; Bob Kemerait, University of Georgia; Santiago Mideros, University of Illinois; Darcy Telenko, Purdue University; Alison Robertson, Daren Mueller, and Adam Sisson, Iowa State University; Rodrigo Onofre, Kansas State University; Kiersten Wise, University of Kentucky; 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; Gary Bergstrom, Cornell University; Ron Heiniger and Daisy Ahumada, North Carolina State University; Andrew Friskop, North Dakota State University; Pierce Paul, Ohio State University; Maira Rodrigues Duffeck, Oklahoma 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 and Nolan Anderson, Texas A&M University; David Langston and Yuan Zeng, University of Virginia; and Damon Smith, University of Wisconsin-Madison. 

Reviewers

Dylan Mangel, University of Nebraska-Lincoln; Richard W. Webster, 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 14 February 2024.

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 14 February 2024.

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 Sustainable Canadian Agricultural Partnership (Sustainable CAP), a federal-provincial territorial initiative.