Corn Disease Loss Estimates - 2019

Corn Disease Loss Estimates From the United States and Ontario, Canada — 2019

CPN-2007-19. DOI:

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 selection and susceptibility to disease. 

Plant pathologists representing 26 corn-producing U.S. states and Ontario, Canada, estimated the percent yield loss from corn disease in their states. These reports account for 13.8 billion bushels (98.1 percent) of the total corn produced in the United States and Ontario in 2019. The yield loss estimates include root rots, seedling blights, foliar diseases, crazy top, smuts, stalk rots, and ear rots

This publication documents the impact of major diseases on corn production during 2019. 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: bushels harvested/[(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.

Additional information on yield and economic losses due to corn can be found at the CPN Field Crop Disease Loss Calculator

2019 Conditions and Production

The United States and Ontario produced more than 14 billion bushels of corn in 2019. Much of the United States experienced conditions that prevented timely planting of corn and wet conditions during fall contributing to harvest difficulties.

2019 Disease Losses 

In all, 6.8 percent of the total estimated corn bushels were lost in 2019 due to disease in the 26 corn-produc­ing states and Ontario. This is down from the 10.9 percent losses experienced in 2018, and similar to the 6.7 percent loss experienced in 2017. Table 1 provides yield loss estimates for all diseases.

Table 1. Estimated corn yield losses (millions of bushels) due to diseases in 26 U.S. corn-producing states and Ontario, Canada in the 2019 growing season.


2019 Estimated Yield Loss (millions of bushels)

Root Rots and Seedling Blights



Root rots


Seedling blights


Leaf and Aboveground Diseases

Gray leaf spot


Northern corn leaf blight


Tar spot


Southern rust


Physoderma leaf spot


Bacterial leaf streak


Carbonum leaf spot


Goss's wilt


Common rust




Anthracnose leaf blight


Common smut


Southern leaf blight


Holcus spot


Head smut


Other leaf and aboveground diseases


Stewart's disease


Crazy top


Virus -- Maize Dwarf Mosaic 


Other virus and virus-like diseases


Stalk Rots

Fusarium stalk rot


Anthracnose stalk rot and top dieback


Gibberella stalk rot


Diplodia stalk rot


Others stalk rot


Charcoal rot


Bacterial stalk rot


Ear Rots

Fusarium ear rot


Gibberella ear rot


Others ear rot


Diplodia ear rot


Aspergillus ear rot



Loss from mycotoxin contamination 

6.4% of harvested grain contaminated

Figure 2. Nematodes caused an estimated 65.5 million bushels of corn yield loss in 2019.  

Figure 3. Gibberella ear rot was estimated to have reduced yields by nearly 60 million bushels in 2019, second only to Fusarium ear rot.

Diseases in the Northern United States and Ontario

Fusarium stalk rot was the most damaging disease in the northern United States and Ontario in 2019 — more than 146 million bushels lost. Gray leaf spot caused the second greatest loss while Fusarium ear rot caused the next greatest yield loss (see Table 2). 

Overall, stalk rots and ear rots contributed to the greatest yield reductions in 2019, while foliar diseases were the primary issue in 2018. 

Table 2. Estimated corn yield losses due to diseases in the 12 northernmost U.S states and Ontario, Canada in 2019¹


2019 Estimated Yield Loss (millions of bushels)

Fusarium stalk rot


Gray leaf spot


Fusarium ear rot


Northern corn leaf blight


Gibberella ear rot


Anthracnose stalk rot and top dieback


Tar spot


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


Diseases in Southern States 

Nematodes caused the greatest damage in the southern United States in 2019 and Fusarium stalk rot was second, breaking a trend beginning in 2015. Gray leaf spot, bacterial leaf streak, and southern rust were the primary foliar diseases present (Table 3). 

Table 3. Estimated corn yield losses due to diseases to in the 14 southernmost states in 2019¹


2019 Estimated Yield Loss (millions of bushels)



Fusarium stalk rot


Gray leaf spot


Fusarium ear rot


Bacterial leaf streak


Southern rust


Root rots


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


Mycotoxin Losses

In 2019, ear rots were not as common in the Midwest as in 2018. Plant pathologists estimated that 6.4 percent of the harvested grain in the United States and Ontario was contaminated in 2019.

Figure 1. Gray leaf spot is a common foliar disease of corn. It was estimated to have reduced yields by more than 146.3 million bushels in 2019 — more than double that of any other foliar disease that season.


Environmental conditions varied across the United States and Ontario in 2019, which affected the presence of and damage from many diseases. Overall, estimated yield losses from corn disease were much less in 2019 than 2018.


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. 

Find out More

The Crop Protection Network (CPN) is a multi-state and international collaboration of university and provincial extension specialists, and public and private professionals who provide unbiased, research-based information to farmers and agricultural personnel. Our goal is to communicate relevant information that will help professionals identify and manage field crop diseases. 

Find more crop disease resources at

Additional information on yield and economic losses due to corn can be found at the CPN Field Crop Disease Loss Calculator



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


Members of the Corn Disease Working Group are university scientists from many institutions, including: Auburn University, University of Arkansas, Colorado State University, Cornell University, University of Delaware, University of Guelph, University of Illinois, Iowa State University, Kansas State University, University of Kentucky, Louisiana State University, Michigan State University, University of Minnesota, Mississippi State University, University of Missouri, University of Nebraska, North Carolina State University, North Dakota State University, Ohio State University, Penn State University, Purdue University, South Dakota State University, University of Tennessee, Texas A&M University, University of Virginia, and University of Wisconsin-Madison.

The following individuals contributed to this publication: 

Austin Hagan and Ed Sikora, Alabama; Travis Faske, Arkansas; Ron Meyer, Colorado; Alyssa Koehler, Delaware; Nathan Kleczewski, Illinois; Darcy Telenko, Indiana; Alison Robertson, Iowa; Doug Jardine, Kansas; Carl Bradley, Kentucky; Trey Price, Louisiana; Alyssa Koehler, Maryland; Marty Chilvers, Michigan; Dean Malvick, Minnesota; Tom Allen, Mississippi; Kaitlyn Bissonnette, Missouri; Tamra Jackson-Ziems, Nebraska; Gary Bergstrom, New York; Ron Heiniger and Lindsey Thiessen, North Carolina; Andrew Friskop, North Dakota; Pierce Paul, Ohio; Albert Tenuta, Ontario; Greg RothAlyssa Collins, and Paul Esker, Pennsylvania; Emmanuel Byamukama, South Dakota; Heather Kelly, Tennessee; Tom Isakeit, Texas; Hillary Mehl, Virginia; and Damon Smith, Wisconsin. 

Photos by Adam Sisson and Gary Munkvold, Iowa State University; and Tom Hillyer.

In addition to support from United States Department of Agriculture - National Institute of Food and Agriculture, this project was funded in part through Growing Forward 2 (GF2), a federal-provincial territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario. 

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.

This information in this publication is only a guide, and the authors assume no liability for practices implemented based on this information. Reference to products in this publication is not intended to be an endorsement to the exclusion of others that may be similar. Individuals using such products assume responsibility for their use in accordance with current directions of the manufacturer.

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Corn Disease Loss Estimates - 2019

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