Corn Disease Loss Estimates For the United States and Ontario, Canada — 2015

Corn Disease Loss Estimates For the United States and Ontario, Canada — 2015

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 in each of 22 corn-producing U.S. states and Ontario, Canada estimated the percent yield loss from corn disease in their states. These reports account for 13.6 billion bushels (97.2 percent) of the total corn produced in the United States and Ontario in 2015 (Figure 1). Root rots, seedling blights, foliar diseases, crazy top, ear and head smuts, stalk rots, and ear rots are included in the yield loss estimates.

This article documents the impact of major diseases on corn production during 2015. 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:

[(100 – percent estimate loss) ÷ 100]/ bushels harvested


The CDWG then formulated total bushels lost per disease (percent loss x yield before estimated losses) for each state or province.

2015 Conditions and Production

The United States and Ontario produced more than 13.9 billion bushels of corn in 2015, and many areas reported record yields. Overall, temperatures were very mild across most of the Corn Belt, which contributed to an increase in diseases like northern corn leaf blight. The late summer and fall were hot and dry across much of the United States and Ontario, which facilitated a timely harvest, but led to an increase in stalk rot diseases compared to 2014.

 2015 Disease Losses

In all, 13.5 percent of the total estimated corn bushels were lost in 2015 due to disease in 22 corn-producing states and Ontario, which is up from a 10.8 percent loss in 2014. Table 1 provides yield loss estimates for all diseases.

Diseases in the Northern United States and Ontario

Northern corn leaf blight was the most damaging disease in the northern United States and Ontario in 2015 — nearly 550 million bushels lost. This is more than twice the number of bushels than the second most damaging disease, anthracnose stalk rot.

Mild conditions through most of this area favored northern corn leaf blight development. Foliar diseases (such as gray leaf spot) were also prevalent, but Goss’s wilt was less damaging than in previous years. Southern rust and stalk rots caused more yield loss in the Midwest than in past years.

Diseases in Southern States

Fusarium stalk rot caused the greatest damage in the southern United States in 2015. Nematodes were second. Gray leaf spot, southern rust, and northern corn leaf blight were the primary foliar diseases present (Table 3). Seedling blights and root rots were more damaging in this area in 2015 compared to previous years.

Mycotoxin Losses

In 2015, ear rots also caused minor losses through mycotoxin-contaminated corn grain. Plant pathologists estimated that 0.9 percent of the harvested grain in the United States and Ontario was contaminated in 2015.


Environmental conditions varied across the United States and Ontario in 2015, which affected the presence of and damage from many diseases.

The foliar disease northern corn leaf blight was most prevalent across northern states and Ontario in 2015, likely due to mild weather. Stalk rots and seedling blights continue to be important diseases across the United States and Ontario.


The disease loss estimates in this article 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.

Reference to products in this article 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.


Daren Mueller – Iowa State University; Kiersten Wise – Purdue University; Adam Sisson – Iowa State University


The following individuals contributed to this publication:

Arkansas – Travis Faske; Colorado – Bruce Bosley, Ron Meyer; Illinois – Carl Bradley; Indiana – Kiersten Wise; Iowa – Alison Robertson; Kansas – Doug Jardine; Kentucky – Paul Vincelli; Louisiana – Clayton Hollier; Minnesota – Dean Malvick; Michigan – Marty Chilvers; Mississippi – Tom Allen; Missouri – University of Missouri Extension; Nebraska – Tamra Jackson; New York – Gary Bergstrom; North Carolina – Steve Koennig; North Dakota – Andrew Friskop; Ohio – Pierce Paul; Ontario – Albert Tenuta; Pennsylvania – Greg Roth, Alyssa Collins; South Dakota – Connie Tande; Tennessee – Heather Kelly; Texas – Tom Isakeit; Wisconsin – Damon Smith

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