Corn Disease Loss Estimates For the United States and Ontario, Canada — 2016

Corn Disease Loss Estimates For the United States and Ontario, Canada — 2016

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 24 corn-producing U.S. states and Ontario, Canada, estimated the percent yield loss from corn disease in their states. These reports account for 15.1 billion bushels (97.7 percent) of the total corn produced in the United States and Ontario in 2016 (Figure 1). The yield loss estimates include root rots, seedling blights, foliar diseases, crazy top, ear and head smuts, stalk rots, and ear rots.

This article documents the impact of major diseases on corn production during 2016. 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 estimated disease 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.

2016 Conditions and Predictions

The United States and Ontario produced nearly 15.5 billion bushels of corn in 2016, and many areas reported record yields. Overall, temperatures were very warm across most of the Corn Belt, which contributed to an increase in diseases like gray leaf spot and southern rust.

2016 Disease Losses

In all, 10.8 percent of the total estimated corn bushels were lost in 2016 due to disease in 24 corn-producing states and Ontario, which is down from a 13.5 percent loss in 2015, but similar to what was experienced in 2014. Table 1 provides yield loss estimates for all diseases.

Diseases in the Northern United States and Ontario

Gray leaf spot was the most damaging disease in the northern United States and Ontario in 2016 — nearly 214 million bushels lost (Table 2). Anthracnose stalk rot was the second most damaging disease.

Warmer conditions through most of this area favored gray leaf spot development. Foliar diseases (such as southern rust and northern corn leaf blight) were also prevalent, but Goss’s wilt was less damaging than in previous years. A new bacterial disease (bacterial leaf streak) was identified in several states, but yield losses to this disease are unknown.

Diseases in Southern States

Fusarium stalk rot caused the greatest damage in the southern United States in 2016, while nematodes were second, which is similar to 2015. Southern rust, gray leaf spot, and Goss’s wilt were the primary foliar diseases present (Table 3).

Mycotoxin Losses

In 2016, 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 2016.


Environmental conditions varied across the United States and Ontario in 2016, which affected the presence of and damage from many diseases.

The foliar disease gray leaf spot was most prevalent across northern states and Ontario in 2016, likely due to the warmer weather. Stalk rots 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; Delaware – Nathan Kleczewski; Illinois – Angie Peltier; Indiana – Kiersten Wise; Iowa – Alison Robertson; Kansas – Doug Jardine; Kentucky – Carl Bradley; Louisiana – Clayton Hollier; Maryland – Nathan Kleczewski; Michigan – Marty Chilvers; Minnesota – Dean Malvick; Mississippi – Tom Allen; Missouri – Bill Wiebold; 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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