Wheat Disease Loss Estimates from the United States and Ontario, Canada — 2020

NOTE: This document was updated in July 2024 to reflect the removal of Karnal bunt, which was mistakenly recorded in a single state, and to correct the total bushels lost due to disease in the northern United States.  

Wheat 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 variety selection and susceptibility to disease.

Plant pathologists representing 29 wheat-producing U.S. states and Ontario, Canada, estimated the percent yield loss from wheat disease in their states or province. These reports account for nearly 1.7 billion bushels (87.4 percent) of the total wheat produced in the United States and Ontario in 2020 (Figure 1). The yield loss estimates include foliar, root, stem, head, and kernel diseases in the states represented in this survey.

This publication documents the impact of major diseases on wheat production during 2020. The North Central Regional Committee on Management of Small Grain Diseases (NCERA 184) and the Western Wheat Workers (WERA 97) 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.

Disease loss values are based on yield before estimated losses for each state or province using this formula:

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

Total bushels lost per disease are then formulated using ([percent loss/100] x yield before estimated loss) for each state or province.

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

2020 Conditions and Production

Farmers in the United States and Ontario planted wheat on 45.6 million acres in 2020. This produced 1.9 billion bushels of wheat, worth nearly $9.9 billion USD. Much of the western U.S. and northern Plains experienced below average precipitation; above average levels of precipitation occurred across many eastern U.S. states. In general, the continental U.S. had above average temperatures. Many major weather or climate events occurred in 2020 in the U.S., including drought, hurricanes, and severe storms.

2020 Disease Losses

In 2020, disease reduced wheat bushels by 7.7 percent across the U.S. states included in this survey and by 2.3 percent in Ontario. Table 1 provides yield loss estimates for all diseases.

Table 1. Estimated wheat yield losses from diseases in 29 wheat producing states in the United States and Ontario, Canada in 2020.

¹Can include needle, root-gall, root-knot, stem, stubby-root, and stunt nematodes; ²Can include Alternaria leaf blight, anthracnose, Ascochyta leaf spot, bacterial mosaic, and downy mildew; ³Can include pink snow mold, speckled snow mold, and snow rot; ⁴Can include Agropyron mosaic and Brome mosaic; ⁵A portion of the estimated yield loss value for common bunt in the U.S. may be due to post harvest grain discounts reported from Kansas.

Diseases in the Northern United States

Bacterial leaf streak and black chaff was the most damaging disease in the northern United States in 2020 — 22.9 million bushels lost (see Table 2). Fusarium head blight caused the second greatest loss in 2020, causing approximately half the amount of yield loss compared to 2019. Overall, nearly 111 million bushels of wheat were estimated to have been lost due to diseases in the northern United States.

Table 2. Estimated wheat yield losses due to the five most significant diseases in the northernmost U.S. states¹ in 2020.

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

Diseases in Southern States

Leaf rust caused the greatest estimated wheat yield losses in the southernmost U.S. states in 2020 (Table 3). Although not even in the top five diseases in 2019, tan spot was the second greatest cause of yield loss in 2020. Overall, more than 21 million bushels of yield loss occurred in the southernmost United States due to disease.  

Table 3. Estimated wheat yield losses due to the five most significant diseases in the southernmost U.S. states¹ in 2020.

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

Diseases in Ontario, Canada

Stagonospora leaf and glume blotch, Septoria tritici blotch, and Fusarium root, crown, and foot rot caused the greatest estimated wheat yield loss in Ontario, Canada in 2020 (Table 4). Although these three diseases were the greatest cause of yield loss in 2019 as well, losses were much greater in 2020.

Table 4. Estimated wheat yield losses due to the five most significant diseases in Ontario, Canada in 2020.

Summary

Environmental conditions varied across the United States and Ontario in 2020, which affected the presence of and damage from many diseases. Losses were more than 53 million bushels greater in 2019 compared to 2020, possibly due to the above average temperatures and below average precipitation experienced by some wheat growing states.  

Disclaimer

The disease loss estimates in this publication were provided by members of the North Central Regional Committee on Management of Small Grain Diseases (NCERA 184) and the Western Wheat Workers (WERA 97). This information is only a guide. The values in this publication are not intended to be exact estimates of wheat yield losses due to diseases. The members of NCERA 184 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 at https://loss.cropprotectionnetwork.org/.

Acknowledgements

Authors

Andrew Friskop; North Dakota State University; Daren Mueller, Iowa State University; and Adam Sisson, Iowa State University.

Contributors

Kira Bowen, Auburn University; Travis Faske, University of Arkansas; Ron Meyer, Colorado State University; Alyssa Koehler, University of Delaware; Alfredo Martinez Espinoza, University of Georgia; Juliet Marshall, University of Idaho; Nathan Kleczewski, University of Illinois; Darcy Telenko, Purdue University; Kelsey Andersen-Onofre, Kansas State University; Carl Bradley, University of Kentucky; Paul “Trey” Price III, Louisiana State University; Martin Chilvers, Michigan State University; Jochum Wiersma, University of Minnesota; Tom Allen, Mississippi State University; Kaitlyn Bissonnette, University of Missouri; Mary Burrows, Montana State University; Stephen Wegulo, University of Nebraska-Lincoln; Gary Bergstrom, Cornell University; Christina Cowger, North Carolina State University;  Andrew Friskop, North Dakota State University; Pierce Paul, Ohio State University; Bob Hunger, Oklahoma State University; Albert Tenuta, Ontario Ministry of Agriculture, Food, and Rural Affairs; Alyssa Collins, Pennsylvania State University; Emmanuel Byamukama, South Dakota State University; Heather Kelly, University of Tennessee; Ken Obasa, Texas A&M University; Hillary Mehl, Virginia Tech; and Damon Smith, University of Wisconsin-Madison.

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

In addition to support from United States Department of Agriculture - National Institute of Food and Agriculture, this project was funded in part through the Grain Farmers of Ontario.