A Farmer’s Guide to Soybean Diseases

Soybean (Glycine max [L.] Merr.) was once a forage and erosion control crop in the United States and Canada. However, it has become a major grain crop that is essential for food, feed, fuel, fiber, and other industrial purposes. As the national and global economies have evolved, the value of and demand for soybean have both increased, making it a profitable and important field crop in North America.

When a crop has high value and demand, protecting its yield potential is essential to reaping the greatest economic returns. Doing so means keeping the crop as healthy as possible—a goal that involves disease management. The cornerstone of effective disease management is accurate disease diagnosis. However, as farmers become more aware of how diseases affect soybean yields, they may be overwhelmed by the number of diseases that can be present on soybean and struggle to diagnose and manage diseases of importance. 

The purpose of A Farmer’s Guide to Soybean Diseases is to provide an overview of the soybean diseases that currently occur in the United States and Canada, with an emphasis on diagnosing diseases in the field setting. This guide explains the factors that make plants unhealthy, including plant pathogens. It also presents brief summaries of prevalent soybean diseases. Each disease summary includes sections that describe symptoms and signs of the disease, identify diseases and disorders with similar symptoms and signs, state the conditions that favor disease development, and review basic disease management options. 

The information presented for each disease is based on Compendium of Soybean Diseases and Pests, Fifth Edition, edited by G. L. Hartman et al. (American Phytopathological Society, 2015). However, additional information is also provided to aid in diagnosis—for instance, key diagnostic terms and disease distribution maps. A Farmer’s Guide to Soybean Diseases is not intended to provide an exhaustive discussion of every disease that occurs on soybean, and management recommendations are intentionally generalized to encourage readers to contact state and provincial Extension personnel or crop management specialists for region-specific management options.

Although this guide focuses on soybean diseases that occur in the United States and Canada, many other diseases have global importance. Some of these diseases are addressed in Chapter 7. Farmers should be aware of disease issues that may be of future importance to the United States and Canada.

Producing A Farmer’s Guide to Soybean Diseases truly has been a collaborative effort. Sixty-four contributors from more than 20 universities, agencies, and companies were consulted for their expertise with particular diseases. These contributors dedicated their time to editing sections, supplying images, and providing input on the development and direction of this book. The result is the first comprehensive overview of soybean diseases across the United States and Canada written with an audience of farmers in mind.

As soybean production practices advance and as environments change, so will the disease issues of importance. This guide is meant to be an evolving reference, and making updates and additions will be critical to maintaining its relevance. We encourage readers to offer feedback and suggestions to help improve this book, as we aim to improve the quality of disease references available to individuals involved in soybean production.

Quantity discounts are available for easy distribution to field representatives and other experts at your organization; VIP clients/customers in the soybean industry; colleagues in state and county Extension agencies; and fellow researchers and diagnosticians at your institution.