Scouting for Sudden Death Syndrome in Soybean

Disease cycle

The sudden death syndrome (SDS) fungus (Fusarium virguliforme) survives the winter as spores in crop residue and soil (Figure 1). Early in the season, the fungus infects and grows in soybean roots. Infection and colonization are favored by cool, wet soil conditions.The SDS fungus produces toxins in soybean roots that are transported to leaves. As a result, interveinal yellow and brown blotches appear on the leaves, typically after flowering. Foliar symptoms are more severe after frequent or heavy midseason rains.

Symptoms

Foliar symptoms

Leaf symptoms include yellow and/or brown lesions between the veins (interveinal chlorosis and necrosis) while leaf veins remain green (Figure 2). As the disease progresses, leaves die and prematurely drop from the plant (Figure 3). Pods and seeds also may abort.

Root and stem symptoms/signs

The woody tissue in the taproot (cortex) will be brown/gray while the upper portion of the center stem (pith) remains white (Figure 4). Blue masses of spores may be present on the root surface under wet conditions (Figure 5). Root symptoms and signs may be present even if foliar symptoms are not noticeable.

Others issues that look like SDS

Management

An integrated SDS management strategy is necessary since a single management tactic alone is not likely to provide adequate results. Management strategies include planting soybean varieties with resistance to SDS (Figure 9), using effective fungicide seed treatments, avoiding or reducing soil compaction, improving soil drainage in fields with recurring SDS, and maintaining proper pH and fertility levels.

Acknowledgments

Authors

Martin Chilvers, Michigan State University; Carl Bradley, University of Kentucky; Anna Freije, Purdue University; Loren Giesler, University of Nebraska; Daren Mueller, Iowa State University; Adam Sisson, Iowa State University; Damon Smith, University of Wisconsin; Albert Tenuta, OMAFRA; and Kiersten Wise, Purdue University.

Reviewers

Emmanuel Byamukama, South Dakota State University; Anne Dorrance, Ohio State University; Doug Jardine, Kansas State University; Dean Malvick, University of Minnesota; Sam Markell, North Dakota State University; and Laura Sweets, University of Missouri.

All photos were provided by and are the property of the authors except Figures 4 and 5 by Tom Hillyer, and Figure 6 by Tristan Mueller.

Sponsors

The Soybean Disease Management series is a multi-state collaboration sponsored by the North Central Soybean Research Program (NCSRP) through the Soybean Checkoff. 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. The authors thank the United States Department of Agriculture - National Institute of Food and Agriculture and the Grain Farmers of Ontario for their support. Contributors to this series come from land-grant universities in the North Central states and Canada. 

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.