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Sudden Death Syndrome of Soybean: Favorable Conditions and Request for Samples

By Dean Malvick, Department of Plant Pathology, St. Paul.

This growing season has been favorable for development of sudden death syndrome (SDS) in Minnesota. This disease is developing earlier than normal in my research plots in Waseca, and I expect it to become obvious soon in many soybean fields. The earlier it develops the more potential it has to cause significant yield loss. SDS has been spreading and we are requesting help to determine where it occurs in Minnesota. SDS has been concentrated in south central Minnesota in past years, but it could occur almost anywhere in the state.

Conditions favoring development

Thumbnail image for SDS June2010 MN distribution map-Malvick.jpg

The following conditions favor development of SDS:
  1. Planting early or a period of cool wet soil after any planting date
  2. Heavy and frequent rain in June and July
  3. Compacted soil and poor drainage
  4. High yield environments; this disease readily damages plants that are growing well
  5. Fields with high levels of the soybean cyst nematode (SCN)
  6. Susceptible soybean varieties, however, no varieties are completely resistant to SDS
  7. Fields where SDS has occurred before and the fungal pathogen (Fusarium virguliforme) is present in the soil. 

These conditions match what has occurred in many Minnesota fields this year. Keep in mind that this disease is spreading and it will likely appear in fields where it has not been seen before.  SDS cannot be managed this season, but steps can be taken to reduce it in the future.

SDS symptoms

Thumbnail image for SDS LEAF  in field 2007 MN Dakota County-MALVICK.jpg
Symptoms of Sudden Death Syndrome on soybean.

SDS usually appears first in low and compacted parts of fields and it tends to spread over time. Symptoms typically appear first in early August.  The symptoms on leaves begin as yellow, diffuse spots between veins in the lower to middle parts of the plant. The yellow spots expand between veins and the leaf tissue dies and turns brown. Leaves may be curled and detach from the petioles. Tan discoloration develops in the vascular tissue just under the surface of the lower stem. The pith remains white, which distinguishes SDS from brown stem rot (BSR).  SDS also causes root rot, and blue fungal growth can sometimes be seen on root surfaces in moist soil.

SDS survey

We request help this year in determining where SDS has spread  and poses a risk to soybean production in Minnesota.  We would like samples from any field in Minnesota that has confirmed or possible SDS.  If you or anyone you know sees plants that have SDS or are suspected to have SDS, please send them to me free of charge for diagnosis. We have new methods for confirmatory diagnosis. All sample information will be kept confidential. This work is supported by funding from the Minnesota Soybean Research and Promotion Council. 

Procedure for collecting and sending samples for SDS survey

  1. Collect 4 whole plants (include leaves, stems, and roots) that show leaf symptoms that look like SDS or could be SDS  from each field.
  2. Let me know that you have samples to send (an email message is preferred: and we will send a prepaid FedEx label to you for shipping the samples to me. We need the following information: Name, Address, Telephone number, and email address.
  3. Wrap plant roots in wet paper towels and place in a plastic bag, place whole plant in a paper bag, then place into one box. 
  4. Ship the samples to me at this address: Dean Malvick, Department of Plant Pathology, 495 Borlaug Hall, 1991 Upper Buford Circle, University of Minnesota, St. Paul, 55108.
  5. If you have questions, please call me at 612-625-5282 or send an email message to

Your help with this survey would be greatly appreciated.

More information

For more information, photographs, and a fact sheet on SDS, visit the Minnesota Crop Diseases web site.
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