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Sudden death syndrome (SDS) is beginning to show earlier on soybeans in Minnesota and Iowa this year. In South Dakota, the recent cool, wet conditions can favor SDS development. Now is a good time to scout soybean fields to see if there are any disease issues including SDS that may need attention.
SDS usually shows up in spots or scattered areas throughout the soybean field. The disease generally becomes visible as the soybean plant starts to develop pods (R2 – R3 stage). Symptoms of the disease first appear as yellow between the leaf veins (Figure 1). This leaf tissue dies and turns brown while the leaf veins remain green. As the disease progresses the yellow and brown areas become large irregularly shaped lesions (Figure 2). Leaves eventually fall off of the soybean plant. The earlier SDS symptoms develop, the greater the potential for yield loss.
While there are no in-season options available for SDS management, research is being done at SDSU on developing management strategies for reducing the risk of the disease. Seed treatments are currently being evaluated for SDS management and the research is supported by the South Dakota Soybean Research and Promotion Council. At this time, the best way to manage SDS is to plant the most resistant varieties possible. Check with your seed company to get information on which soybean varieties for South Dakota are fairly tolerant to SDS.
There may be other diseases on soybean that look like SDS. For more details and photographs, please refer to Scouting for soybean stem disease.
Brown stem rot (BSR) may have foliar symptoms similar to that of SDS, but the two diseases can be distinguished by splitting the soybean stems. If the inner portion of the soybean stem is white, the field most likely has SDS. In contrast, BSR causes browning of the inner stem tissue (pith).
Stem canker produces reddish brown-colored lesions that begin at a node on the soybean stem and work their way up or down the plant. As the plants age, stem canker lesions can darken and cause the plant to die prematurely.
Charcoal rot is best diagnosed by splitting the soybean stem in half and looking for gray discoloration and black spots (
Chemical burn can also produce foliar symptoms similar to SDS; however no signs of pathogens will be found on the soybean plants and the roots would most likely appear healthy.
Request for Soybean Samples
If you identify SDS in your field or may have SDS-like symptoms on soybean and are not sure what the disease may be, please consider sending samples to the SDSU Plant Science Department. Samples will be used in SDS research conducted by Mr. Paul Okello (a graduate student supported by the South Dakota Soybean Research and Promotion Council).
The best way to submit soybean samples is:
Collect at least 3 plants (including roots) showing SDS or SDS-like symptoms. The plants should not be wet with rainfall or dew. If they are wet, allow the sample to dry before they are boxed.
Please include information on location (GPS, county), tillage, growth stage and previous crop.
Once soybean plants are dried, send soybean samples in an e
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