Sioux Falls Regional Extension Center News

By Connie L. Strunk

Plant Pathology Field Specialist

Sioux Falls Regional Extension Center


Fall sampling for soybean cyst nematode detection is encouraged


With soybean harvest finished or just about wrapped up for most, now is the time to start sampling for soybean cyst nematodes (SCN). As you were combining your soybean fields, did you notice any discrepancies in your yield? Did some areas yield lower than others? Have any of your soybean fields consistently not yielded where you thought they should? Have you ever sampled/tested for SCN?

SCN silently robs yields causing significant yield losses without displaying obvious symptoms. Unfortunately when SCN is introduced in the field it can never be completely eliminated; however, SCN can be managed to keep SCN population below injury level. By the time one soybean cyst is observed on the soybean roots or in the soil sample, it is probable more cysts are occurring out in the field. One cyst can contain up to 500 eggs and 2- 3 cyst cycles can occur in a growing season.

SCN sampling allows you to determine if SCN are present and if so at what population levels. Soil sampling for SCN can occur at any time throughout the year as long as the soil is not completely saturated or frozen, but to get a good idea on your true numbers sampling in the fall after harvest is recommended.

Areas to target and sample include: field entrance, along fence lines, low spots, previously flooded areas, waterfowl activity areas, high pH areas, and low yielding/stunted areas of the field. Samples should be collected to a depth of 6-8 inches and ideally collect 20 soil cores from the sampling area and mix them together to develop your sample for submission. Again do not sample from wet or frozen ground.

Through a grant provided to SDSU Extension by the Soybean Research and Promotion Council, SCN testing is free for all South Dakota growers. We will have soil sampling information and bags available for pick-up at the Sioux Falls Regional Extension Center but you can always use a paper bag or plastic bag of your own as long as the soil is dry. You can always request additional soil sampling bags from me at the Sioux Falls Regional Extension Center by calling (605) 782-3290.

Soil samples may be submitted for SCN testing to the:

SDSU Plant Disease Diagnostic Clinic

1205 Jackrabbit Drive

Box 2108

Brookings, SD 57007

If SCN is found in your fields you want to keep the numbers from building up. The first step in SCN management is rotation. Rotate to non SCN host crops such as corn, alfalfa, small grains, sunflowers, flax, and canola. Cysts can remain in the soil for ten years or longer. The second management step is the use of resistant SCN cultivars. Another step would be to make sure and rotate your soybean resistant cultivars so SCN does not have a chance to overcome a given resistance.

For more information, please feel free to contact me at the Sioux Falls Regional Extension Center, 605-782-3290, or by email at If you have any other questions related to SCN or plant diseases please don’t hesitate to contact me. I look forward to seeing you this upcoming winter at various farm shows, PAT/CATS, crops clinics, etc.

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