NDSU Extension and the North Dakota Soybean Council will be again coordinating the soybean cyst nematode (SCN) testing program. There will be SCN soil testing bags available at the Extension office on a first-come, first-serve basis. Each grower can test up to three fields with the pre-marked soil testing bags. Results of the soil tests will be sent directly to the grower and the laboratory fees are covered by North Dakota Soybean Council checkoff dollars. NDSU does not have access to any personal information, just the reported egg levels and geospatial data which is used to generate a map of detected SCN levels in the state. The map accompanying this column was generated from the 2013-2019 SCN surveys. It should be noted that very low levels (50-200) could be false positives. As you can see from the map, Stutsman County has a few confirmed spots of SCN.
SCN is the most destructive soybean disease in the United States. It is a very small, microscopic worm-like nematode that penetrates soybean roots, robbing the plant of nutrients and water. SCN can even reduce nodulation which is vital for nitrogen fixation of the plant, resulting in the soybean plant producing fewer pods and reducing yield.
Above ground symptoms of SCN are variable and are difficult to distinguish between other production issues. The symptoms can vary from no symptoms to yellowing and stunting to plant death. In cases where no above ground symptoms were visible, as much as a 15-30% yield loss has been reported. Therefore, it is important to sample fields for SCN to monitor its presence. If SCN is detected when the population is still low, there are management options available to help keep the population low. However, if SCN is not detected early and the SCN population becomes very high, it can become nearly impossible to grow soybeans in that field ever again. This is why sampling is so important.
The best time to sample for SCN is this time of year either right before or right after soybean harvest because the SCN population is highest at the end of the season. Sample in areas of the field where SCN is most likely to establish first such as the field entrance, along fence lines, areas that have been flooded and areas where the soybean yield has been low.
SCN and soil fertility soil samples should be taken as separate soil samples. To take a SCN sample, take 10 to 20 soil cores in the root zone about 6 to 8 inches deep in a zig-zag pattern across the sample area. Place the soil cores in a container and mix. Place about one pint of soil into the soil testing bag and label the bag with a permanent marker. Since SCN are living organisms, it is important to store SCN soil samples away from sunlight and in a cool area until they can be sent into a lab. SCN soil samples should be sent into the lab immediately following sampling. For more information, contact the Stutsman County Extension office at 701-252-9030.