The end of the field season is near and many producers are likely to spend some time watching the yield monitor as they harvest. This time is a great opportunity to identify spots in the field with unexplained yield loss. A potential explanation for these areas could be soybean cyst nematode (SCN). This small roundworm is the number one yield limiting biotic agent of soybeans in North America and is estimated to cause U.S. producers $1.5 billion a year. The reason this pest is so insidious is because SCN can cause up to 30% yield loss with no noticeable above ground symptoms. For this reason, SCN is an invisible threat that many producers do not know they have and are not actively managing.
As of January 1st, 2022, SCN has been identified in 59 Nebraska counties. However, this parasite is not found in every field of positive counties. In eastern Nebraska, SCN has been identified in all Counties. The average positivity rate of samples received from these counties is about 20%. SCN has likely spread to other counties in the region. However, few soil samples have been submitted from certain counties. We highly encourage more testing so producers can determine the status of individual fields.
Currently, the Nebraska Soybean Board in partnership with Nebraska Extension and the UNL Department of Plant pathology is sponsoring cost free soybean cyst nematode soil testing for samples from any Nebraska field. To take advantage of this program, contact your local extension office or request free soil sample bags be shipped to you at https://go.unl.edu/scnsample.
Effective soil sampling can be done by collecting SCN samples with a soil sampling probe or spade. Peak soil SCN levels will occur near the end of a soybean season. This makes October and November a great time to soil sample for SCN. Samples should be collected from the root zone to a depth of about 6-8 inches. Initial testing is encouraged in areas of unexplained low yield or areas of introduction risk like field entryways, previously flooded areas, field borders, or areas with increased sudden death syndrome or brown stem rot development. Place at least 2 cups of the composite soil sample in a bag and submit for SCN testing.
Once you have identified fields with SCN, there are four broad management recommendations. The first is to rotate between resistant varieties. The most common resistance sources available are ‘PI88788’ and ‘Peaking’. Rotation will help prevent your SCN populations from evolving to overcome resistance sources. The second management recommendation is to rotate to a non-host crop like corn or wheat. Rotation alone will not get rid of SCN, but it will help decrease their numbers in the soil. The third management recommendation is to consider the use of a nematode-protectant seed treatment. If you plan to use one, be aware that these should only be used in combination with a resistant soybean variety. The final recommendation is to continue to monitor SCN populations and levels through testing. As you make management changes, monitoring of SCN levels is important to determine if your management is effective. Sampling should be continued every 3-5 years to verify management effectiveness.
Many producers are experiencing some yield loss to SCN. Actively managing these populations will provide the opportunity to recover this yield. Remember that this pest is often invisible and soil testing is the only way to accurately identify and monitor the pest. If you don’t recall the last time you tested, it is time to test again. Request free soil sample bags today. Find more information at https://go.unl.edu/scninfo.