Soybean Cyst Distribution In North Dakota

During the last two growing seasons, Soybean Cyst Nematode (SCN) has been confirmed in seven additional North Dakota counties. This brings the total number of counties known to be infested with SCN to 19; all of which are in the Eastern half of the state (Figure 1).

 

 

The data to color this map green came from several sources. Confirmations prior to 2012 came from a survey project funded by the North Dakota Soybean Council, a partnership with the National Agriculture Statistics Service, and information and test results provided to us by growers, Extension Agents, private agronomists, crop consultants and other agricultural professionals.

 

 

Confirmations in 2013 and 2014 came primarily from samples submitted through the SCN sampling program operated by the NDSU Extension Service and funded by North Dakota Soybean Council. Some additional data came from the North Dakota Department of Agriculture. The SCN sampling program was designed to provide free SCN sampling to growers throughout the state. Participants could pick up sampling bags at their County Extension office, submit the sample to Agvise (who did the tests) and then would receive their results directly through the mail. In the process, Dr. Markell received egg count GPS data. We then constructed maps with the results.

 

In 2013 and 2014, nearly 800 samples were submitted, and approximately 1/3 of them showing up positive. While the high level positive samples are clearly positive, it is possible that low level positives (for example, 50 eggs/100cc) could be false positives. This is simply because other nematodes lay eggs in the soil, and it is not possible to differentiate SCN eggs from other cyst nematode eggs by morphology. To account for this, we ‘confirmed’ counties as positive only if multiple samples showed up positive, and at an egg level we are comfortable with being ‘real’; typically over 50. As a result, seven additional counties are being called confirmed positives in 2013 and 2014. Several additional counties had positive samples, but we are not yet willing to call them confirmed positives because of insufficient sample number or egg levels too low for us to be confident.

 

While it may be alarming that SCN is occurring in so many counties, it is important to realize that the vast majority of samples received outside of Cass, Richland and Traill, are negative (Figure 4). Additionally, when positive samples are received outside of Cass, Richland and Traill, the egg levels are typically quite low. Consequently, North Dakota soybean growers are in a very good position to manage SCN. Early detection and pro-active management with crop rotation and genetic resistance can prevent or mitigate damage from SCN.