Updated June 29, 2018:
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Why was this research conducted?
Soybean Cyst Nematode (SCN) is the most yield-limiting soybean disease in the U.S. and was first reported in North Dakota in Richland County in 2003. By 2012, SCN was confirmed in a dozen counties. In 2013, NDSU Extension and the North Dakota Soybean Council developed an SCN sampling program to encourage growers to sample their fields.
Why is this research important to North Dakota soybean farmers?
SCN can cause 15-30% yield loss before any above ground symptoms are apparent, making proactive detection by soil sampling extremely important. In this program, SCN sample bags and instructions are distributed to every County Extension office, at field days and by request. Growers send samples to the lab (free of charge), receive their data in the mail and maps of SCN distribution in the state are created (all other grower information is kept confidential).
What are the findings of this research?
710 samples were received in the fall of 2017. 237 of the 710 samples were positive (approximately 33%) and egg counts ranged from 50 eggs/100cc to 55,400 eggs/100cc. Notably, very low egg counts (50 or 100 eggs/100cc) could be false positives. To better visualize SCN distribution in North Dakota, all data from 2013 to 2017 were combined (Figure 1). In 2017, a notable increase in samples from Grand Forks County were recorded, but while some egg counts in the county were very high most were negative. Enough data points were collected from 2013 to 2017 that ‘heat maps’ were created for the southeast and southcentral counties in North Dakota (Figure 2).
Benefits to the North Dakota Soybean Farmers:
Since 2013, over 3,000 sample bags have been submitted by growers, of which approximately 1/3 were positive for egg counts. This likely represents the sampling of hundreds of thousands of soybean acres in the state. While the level of yield loss is dependent on many factors, susceptible soybeans planted on SCN ground commonly experience a 40% yield loss when conditions are favorable for the disease. Early detection with this program, along with use of management tools, has very likely saved North Dakota soybean growers many millions of dollars since 2013.