We encourage soybean and dry bean growers to sample for soybean cyst nematode. Below are some commonly asked questions and answers as prepared by the North Dakota State University Extension.
Q: Why should I sample?
A: Soybean cyst nematode can cause very high levels of yield loss before you see symptoms. Soil sampling is the best way to detect SCN. We have solid management tools for SCN on soybeans, so it is worth your time to look for it.
Q: Are my soybeans at risk for SCN?
A: While it is possible that any soybean grower in North Dakota could have SCN, the greatest risk is in the Eastern part of the state. The highest egg levels have been reported in Richland, Cass, Traill and Southern Grand Forks Counties. To date, SCN has been found in 19 North Dakota counties.
Q: Are my dry beans at risk?
A: Soybean cyst nematode can infect dry beans and SCN has been spreading into areas where dry beans are very common. While all market classes can be infected, recent data suggests that kidneys are the most susceptible market class and blacks might be the least susceptible. Pinto and Navy beans appear to be moderately susceptible.
Q: What’s the most common symptom of SCN?
A: Healthy looking soybeans. Typically, the first thing you will notice is a spot in the field that doesn’t yield well. After you have relatively high egg levels in a spot, you may start to see stunting or yellowing that appears in August.
Q: When is the best time to sample?
A: Just before or after harvest. The nematode population builds through the season, so sampling at the season ends maximizes your chances of detecting it.
Q: Where do I sample?
A: Anything that moves soil can move SCN. Consequently, we tend to find SCN in places where soil is deposited from other sources, such as the field entrance (soil moves on equipment), low spots (from overland flooding) or shelter belts / fences (from wind-blown soil). Additionally, consistently low yielding patches or yellow spots that appear in August may be a result of SCN. Lastly, SCN likes high pH; if you have a low yielding and yellowing high pH spot, it could be SCN.
Q: How do I sample?
A: Use a small soil probe or a shovel and aim for the roots. Take 10-20 small samples, mix up, and fill soil bag with the composite sample. Keep the bag relatively cool and get to the lab in the next few days.
Q: What do the results tell me?
A: Your results will be reported in eggs / per 100cc of soil. Essentially, this is how many eggs you have in about half a cup of soil. Positive egg counts mean you should begin managing SCN, negative egg counts mean you should be happy, and sample again when you put soybeans back in the ground. One point of note, very low numbers could be false positives (50 to 200). Resampling may be a good idea.
Q: How does the North Dakota Soybean Council (NDSC) funded sampling program work?
A: The NDSC has provided enough funding for up to 2,000 SCN grower samples. Go to the County Extension office, pick up several pre-marked bags, take some soil samples (directions are included) and mail to Agvise (the lab partner). You’ll get you results in the mail and the NDSC will pick up the bill.