Soybean cyst nematode (SCN) is one of the most damaging diseases in soybeans. This microscopic plant-parasitic worm is a major threat to soybean production across the Midwest. Left unchecked at medium-to-high pressure levels, yield damage can reach as high as 90%.

Scouting and sampling for SCN is extremely important because the symptoms can be somewhat unclear, according to Dr. Mary Gumz, Pioneer Agronomy Manager.

“The classic expression of cyst nematode is a yellow and stunted oval patch in a field following any tillage lines,” Gumz said. “However, there are other conditions that mimic cyst nematode and SCN infestations can also be without symptoms. If you are unsure of the presence of cyst nematode in a field, the best plan is to pull a soil sample and send it into an accredited testing lab.”

And the best time to do that is toward the end of the growing season and leading into harvest. That allows the opportunity for populations to build up during the season and provides for a more accurate count. A good rule of thumb is to take the sample when the plants start dropping their leaves – it makes it easier to get through the field. Once you have an accurate assessment of SCN pressure levels in your field, you can better plan for next season.

Fall is the optimal time to sample soybeans for SCN.

Tips for More Effective Management

There are several management strategies for SCN. According to Gumz, the first is planting SCN-resistant soybean varieties.

“You need to be aware of the source of resistance though,” Gumz said. “For about the past 20 years, most of our resistant soybean varieties have been from a source of resistance called PI88788. We now have populations of soybean cyst nematode in the field that can overcome PI88788. So, you want to rotate between 88788 varieties with the other main source of resistance, Peking.”

Beyond planting and rotating resistant varieties, Gumz says there are additional ways to proactively manage SCN pressure in your fields, including:

If sampling turns up potentially damaging SCN pressure on your soybean acres, talk to your local field agronomist to put together a management plan for your acres. To read a recent study Gumz authored that documents the alarming results of SCN soil samples from more than 400 Midwestern soybean fields, see Soybean Cyst Nematode Populations Across the Midwest.  

¹ Data is based on average of comparisons in Pioneer Agronomy Science trials from 2012-2015 at 165 locations.

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