Soybean cyst nematodes could be keeping a lid on top soybean yields without you knowing it. That’s why companies often suggest the first step is to sample your fields to see if SCN are present.

Chad Threewits is an agronomic service representative for Syngenta in Indiana. He recently took time for an exclusive interview with Indiana Prairie Farmer.

People once thought soybean cyst nematode was only a problem on sandy soils. Is that true? No. Soybean cyst nematodes can be in any soil, including prairie soils and level, dark soils. They’ve been found in almost every county in Indiana. Sometimes people who farm sandy soils know they have a problem because nematodes have caused visual symptoms and yield loss, but they can be almost anywhere.

How do you know if soybean cyst nematodes are a problem in your fields? First, ask yourself if you’re having trouble getting soybean yields as high as you think they should be. If they seem to hit a barrier, one possible contributor is cyst nematode. They can damage roots without showing visible symptoms. If you have fields where you believe soybean yields ought to be higher, they’re good candidates for soil sampling for nematodes.

How do you take samples? It’s similar to soil sampling for soil tests, except you want to take cores next to the soybean row if it’s after soybean harvest. You want to get some roots in the sample. You also want to take at least 15 cores at random in a zigzag pattern across a 20-acre area. Soybean cyst nematodes often occur in hot spots. If you only sample in one or even a few locations, you may miss hot spots.

What do you do once you have collected samples? Obtain packaging instructions and cost information for a university lab. Purdue University has a nematology unit that offers soil sampling. Visit extension.entm.purdue.edu/nematology/service.html. What you get back are numbers representing nematode counts in a specific volume of soil. A moderate number might be 500 to 1,000. That’s definitely high enough to indicate that you need to manage for cyst nematodes. I have seen counts as high as 25,000. In those cases, you probably already know that you have a problem.

When can you sample for nematodes? You can sample any time of the year, preferably when the soil isn’t frozen. The peak time is after harvest before a frost, but you can even sample in the spring. You can also sample in cornfields that will be going to soybeans the next year.

Why are you alerting people about sampling now? Syngenta recently received approval for Clariva Elite Beans, a seed treatment which includes many ingredients, including Clariva, which is a biologic control for nematodes. Clariva has been available before, but it had to be added separately. If you have cyst nematodes, it is another management tool you can use.

Editor’s note: Watch for the second part of this story about SCN on Oct. 24. Other seed treatment products for SCN besides Clariva and Clariva Elite Bean are on the market.