Soybean cyst nematodes are sneaky yield thieves. They enter your soybean plants at the roots, underground, feeding off your plant, and robbing nutrients and water as it grows. They don’t announce their presence aboveground with visible plant damage that you can scout for in the growing season. And once they’ve established themselves in your soil, they aren’t budging.

The first step in fighting the SCN thief is to sample your soil. But many farmers still aren’t being proactive in gathering soil samples to know for sure if they have SCN, and how big the SCN population might be. That’s why in October, BASF teamed up with the SCN Coalition to create SCN Action Month, to give away free soil test kits to growers, and cover up to $20 of the costs of the lab test.

From those samples, 70% showed a rise in damaging levels of SCN, says Jeremiah Mullock, BASF Agricultural Solutions product manager, seed treatment. “And average egg counts in the damaging level of around 2,000 eggs per 100 cc [cubic centimeters] of soil,” he adds. “This really illustrates that the SCN is out there, and we need to take action in building the plant to go into the next season. Pulling that soil sample really gives the litmus test of where to start your activities for the 2022 crop year.”

Kansas State University reports that as soybean acres expand across the western half of the state, so, too, does SCN. As of January 2020, SCN was reported in 59 counties that produce more than 85% of the state’s soybeans, according to the Oct. 2 Agronomy eUpdate. The farthest west was Finney County.

Fight back

Once SCN is in a field, farmers have had two options to fight back.

First, there are resistant soybean varieties, which include the PI 88788 SCN gene for resistance. The challenge is that this same source of resistance is used in about 95% of all SCN-resistant varieties, and the SCN populations are adapting to it, according to the SCN Coalition. Relying simply on planting resistant soybeans without soil testing to see if your SCN population is changing in the field is not good stewardship.

Second, using a seed treatment with a nematicide can add another layer of defense for your soybean crop. Mullock says BASF has a seed treatment nematicide, Ilevo, that kills SCN across all stages of its development. That prevents those nematodes from developing into adults and limits their reproduction.

While we can’t fully eliminate all SCN from a field, it’s about managing the population to a low level so that they don’t steal so much yield from the soybean plant, Mullock explains.

“If you grow corn for 10 years, there’s research that shows that if you go back to soybeans in the 10th year, that SCN is still going to be there and will still reproduce on soybean,” he says.

Other SCN management tips include:

• Soil-sample. It can’t be emphasized enough, but regularly soil-sampling fields keeps you on top of your SCN population numbers and gives you a starting point from which to make the rest of your management decisions.

• Clean equipment. SCN moves with soil, so it’s a good practice to clean any newly purchased used equipment thoroughly before introducing it into your field. And clean your equipment between fields to slow the spread.

• Rotate crops. Growing a nonhost crop like corn, wheat or other small grains between soybean crops can help you deprive the SCN population of their food source, and thus reduce the population before the next soybean crop.  

• Manage weeds. Some weed species can be a host for SCN.

BASF, the SCN Coalition, and Kansas State University Department of Agronomy contributed to this article.