SCN egg counts

Comparing SCN egg counts tells you if your management plan is working long-term. Work with crop advisers and Extension agronomists in your area to develop a management plan.

Harvest is the ideal time to test soil for soybean cyst nematode (SCN), and the SCN Coalition is encouraging soybean growers to know which fields have the yield-hurting pest and at what population densities.

SCN soil testing recommendations can vary by state, and some state soybean checkoff organizations, including Nebraska, have free soil sampling programs.

“Surveys funded by the soybean checkoff have found about 70% of the fields in Iowa have SCN,” Iowa State University nematologist Greg Tylka said. “Research also shows SCN can live in the soil for 10 years or more in the absence of soybeans. In other words, SCN can always be there, which is why farmers need to test their soil.”

In a new video series titled “Let’s Talk Todes,” Tylka and University of Missouri Plant Pathologist Kaitlyn Bissonnette explain why soil testing is the foundational element for managing SCN.

“If a grower doesn’t know he or she has it and isn’t actively managing it, potential yield can be lost,” he said.

If a field hasn’t been sampled after the last three soybean crops, taking soil samples after fall harvest may be a real eye opener, Tylka said.

With soil test results, growers can select SCN-resistant soybean varieties and determine if a seed treatment is needed, or they might alter the rotation and slot in a second year of corn to try and reduce SCN population densities even more.

Bissonnette says a SCN soil test can also demonstrate if a grower’s management is effective.

“After you have a baseline, coming back and testing soybean fields after harvest will tell you if modifications need to be made,” she said.

Once SCN is detected, it will always be there at some level, which is why Tylka encourages soybean growers to find it before populations explode.

“It’s always there and it’s always going to be reducing yield. It might be 3 or 4 bushels per acre or it might be 23 or 24 bushels per acre. But you won’t know until you test your soil,” he said.