Just because you're planting a soybean resistant to soybean cyst nematode doesn't mean your soybeans won't be affected by the pest.
Shaun Casteel, Purdue University Extension soybean specialist, pointed out to visitors to the Purdue Agronomic Research Center that cyst nematodes are overcoming resistance to some on the most common strains of resistance on the market.
What that means is that if you plant a resistant variety, you could still see symptoms of the disease, especially in a field with severe cyst nematode pressure.
There are only two ways to know if the field has a history of severe cyst nematode pressure. One is to have had problems when growing soybeans with cyst nematodes in that field at least once before. The other is to pull a sample and have a lab test for cyst nematodes.
This is a good time of year to pull soil samples in suspect fields. It's also the most accurate way to track whether cyst numbers are increasing, leveling off or decreasing over time, assuming you either sampled in the past or resample in the future.
Traditionally soybean cyst nematodes have caused damage on sandier, lighter soils in north-central and in parts of southern Indiana. But testing has shown that they are in many other fields.
The problem with soybean cyst nematode is that they can cause yield damage without you ever seeing the symptoms. Sometimes the symptoms express themselves in severe cases, but sometimes they don't.
The only clue then is reduced yield compared to past years or else soil sampling results from samples taken exclusively to test for soybean cyst nematode.
If you suspect cyst problems, dig some plants and look for cysts on roots. They are distinctly different than nitrogen-producing nodules. You may want to talk to your seedsman about other types of resistance they have available, if any, if varieties you have used in the past don't seem to be standing up to the cyst pressure as well now.