Plant-parasitic nematodes are microscopic worms that live in the soil and feed on plant roots. Nematodes that feed on corn occur in almost every field in Iowa, but most do not reduce corn yields measurably until they increase to high population densities (numbers). Fall is not a recommended time to check fields for damaging population densities of nematodes that feed on corn. The ideal sampling times and methods for nematodes that feed on corn were discussed in an earlier article in ICM News. The soybean cyst nematode (SCN) is considered by many to be the most damaging pathogen on soybeans in Iowa, the Midwest and the United States. SCN has a very unique biology that allows it to cause great yield loss (greater than 50 percent), to reproduce very quickly and to survive 10 years or more in the absence of a host crop.