There's still time to test fields for SCN

There's still time this spring before planting to check fields for the presence of the soybean cyst nematode (SCN). This nematode is widespread throughout Iowa, but infestations can go unnoticed because obvious aboveground symptoms may not be visible for many years after the introduction of the pest into the field. Early detection of SCN infestations when population densities (numbers) are low is very important because it is much easier to keep low population densities of SCN in check than to decrease high population densities. If SCN infestations are discovered in fields in which soybean is to be grown in 2003, growers might be able to alter variety selection and plant SCN-resistant soybean in newly discovered, SCN-infested fields.

Soil sampling for soybean cyst nematode.

The only way to check fields for SCN before planting is to collect soil samples from fields and have them analyzed for the presence of SCN. The following are some guidelines for sampling fields for SCN:

  • Ideally, fields should be sampled using a soil probe.
  • Soil cores should be collected to a total depth of 6 to 8 inches.
  • Collect soil cores from 15 to 20 places in a sampling area.
  • Collect a separate set of soil cores for each 20 acres or so.
  • Combine and mix soil cores, and fill a sample bag with one cup or more of soil.
  • Label the outside of each sample bag with a permanent marker.

Many private soil fertility laboratories offer SCN testing of soil samples, as does the Iowa State University Plant Disease Clinic. The mailing address of the clinic is Plant Disease Clinic, Department of Plant Pathology, 323 Bessey Hall, Iowa State University, Ames, IA 50011-1020. The current fee for SCN analysis is $15 per sample.

Numerous Iowa State University Extension publications on SCN, including a list of SCN-resistant soybean varieties, can be obtained free of charge from county extension offices or on the Web at

This article originally appeared on pages 49-50 of the IC-490 (6) -- April 28, 2003 issue.

Updated 04/27/2003 - 1:00pm