Recently, data from several sources were compiled to determine the known distribution of the soybean cyst nematode (SCN) in Iowa. These data included results of analyses of more than 3,500 samples submitted to the Iowa State University (ISU) Plant Disease Clinic from 1994 to 1998 and nearly 400 samples collected from randomly selected sites in a survey conducted in Iowa from 1995 to 1996. Presently, SCN has been found in 85 of 99 Iowa counties. The counties where SCN has not yet been confirmed are located primarily in northeast and south central Iowa.
SCN probably is present in many of the "noninfested" Iowa counties; counties in southeast Minnesota and southwest Wisconsin, and almost every county in the northern tier of Missouri are infested. Unfortunately, only 19 samples have been submitted to the Plant Disease Clinic in the past four years for SCN testing from the 14 noninfested Iowa counties despite the known presence of SCN in adjacent counties. Clearly, growers and agribusiness personnel are not sampling for SCN in counties where the nematode has not yet been identified. This lack of sampling and testing for SCN is unfortunate because scouting for the nematode before symptoms appear leads to early detection. Identifying infestations before they have had years to increase is the key to successful management of this soybean pest.
There are numerous ISU publications available that contain information about SCN. The biology, life cycle, and recommended management of SCN are described in publication Pm 879, Soybean Cyst Nematode. Publication Pm 1649, Disease-resistant Soybean Varieties for Iowa , lists soybean varieties with resistance or tolerance to four major Iowa soybean diseases, including SCN. Publication IPM 47s, Scouting for Soybean Cyst Nematode, illustrates the recommended procedures for scouting for SCN. Finally, publication PD 32, Plant Nematode Sample Submission Form , is the form that should be submitted with soil samples to the ISU Plant Disease Clinic for SCN testing. Single copies of each publication are available free of charge from county extension offices or from the Extension Distribution Center  by calling 515-294-5247.
This article originally appeared on page 34 of the IC-480 (4) -- April 6, 1998 issue.