A major factor limiting soybean production in Iowa is the soybean cyst nematode, Heterodera glycines. Soybean cyst nematode is now known to be present in 85 Iowa counties. It is very likely that the nematode is present in many other counties as well, but the nonspecific nature of the aboveground symptoms of soybean cyst nematode damage makes early identification or diagnosis of infestations difficult. Results of recent random surveys indicate that the nematode likely exists in more than 70% of Iowa fields (Workneh et a!., 1998).