A major factor limiting soybean production in Iowa is parasitism by the soybean cyst nematode, Heterodera glycines. Soybean cyst nematode is now known to be present in 48 counties within Iowa. It is very likely that the nematode is present in many other counties as well, but the nonspecific nature of the above-ground symptoms of soybean cyst nematode damage makes early identification or diagnosis of infestations difficult.