The soybean cyst nematode (SCN), Heterodera glycines, is a major yield-limiting factor of soybean in the United States and Canada (table 1). One thing contributing to the large amount of damage caused by SCN is its widespread distribution. The nematode has been found in every soybean-producing state in the United States except West Virginia and in all Iowa counties (figure 1) (Tylka and Marett 2017). And results of repeated random surveys of Iowa done in the 1990s (Workneh et al. 1999) and in the mid 2000s and in 2017 (Tylka unpublished) indicate SCN is present in 60% to 70% or more of the fields in Iowa.