The soybean cyst nematode (SCN) was first discovered in Iowa more than 35 years ago, in Winnebago County in 1978 to be specific. The nematode is widely considered to be the most damaging pathogen of soybeans in Iowa. Results of random surveys of the state funded by the soybean checkoff and conducted in the mid 1990s and again in the mid 2000s indicate that SCN is likely present in 75 percent or more of Iowa fields. SCN has the potential to increase in numbers very quickly, it can cause 50 percent or greater yield loss, and it can survive dormant in the soil for a decade or more in the absence of a host soybean crop.