The soybean cyst nematode (SCN) has plagued Iowa soybean production since the 1980s. It continues to be a serious yield-limiting pest of soybeans throughout the state, causing yield losses directly as well as indirectly by intensifying other serious soybean diseases. SCN is widely distributed throughout the state. The nematode has excellent long-term survival and its population densities build up each year that susceptible soybeans are grown, regardless of the rainfall and temperature that occur during the growing season. Up to 40% yield loss can occur without the appearance of any aboveground symptoms (Wang et al., 2003).