The frequency of occurrence of winter annual weeds in Iowa fields has increased as more fields are managed with no-till production practices. And in recent years, scientists have discovered that the winter annual weeds purple deadnettle, henbit and field pennycress are moderate to good hosts for the soybean cyst nematode (SCN). Iowa growers and crop advisors are inquiring whether winter annual weeds could be supporting SCN reproduction leading to increases in SCN population densities. The answer depends on soil temperature.