Soybean cyst nematode is a widespread and serious pest of soybeans in Iowa. But many fields that are infested with the pest go undiagnosed because the nematode often does not cause obvious aboveground symptoms, at least not until population densities become extremely high.
Tylka, Greg, "Soybean cyst nematode will cause early senescence of soybeans" (2005). Integrated Crop Management News. 2401.