The soybean cyst nematode (SCN), Heterodera glycines, is a widespread, destructive pest of soybeans in Iowa and much of the Midwest. Fortunately, SCN can be managed successfully by growing nonhost crops, such as corn, and resistant soybean varieties. But plants in many infested fields may not be stunted and yellow, at least not until SCN population densities (numbers) develop to high levels. It may take several years before noticeable symptoms of SCN damage become apparent.