Heterodera glycines The Soybean cyst nematode Eggs and juvenile female on root Damage to Soybean. Soybean cyst nematode is one of the most important diseases of soybeans. Yield losses can be severe, approaching 100 percent in localized areas of infested fields. Even small populations can cause serious damage.  Biology.  In its juvenile form, Heterodera glycines penetrates soybean roots.  Those that become females lose the ability to move, enlarge into a lemon-shaped "white female," which breaks through the root surface, dies, and turns into a brown cyst or egg case. Ecology. SCN is relatively new to the midwest.   It was first found in the U.S. in 1954,  probably inadvertantly introduced in soil imported from the Orient. Symptoms.  Field symptoms of soybean cyst nematode include yield loss,stunting and chlorosis. The only unique symptom of SCN infection is the presence of white (or yellow) females on roots.  Damage to other crops. Heterodera glycines is a pest on beans and other legumes, as well as numerous other plant species. Control. Crop rotation and nematicides have limited success, but once present in the soil, SCN can never be eliminated. Links and References.  Soybean Cyst Nematode