The only visible sign of SCN infection is the presence of white or yellow female cysts on the roots, but they might not be present at the time of sampling. Like all plant parasitic nematodes, SCN is a microscopic roundworm. Juveniles penetrate soybean roots and cause the formation of specialized feeding cells in the root's vascular system. These feeding sites divert materials needed for root growth to nourish the developing nematodes. Molting three more times before becoming adults, the SCN female juveniles lose their ability to move and swell to a lemon-shaped mature female.
White females become yellow as they age and then brown when they die.
The brown stage is the cyst for which the nematode is named. Each cyst can contain up to 500 eggs, but under field conditions, they usually contain fewer. The cyst, which protects the eggs from the soil environment, overwinters, and egg hatch begins in the spring. If the emerging juvenile nematodes cannot find a host plant within several weeks, they die. When soybeans are planted, exudates from developing roots stimulate more hatching and attract juveniles to the root systems.