Soybean Cyst Nematode
Jamal Faghihi, Virginia Ferris
Appearance and Life History
Soybean Cyst Nematode (SCN) is a perennial pest of soybean in most soybean growing areas of the United States . This nematode is capable of reducing yields dramatically. Symptoms of SCN injury include presence of patches of yellow and stunted soybeans, with more pronounced symptoms in plants under stress and in sandy soils. Infected plants have poorly developed fibrous roots and with fewer Rhizobium nodules. Early in the growing season (6 weeks after planting), close examination of the roots may also reveal small, white to yellow spheres (bodies of female nematodes) attached to the root surface. These females are not much bigger than grains of coarse sugar, and should not be confused with the much larger Rhizobium nodules.
Stages in the life cycle include egg, 1st -4th stage juvenile, and cyst. The infective stage of the nematode is a microscopic worm-like second stage juvenile which hatches from an egg inside the cyst and moves into the soil when soil temperatures reach about 50°F in spring. The juvenile enters the soybean root, begins to feed, and eventually grows (by a series of molts) into a lemon-shaped white or yellow adult female which may contain 200-500 eggs. At this stage the nematode is loosely attached to the root by the head and neck. When the female dies, the cuticle turns brown and becomes a tough, protective package (cyst) for these eggs. This stage is very resistant to decay and can remain in the soil with viable eggs ready to hatch for many years. The life cycle of SCN takes 21-24 days under optimum conditions (soil temperature 75°-82°F); thus several generations are possible during each growing season.
Soybean plant with nematode filled cysts
Photo by J. Faghihi
While SCN can move through the soil only a few inches a year on its own, rapid spread can occur by the movement of infested soil. Cysts in soil adhering to equipment, soil peds in seed lots, or soil moved by wind and water can spread SCN to previously non-infested fields. How to Collect Samples
Soil samples should be collected in a zig-zag pattern within the field at a depth of 4-6 inches. Place in a plastic bag, a pint of soil collected from several areas of the field with a soil probe.
Include the following information on the outside of the bag:
- Location of the field
We refer to this information when responding to the submitter. Take as many samples as possible, as more sub-samples will increase the accuracy and chances of recovering one or more cysts if SCN is present. There is a $10/sample charge for processing soil samples, and payment is due after the sample is analyzed and results are mailed.
Send samples to:
The Nematology Laboratory
Department of Entomology
901 W. State Street
West Lafayette, IN 47907-2089
There is a $10/sample charge for processing soil samples.
Download Sample form
Rotation - Rotating soybeans with a non-host crop is the simplest and least expensive method to reduce SCN populations. Non-host crops include corn, small grains, and alfalfa. Host plants, on which the SCN population can maintain itself include all types of beans, lespedeza and hairy vetch. SCN is capable of reproducing well on several weeds; including henbit, purple deadnettle and common mullein. One year in a weed-free non-host crop can reduce an SCN population as much as 55 percent. However, since some of the eggs may remain unhatched in the cyst for years, it is impossible to starve all the nematodes.
Resistant Varieties - Almost every seed company now offers SCN resistant varieties. Even though the source of resistance for almost 97% of the current resistant cultivars is the same (PI 88788), these cultivars don't necessarily react the same way toward an SCN population. In 1996, we released a new resistant germ plasm known as CystX® . This germ plasm provides broad based and complete resistance to SCN populations and it has no yield drag. The yield potential of CystX® cultivar depends on yield potential of the nonresistant parent. There are several CystX® cultivars available in the market already, and more and better cultivars will become available for use by growers soon. CystX® cultivars in which all seeds possess all of the resistance genes from the original germ plasm provide complete resistance (no viable cysts will develop). Current CystX® cultivars are labeled either Gold or Silver. Gold cultivars contain a minimum of 95% CystX® seeds and Silver cultivars contain a minimum of 80% CystX® seeds.
If control is necessary, contact your state Cooperative Extension Service or contact Jamal Faghihi for control materials and rates.