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Injury to soybeans from the soybean cyst nematode (Heterodera glycines Ichinohe) was documented as early as 1881 in Japan. The first report of the nematode in the U.S. came from North Carolina in 1954. It has since been detected in 26 states, including Nebraska. The question as to how soybean cyst nematodes got to the U.S. has not been answered definitively but it is speculated that it was introduced in soil imported from the Orient as a source of nitrogen fixing bacteria. It is difficult to asses when the nematode first arrived since field symptoms are often not evident. As a result, it can go undetected for many years. H. glycines has a wide host range consisting of many cultivated and weed species. It is separated into 16 races based on the ability to produce cysts (females) on four soybean cultivars. The nematode has a life cycle consisting of and egg stage, four juvenile stages and an adult stage. These nematodes over season as eggs contained in cysts and may survive in this state up to 11 years. The infective stage is the second stage juvenile. These juveniles penetrate the root area just above the tip and migrate to the vascular tissue. Specialized feeding cells are produced and the juveniles begin feeding. They are sedentary and this point and go through three more molts. When the adult stage is reached, males migrate back out of the root and females continue feeding and remain sedentary. They eventually become swollen and filled with eggs, taking on a white, lemon shaped form. The body of the female is extruded out of the root as it swells and the white female is visible outside the root. Its swollen body is much smaller than the nitrogen fixing nodules. As the female matures it turns yellow then brown the brown stage it known as a cyst and serves as the over wintering, egg containing, structure. The nematodes can develop over a wide range of temperatures but 24-28oC is optimum. H. glycines can complete as may as 6 life cycles in a single growing season. Factors that affect the number of cycles completed include planting date, host susceptibility, soil temperature and length of the growing season. It is also common to have "hot spots" of high nematode populations within the field. The nematodes are spread within the field and between fields as cysts in association with soil. They may be spread by wind, water, implements, migratory birds and soil peds (small soil aggregates) mixed with seed. Soybean cyst nematodes affect plant health by disrupting the transport of nutrients and water and providing entry sites for other soil borne pathogens.
Sinclair, J.B. and P.A. Backman, eds.. 1989. Compendium of soybean diseases, 3 rd ed. American Phytopathological Society. St. Paul, MN. 106 pp.
North Carolina State University
Non host crops of soybean cyst nematode include: alfalfa, barley, canola, corn, forage grasses, grain sorghum, melons, oats, red clover, sugar beet, tomato and wheat.
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This page was drafted by: Jane Christensen, Department of Plant Pathology, University of Nebraska-Lincoln
Disease images were provided by: Dr. David Wysong, Department of Plant Pathology, University of Nebraska-Lincoln
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This page is authored and maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln
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Copyright (C) 2003 J.E. Partridge, University of Nebraska-Lincoln. All Rights Reserved.