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The soybean cyst nematode injures soybean roots, which can cause stunting of the plant. Also, plants may be yellow (chlorotic) due to a reduction of root nodulation. However, often times substantial yield loss occurs in the complete absence of noticeable stunting or yellowing of the plants, particularly in the Midwest.
Adult females and cysts (dead females) of this nematode are lemon-shaped and vary in color from white to brown. The females and cysts are filled with eggs from which juveniles hatch, penetrate the roots, and develop into adults in 14-21 days. As they develop, the female nematodes enlarge until they rupture the root, but maintain root attachment for some time, and then die and fall off in the soil. Soybean varieties resistant to the soybean cyst nematode are widely available in all maturity groups. Although soybean cyst nematode populations (formerly called races) vary in their ability to feed and multiply on resistant soybean varieties, most populations usually are controlled adequately with resistant varieties. Rotation to nonhost crops (e.g. corn, cotton, sorghum, and wheat) is helpful in reducing nematode populations. A few nematicides also are labeled for control of soybean cyst nematode, but efficacy and economics should be carefully considered when employing this management option. Above-ground symptoms of soybean cyst nematode damage do not occur reliably and are not unique. Infestations of soybean cyst nematode can be accurately diagnosed by observing females and cysts on soybean roots during the growing season or by detecting cysts, eggs, and/or juveniles of the nematode in soil samples collected at any time of the year. |
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