by Greg Tylka, Department of Plant Pathology
Many Iowa soybean fields may be infested with the soybean cyst nematode (SCN) but the infestations may not be known because SCN does not always cause obvious, above-ground symptoms. In fact, yield loss of up to 40 percent has been documented without above-ground symptoms occurring.
An easy, free and reliable way to check fields for the presence of SCN is to dig roots of susceptible soybean varieties. Carefully crumble away much of the soil from the roots, and look for the adult SCN females on the roots. The females appear as small, round, white objects on the roots and are about the size of a period at the end of a sentence.
We recently observed adult SCN females on soybean roots in research plots in central Iowa. The soybeans were planted in late May. SCN females will be apparent on young roots of susceptible soybean plants in Iowa through July and August, and probably early September this year. Roots should be checked for SCN females no earlier than four or five weeks after planting.
Additional information about the biology, sampling, and management of the soybean cyst nematode Web site.
Adult SCN females (yellow arrows) on soybean root. The two larger round objects (blue arrows) are nitrogen-fixing nodules.
Greg Tylka is a professor of plant pathology with extension and research responsibilities in management of plant-parasitic nematodes.