The intensity of the symptoms is influenced by the age and vigor of the soybean plants, the nematode population density in the soil, soil fertility and moisture levels, and other environmental conditions. Soybean cyst nematode damage usually is more severe in light, sandy soils but will occur readily in all types of soil. O ne can not rely upon above ground symptoms for identification of soybean cyst nematode infestations. If soybean yields in a particular field have leveled off or decreased for no apparent reason or if soybean cyst nematode has been confirmed on nearby land, more thorough examination of plants for below ground symptoms and a soil analysis are needed. Below-ground Symptoms M ost below ground symptoms of soybean cyst nematode injury are not unique.
Roots infected with the nematode are dwarfed or stunted.
Soybean cyst nematode also decreases the number of nitrogen fixing nodules on the roots, and infection of roots by soybean cyst nematode may make the roots more susceptible to infection by other soil-borne plant pathogens. Often, it is difficult to recognize roots as being stunted and having fewer nodules unless some uninfected soybean roots are available for side by side comparison. T he only unique sign of soybean cyst nematode infection is the presence of adult female nematodes and cysts on the soybean roots. Females and cysts appear as tiny, lemon shaped objects which are white initially but turn yellow, then tan to brown as they mature. The females and cysts can be seen on infected roots with the unaided eye, although observation with a magnifying glass usually is much easier.