Soybean cyst nematode of soybean
Damage from the soybean cyst nematode (SCN; Heterodera glycines) may not be obvious in high-yielding fields or during years when soil moisture is plentiful. However, yield losses of 40 percent or more are still possible. When symptoms are associated with damage, symptomatic plants usually occur in patches. Noticeable symptoms of SCN include stunting, slow or no canopy closure, and chlorotic foliage. Infected plants have poorly developed root systems and may have reduced numbers of nitrogen-fixing nodules. Signs of SCN include white females most readily seen in the field starting about six weeks after crop emergence. Dig roots and carefully remove soil to see the females. Soybean cyst nematode females (white specks) on soybean roots. Image: C. Grau
Aboveground symptoms of soybean cyst nematode infestation. Image: C. Grau
Soybean cyst nematode life cycle.
SCN survives in the soil as eggs within dead females, called cysts. These eggs can survive several years in the absence of a soybean crop. Conditions that favor soybean growth are also favorable for SCN development. High soil pH (7.0 to 8.0) may be used to predict where SCN is more problematic.
Resistant varieties are available. Resistant varieties are not resistant to all SCN populations and most resistant varieties contain one common source of genetic resistance. Rotating sources of resistance may help prevent development of more damaging SCN populations. Cropping sequences should include non-host crops (usually corn) and resistant soybean varieties. Cleaning soil from tillage and harvest equipment can help keep SCN from spreading to new fields. No-till practices may slow SCN movement and lower population densities. Nematode-protectant seed treatments may provide early season protection. Although proper management can greatly reduce SCN numbers, it is impossible to eliminate SCN from a field.