- Soybean cyst nematode (SCN) is the most damaging soybean pathogen in many areas. Infected plants may or may not show foliar symptoms.
- Heterodera glycines is the soybean cyst nematode. Numerous different types (Hg types) of the nematode occur that are pathogenic to soybean varieties with different sources of resistance. Host range includes soybean and numerous legume and weed species.
- The disease is best diagnosed by looking for tiny white to yellow lemon-shaped cysts on the roots, beginning toward the end of June and then throughout the flowering period.
- Aboveground symptoms are not always present, even though yield loss due to SCN may be significant.
- In fields with very high levers of SCN, heavily infected plants may be stunted and yellow or chlorotic, particularly under low fertility or drought conditions.
- Badly infested areas may be oval to somewhat elliptical in outline. Such areas show the most severe damage in the center, with less damage toward the margin.
Conditions Favoring Disease
- Continuous susceptible soybean or susceptible soybean grown every other year in rotation
- Moisture and fertility stress can enhance the disease.
- The first step is to test soil samples to determine if SCN is in a field.
- Sampling Procedure:
- Examine fields 6 weeks after planting until late August. Dig (do not pull up) and carefully examine for the presence of cysts. If cysts are detected on plants, soil samples can be collected to determine population levels more accurately.
- Soil samples should be collected to determine if cysts are present. Samples can be taken at any time, but most effective for making management decisions is to sample fields that will be planted to soybean in the next season, after the fall harvest. Then to 20 soil cores per 10 acres for a composite sample are adequate for testing. Samples collected in the same way can be submitted for egg counts to monitor SCN populations.
- Soybean should be rotated with nonhost crops.
- Resistant soybean varieties should be planted.
- Rotate with different resistant varieties and different sources of SCN resistance when possible.
- Manage weeds, moisture, and fertility to reduce plant stress.