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Symptoms and Signs
Key points to know
- Stunting and yellowing are above-ground symptoms of SCN.
- Early senescence of fields is an indirect above-ground symptom of SCN.
- There can be serious yield loss due to SCN without any obvious above-ground symptoms.
- Root stunting, discoloration, and fewer nodules are below-ground symptoms of SCN.
- You can see SCN females with the naked eye.
1. Stunting and yellowing can be above-ground symptoms of SCN
Fall SCN Sampling for Next Year's Crop
Recommended technique: Collect soil samples and have them tested for the presence of SCN.
When to sample
Fall is often the best time to sample as you plan for the next crop year. Sample as described below in the harvested field that is to be planted with soybeans next season.
Sampling to evaluate the success of an SCN management program
Recommended technique: Collect soil samples and have the SCN population densities determined.
When to sample
You can take a soil sample to check on the progress of a SCN management plan at almost any time of the year. But if you want to monitor the effectiveness of your SCN management program over several years, you should sample at the same point in the management program each time (say after a year of resistant soybeans or nonhost crop).
Sampling to determine if SCN is responsible for poor yields
Recommended technique: Collect soil samples and have them tested for the presence of SCN.
When to sample
Fall is often the best time to sample as you review harvest data. Take samples from the harvested soybean field, either in a zig-zag pattern or as part of a grid sample, as described below.
Where can I get more information about SCN?
A good starting point is the Soybean Cyst Nematode Management Guide published by the SCN Coalition in 1999. There are many excellent SCN-related resources available on the web. Many are accessable through our links section, or are available as the following ISU Extension Nematology Publications.
When should I get an SCN race test?
Under what conditions would an Iowa grower need to get an SCN race test done and how expensive is it?
What sort of crop rotation is recommended if I do find SCN in my fields?
Here at ISU, we have two management recommendation for SCN-infested fields. The recommendation given is based on the SCN egg population density (egg count) of the sample submitted.
Recommendation #1 - for fields with egg densities up to 5,000 eggs per 100 cc soil
We recommend that growers follow a six-year crop rotation scheme as illustrated below:
How high should the SCN population density (egg count) be before growing a SCN-resistant soybean variety?
Here at ISU, we have two management recommendation for SCN-infested fields. The recommendation given is based on the SCN egg population density (egg count) of the sample submitted.
Recommendation #1 - for fields with egg densities up to 5,000 eggs per 100 cc soil
We recommend that growers follow a six-year crop rotation scheme as illustrated below:
How many bushels per acre soybean yield loss can I expect for a given SCN egg population density (egg count)?
How many bushels per acre soybean yield loss can I expect for a given SCN egg population density (egg count)? In other words, what is the relationship between soybean yield loss in relation to the number of eggs per 100 cc of soil?
It is impossible to provide such precise information about the potential for yield loss because the amount of damage caused by SCN is very dependent on numerous interrelated factors including: