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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

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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).

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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:

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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:

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