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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:


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:


How do I interpret my soil test results?

Soil sampling for the soybean cyst nematode (SCN) has increased dramatically in the last couple of years. Several private soil fertility laboratories have begun to offer SCN soil analysis as a service. As growers continue to increase their sampling for SCN and begin to compare results from various fields and various laboratories, there are six questions that may be asked to help them interpret their soil sample results.


What is the best time to sample for SCN?

If a grower simply wants to sample a field to check for the presence of SCN, I'd recommend sampling the field after soybean harvest. The chances of finding SCN after a soybean crop are greater than sampling after a corn crop because soybeans are a host for SCN. Of course, if the grower discovers SCN in a soil sample taken from a field in which soybeans were just harvested and corn will be grown the next year, he or she also should collect another sample after the corn harvest in those fields if soybeans will be grown again following the corn crop.