Production Blog

Free Calculator Figures Soybean Cyst Nematode Cost

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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You might be able to see SCN females by looking at roots, but it's best to get a soil test to confirm SCN density in a field. This is the time of year to pull those samples. (DTN photo by Pamela Smith)

There's no contest when it comes to the most destructive disease and associated yield losses. The soybean cyst nematode (SCN) is a hands-down winner every year. Now there's a simple tool to help estimate just how much the pest is costing in yield and bushels in any soybean field.

The SCN Coalition has developed a new SCN Profit Checker tool. Data from more than 25,000 Iowa State University field trial plots with SCN-resistant soybean varieties revealed a significant direct relationship among SCN egg numbers, reproduction of SCN populations on PI 88788 resistance and yield loss. That relationship was used to create an algorithm for estimating SCN's economic impact by field.


To use SCN Profit Checker, a farmer, agronomist or crop adviser provides the state name and the following field-specific information:

-- SCN egg count.

-- SCN female index on PI 88788.

-- Sand content of the soil.

-- Soil pH.


You've probably heard The SCN Coalition's slogan "Take the Test. Beat the Pest." Ideally, to use this new calculator, you plug in an HG Type test that provides the female index for the SCN population in your field. The more specific the information, the more accurate the estimate.

However, there's still a way to get a close idea if you don't know that detail by substituting a default female index. University scientists have developed these numbers for most states based on SCN female ability to withstand PI88788, the most common resistance in soybean varieties.

The tool also considers sand content and pH of the soil in the field because of the direct relationship with SCN reproduction. It uses yield expectation and targeted soybean price to calculate a yield and profit hit estimate from SCN.

Matt Gast, a soybean farmer from Valley City, North Dakota, who serves on the United Soybean Board (USB), said in a recent release from The SCN Coalition that the tool "makes a business case for SCN management." The hope is the tool will motivate more farmers to actively manage the pest and work with trusted advisers to develop a long-term management plan. USB helped fund the development of the SCN calculator.


The hot and dry weather conditions experienced lately are even more reason to put SCN in your crosshairs and plan to soil test for the pest this fall.

"We have data verifying that SCN is worse in hot, dry years," said Iowa State University nematologist Greg Tylka. "It's not just because plants are stressed from drought, but also because the nematode is reproducing much quicker, raising population densities." Read more about that here:….

Find the new tool that will estimate how much SCN is costing you here:….

Pamela Smith can be reached at

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