Scouting for SCN in stunted or yellow soybeans,
OR
in a field that has not yet been checked for SCN

Recommended technique: Observe roots for the presence of SCN females.

When to sample
You can scout your fields for SCN by digging plants at least six weeks after planting until 3 to 4 weeks before harvest.

It is easier to observe the nematode on soybean roots early in the season, however, because the females and cysts occur on new roots that can be easily dug from the soil surrounding the base of the stem of the plant. Later in the season, adult SCN females and cysts appear on new roots that are located deeper down in the soil as well as farther laterally from the stem of the plant.

How to sample
The equipment for digging plants is common. You probably have everything you need in your barn or shed right now. A shovel and bucket of water are all you really need.

 A magnifying glass might be helpful, too, if you have one handy.

Use your shovel to dig up yellow and/or stunted soybean plants. You want to dig at least 6 to 8 inches away from the plant stem to make sure you haven't cut off much of the root system. 

Never try to pull up a plant to see SCN, you'll lose too much of the root system and strip off the nematode females as you pull the root system through the soil. Gently shake excess soil from the root system.

If the soil is heavy, or a lot of soil is still clinging to the roots, you may need to soak the root system in a bucket of water for a few minutes. Allow the soil to gently soak off the roots. Let the roots air-dry for a few minutes.

Check the root system for adult SCN females. They will be a lot smaller than the nitrogen-fixing nodules, about the size of the period at the end of a printed sentence. They will be white or light yellow and lemon-shaped.

The surface of the adult SCN females is smoother than the root surface and SCN females will be easier to see if the root has dried somewhat. SCN females are easier to see in dark soils than in light soils

Where to sample
If you are scouting a field that has never been checked for SCN, consider that SCN can be in a field for many years without the tops of the plants becoming yellow or stunted. For this reason, it is a good idea to include healthy-looking plants in your scouting.  A good place to start are in areas that have a higher risk for SCN, such as 

• near a field entrance
• areas that have been flooded at one time
• areas of high soil pH (greater than 7)
• areas where weed control isn't quite as good
• areas where the yield seemed to be a little low the last time soybeans were grown
• along fence lines where wind-blown soil accumulates.

What to do if SCN is detected

If when scouting your fields, you found SCN females on the roots, or if you weren't able to find females but still suspect SCN is present, you'll want to take soil samples and have them tested for SCN. A soil test is the best way to estimate the SCN population density in your field that will help to determine guidelines for managing SCN.

Adapted from SCN Symptoms and Soil Sampling slide set, courtesy of Greg Tylka, Iowa State University.
Questions? Please contact Greg Tylka, Iowa State University

Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.