Consider Sampling for Soybean Cyst Nematode By Laura Sweets and Bob Heinz

We usually think of fall or after soybean harvest as good times to sample for soybean cyst nematode (SCN). But samples can be taken at any time of the year. SCN damage can be more severe when plants are suffering from moisture stress. When making field calls related to yellow soybean plants, stunted soybean plants or dying and dead soybean plants right now, consider collecting a soil sample for SCN analysis. SCN could be contributing to the symptoms occurring in many fields throughout the state and having an SCN egg count done now would verify that and would give information to use in making decisions on crop rotation, variety selection, etc. for next season.

The SCN egg count test is what most soybean growers need. If you haven’t had a test run in 5 to 10 years, an investment of $15 and a bit of time is little for the peace of mind" or the knowledge that a problem is making a comeback. Sample a field that you notice is slipping in yield, or the one that had high egg counts years ago. If the egg count is medium or high, you may want to sample your other fields.

Because SCN egg counts are only as good as the sample taken, here are some hints to improve sampling for SCN:

1. Limit the size of the area being sampled: 10 acres is a good target.
   
2. With your bucket and probe or shovel in tow, walk the area in a W or Z pattern, sampling about 8 inches deep between the rows. Take about 20 cores with a shovel (take 1/4 cup of soil from near the shovel tip). Mix the core well into a composite sample, and place about a pint of it in a plastic bag for submission.
   
3. Label the plastic bag, avoid storing it in the sun, and ship it as soon as possible.
   
4. Fill out a submission form (available from our Web site or your local extension agent) or on a piece of paper indicate:
   
   • Name, address, phone, and email address (if you have e-mail, results can be sent quickly.)
     
   • County and cropping history
     
   • Type of test: SCN egg count ($15), HG type race test ($50 instate, $100 out-of-state), or complete nematode analysis ($20)
     
   • The mailing address for the lab is:
     Extension Nematology Lab
     46 Agriculture Building
     University of Missouri
     Columbia, MO 65211
     

The HG type race test is a good choice for the grower who has high egg counts after growing resistant lines for years. This test indicates the HG type (or race) of SCN in the field, and what sources of resistance would be good to choose when buying seed. The Web site below gives a comprehensive listing of the "sources of resistance" for commercial soybean lines: http://www.ag.uiuc.edu/~wardt/cover.htm.

The complete nematode analysis is a count of the worm stages of all the plant parasitic nematodes in the sample. (It does not give an SCN egg count.) This test is important for southeast Missouri growers who may have the root knot nematode as well as SCN.

The Extension Nematology Lab Web site gives more information about how to sample, the tests provide available, and how samples are actually run in the lab. A submission form can also be downloaded from the following Web site: http://soilplantlab.missouri.edu.

Laura Sweets
Plant Pathologist
573-884-7307

Bob Heinz
Research specialist, Extension Nematology Lab Coordinator
573-882-0816