Soybean Cyst Nematodes, Still a Major Pest of Soybeans in Missouri

Soybean cyst nematodes (SCN) continue to cost Missouri producers millions of dollars a year. Surveys show that about 75 percent of the Missouri fields have SCN. Since a field may have 30 percent yield loss while showing no above-ground symptoms, without testing, producers may not realize they have a problem. The nematodes damage the roots, causing the plants to be stunted and, in severe cases, show potassium deficiency.  Potassium deficiency exhibits as yellowing along the leaf edges. 

Fields can be tested by sampling as you would for a soil test.  Here are a few tips for sampling for SCN:

1. Limit the size of the area being sampled: 10 - 20 acres is a good target.

2. Using a bucket and probe or shovel, walk the area in a W or Z pattern, sampling about 8 inches deep in the root zone between the rows. Take about 20 cores (with a shovel take ¼ cup of soil from near the shovel tip). Mix the cores well into a composite sample and bag about a pint of the soil for submission. Do not let the samples dry out! Nematodes are sensitive to heat. Do not leave samples in the sun or other areas of high temperature.

3. Label the plastic bag and ship it as soon as possible.

4. Fill out a submission form (available from our website or your local extension agent) or on a piece of paper indicate:

a.  Name, address, phone, and email (if you have e-mail, results can be sent quickly)

b.  County and cropping history

c.  Type of test: SCN egg count ($20), modified HG type test $75;

d.  The mailing address for the lab is:
Plant Nematology Lab, 23 Mumford Hall, University of Missouri
Columbia, MO 65211

Most of the soybean varieties in Missouri have the same source of resistance to the nematode. This has resulted in the resistance not working very well in some cases. If producers can’t rotate sources of resistance, they should at least rotate varieties. Besides using resistant varieties, growers can rotate to non-host crops such as grasses, alfalfa, corn and grain sorghum. Some preliminary research has indicated that cereal rye as a cover crop can help reduce SCN egg numbers. 

Several new seed treatment products have been released for SCN control. However, at this point, Missouri research has not indicated significant control from these products.  For more information about testing your soil for nematodes, contact your local University of Missouri Extension Center. 

Source: Pat Miller, Agronomy Specialist