By Allen Wrather
Integrated Pest & Crop Management Newsletter
University of Missouri-Columbia
Vol. 16, No. 3
Article 3 of 7
March 17, 2006

Here is the situation: Soybean cyst nematode (SCN) is the worst pest of soybeans in the United States, and the situation isn’t getting any better. Yield suppression due to this nematode in the United States during 2004 was valued at about $820 million. However, these losses can be reduced by planting soybean varieties that have some resistance to SCN and by rotating soybean with corn, grain sorghum, cotton and certain other crops.

Unfortunately, selecting varieties with resistance to SCN in a field can be complicated. The following is a brief explanation of how to select SCN resistant soybean varieties. Some high yielding SCN resistant varieties of soybeans are available, but most are only resistant to one or two races of this nematode. Currently, SCN races 1, 2, 3, 4, 5, 6, 9, 10, and 14 were present in Missouri. Most companies use the wild type soybean numbered 88788 (resistant to SCN race 3 and 14) and/or the wild type soybean named Peking (resistant to SCN races 1, 3, and 4) as SCN resistant parents for developing varieties. In 1988, soybean cyst nematode in most Missouri fields could not attack varieties developed from these parents. However, in 1998, SCN in 54% of Missouri fields could attack varieties developed from these parents. Most companies still use these two parents for developing SCN resistant varieties, but some are now using other parents for developing SCN resistant varieties. If you planted an SCN resistant variety in 2005 and SCN damaged it, you should rotate the field to another crop for 2006. The next time you plant soybean in this field, select a variety that got its resistance to SCN from a different parent than the variety that was damaged in 2005. Information about soybean variety resistance to SCN is available at the University of Missouri Variety Testing web site, http://agebb.missouri.edu/cropperf/vartest. At this site, you should click on "2005 Soybean Results" and then in the next window click on "Characteristics of Varieties". Here you will find lists of varieties tested during 2005 and the source of SCN resistance used to develop each variety.

Crop rotation is useful for SCN control because the numbers of this nematode in the soil decline during years when corn, grain sorghum, or cotton is grown. The number of years a non host crop should be planted before planting soybean again will depend on the population of SCN in the soil.

The first step toward protecting soybean against SCN is to test the soil for the presence of SCN. Soybean growers should take soil samples and have them tested for SCN, and, if it is present, take steps to protect their crop against this pest. The SCN Coalition says this another way, "Take the Test. Beat the Pest." Information about taking and submitting soil samples for SCN analysis can be obtained from University of Missouri Extension Regional Agronomists or at the University of Missouri web site http://soilplantlab.missouri.edu/nematode.

Much of the research to develop SCN resistant varieties and information about the benefits of crop rotation for SCN management were funded by the Missouri soybean check off managed by the Missouri Soybean Merchandising Council. For more information about SCN management contact your University of Missouri Extension Regional Agronomists, read, Soybean Cyst Nematode: Diagnosis and Management, http://muextension.missouri.edu/explore/agguides/crops/g04450.htm, or read, Soybean Cyst Nematode Management Guide, http://planthealth.info/scnguide/.

Following these suggested procedures will give soybean growers a better chance of producing a profitable soybean crop in 2006.

Allen Wrather,
Professor University of Missouri-Delta Center