By Greg Tylka, Department of Plant Pathology
The soybean cyst nematode has been known to exist in Iowa since 1978. The first Iowa finding was in Winnebago County. In the 1980s and 1990s, SCN was found for the first time in many different Iowa counties. By 2000, SCN had not yet been found in only nine Iowa counties. By the end of 2007, it had not yet been found or officially confirmed in only three Iowa counties – Allamakee, Ida, and Lyon County. Earlier in 2008, SCN was confirmed to be present in Lyon County.
Recent results reveal that SCN also is present in Ida County. Soybeans were grown in the greenhouse for one month in soil from an Ida County field and numerous SCN females were observed on the roots of the plants.
So there now is only one Iowa county, Allamakee County, in which there is no official record of SCN.
Counties in which SCN has been found in Iowa – December 2008. (SCN-infested counties in red)
Although SCN has been found in all but one Iowa county, not every field in the state is infested with the nematode. A comprehensive, random survey of Iowa currently is being conducted by ISU personnel in collaboration with the USDA National Agricultural Statistics Service (NASS) personnel and supported by soybean checkoff funding from the Iowa Soybean Association. In 2007, soil samples were collected from 205 randomly selected fields, and the nematode was found in 71 percent of the fields. A summary of the 2007 survey findings is available. The survey continued in 2008 and will be conducted again in 2009. Results of the 2008 survey will be made available in the near future.
If anyone knows of SCN in Allamakee County fields, they are encouraged to send soil samples from the fields to the Iowa State University Plant and Insect Diagnostic Clinic, 327 Bessey Hall, Ames, Iowa 50011, so that soybeans can be grown in the soil to verify that SCN is present.
Years of discovery of SCN infestation in Iowa counties – June 2008.
Counties in which SCN has been found in the United States and Canada – December 2008 (SCN-infested counties in red).
Greg Tylka is a professor of plant pathology with extension and research responsibilities in management of plant-parasitic nematodes.