Ames, Iowa
November 25, 2002

Soybean producers should consider more than yields when choosing varieties that help manage soybean cyst nematodes, according to Iowa State University nematologist Greg Tylka.

Growing soybean cyst nematode-resistant soybean varieties is one way producers can reduce the pest's population in the soil, Tylka explained. But some varieties work better than others.

"Many people may believe that all SCN-resistant varieties control the nematode equally, but that's simply not so," Tylka said. "Some high-yielding, SCN-resistant soybean varieties allow considerably more SCN reproduction than other high-yielding varieties, and increased SCN numbers will reduce the soybean yields for years to come."

SCN-resistant varieties are evaluated each year by research and extension personnel in Iowa and other
Midwestern states to help growers select the ones to grow. The results from the 2002 variety trials are
beginning to be released.

"Everyone evaluates SCN-resistant varieties for yield and other agronomic traits, but hardly anyone provides information on how much nematode reproduction occurs on the varieties," Tylka said.

Ignoring the varieties' ability to control soybean cyst nematodes is "risky" because SCN can quickly increase in numbers and live a long time in the soil, he added. Producers also need to consider ratings of SCN control gathered in fields instead of greenhouses.

"The field environment plays a significant role in how SCN reproduces on the soybean host and, thus,
greenhouse results often do not reflect what will happen in the field," Tylka said.

Tylka's staff conducts the Iowa State SCN-resistant Soybean Variety Trials at numerous locations throughout Iowa each year to provide information on how resistant soybean varieties affect SCN numbers.

"It takes us a month and a half after we harvest and determine yields to process and count the thousands of soil samples collected from our variety trial plots," Tylka explained, "but the information contained in our report is not available anywhere else. We believe the report is worth waiting for."

Results from the 2002 Iowa State University SCN-resistant Soybean Variety Trials will be available in
January 2003 from county extension offices (publication IPM-52) and on-line at:  www.isuscnvarietytrials.info. Additional information about SCN biology and management from Iowa State University can be found at: www.soybeancyst.info.