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The widespread drought made 2012 a banner year for SCN in Iowa. “In 25 years I’ve never seen as much reproduction as we did last year,” says Greg Tylka, Iowa State University (ISU) Extension nematologist and plant pathologist. “We don’t understand exactly why SCN seems to thrive when it’s dry, but we also know that nematodes grow best in the greenhouse under dry conditions. “
Conversely, the 2013 growing season began in Iowa with record rains, delaying soybean planting. “But by June 2,” Tylka says, “SCN females were reported on soybean roots in sandy soils just 26 days after planting. In a normal spring, we expect to see female nematodes 40 days after planting.
Very often, the only visible sign of soybean cyst nematode is an egg sac on soybean roots.
Criminal investigators often think like outlaws in order to catch them. Perhaps farmers should apply that strategy to stop the No. 1 soybean yield thief? Yes, soybean cyst nematode (SCN), a nearly microscopic organism, gets away with billions of soybean profit dollars each year. Thinking like a nematode can help arrest them, too.
What is SCN’s modus operandi? How does it thrive? What characteristics make it difficult to control? How does weather impact infestations? What management practices and growing conditions are conducive to reproduction?
Think differently for each field
Judd Hendrycks of North Mankato, Minn., began his SCN-management program 10 years ago when one field yielded 20% less than others. “SCN egg counts were higher than we wanted to see,” he says.
Hendrycks’ SCN-management program relies on rotating soybeans with non-host corn, trying SCN-resistant varieties and cleaning equipment between fields.
It’s been tough, the Nicollet County, Minn., farmer admits. “I’ve not seen a lot of change in yield. The resistant varieties have helped cut losses from 20% to 10%. I’ll continue to try new resistant varieties.”
Hendrycks planted a 30-acre test plot of Syngenta’s Clariva Complete Beans (new Syngenta biological nematicide awaiting approval, see sidebar) in early June. “If it’s effective and safe, I’ll probably add it to my program for 2014,” Hendrycks says.