PEORIA, Ill. — While Illinois enjoyed another record-setting year in soybean production in 2017, a renewed threat of soybean cyst nematode (SCN) damage is forcing farmers back to the drawing board to combat the familiar foe.
To encourage them to tackle the latest SCN threat, the SCN Coalition, a public-private partnership that helps farmers manage the plant disease, has reorganized after a 20-year hiatus. By “turning up the volume” on SCN resistance management, the reconstituted council aims to increase growers’ profit potential and realize higher yields, according to Greg Tylka, a nematologist at Iowa State University.
Tylka, who was a member of the original SCN Coalition, helped compile data from 25 variety trial experiments conducted by ISU that illustrate how as SCN reproduction increases on the PI 88788 breeding line, yields of resistant soybean varieties decrease as much as 14 bushels per acre.
“It’s much like the herbicide resistance problem developed,” he said. “After two decades of using the same source of SCN resistance, we’re seeing natural selection in action. The nematodes are adapting.” Farmers who do not test their fields for SCN should work it into their yearly crop management plan, Tylka explained.
Research is showing that because SCN is adapting and reproducing on resistant soybean varieties, yields are decreasing, according to the SCN Coalition. Tylka recommends planting only resistant soybean varieties that stop 90 percent of the SCN on a field from reproducing.
This is because researchers are discovering on some farms, 50 percent of nematodes studied have the ability to reproduce on the PI 88788 breeding line, which is present in about 95 percent of all SCN-resistant soybean varieties. The potential for crop damage and yield loss is magnified by the fact SCN can inhibit plant growth while causing little or no visible ill effect to a plant’s appearance.
The new SCN Coalition, which is funded by North Central Soybean Research Program (NCSRP), the United Soybean Board and coalition partners, is urging growers to “Take the Test; Beat the Pest” by testing their fields and knowing their SCN population numbers.
In addition, farmers should rotate resistant soybean varieties (even if it is still a PI 88788 source), rotate soybean crops with a non-host SCN crop and consider a seed treatment nematicide.
In Illinois, new research funded by the Illinois Soybean Assoc. (ISA) checkoff program is looking at cover crops, including winter wheat, as allies in the battle against SCN. Building on previous studies in Illinois and Kentucky, the study is showing promise for use of cover to reduce SCN egg populations.
The new study springs from earlier work done by former University of Illinois extension educator Mike Plumer, who documented SCN egg reductions following the use of grassy cover crops, and the University of Kentucky research proving the same for wheat stubble.
“These were limited trials, but if we can repeat these findings, we’ll help show that adding wheat or grass covers to the rotation before soybeans can provide another tool for managing SCN,” said Dan Davidson, ISA research technical coordinator.
The new study is being led by Jason Bond, professor of plant soil and agricultural systems at Southern Illinois University in Carbondale. “SCN remains the No. 1 cause of yield loss in soybeans, taking as much as 30 percent of soybean yield potential even if there are no visual symptoms,” he said.
The current study began last fall after collecting SCN samples and establishing baseline counts showing that more than half of the samples – 14 of 22 – had counts above the “cause for concern” threshold of more than 2,000 eggs per 100 cc of soil.
Like the SCN Coalition, the ISA also recommends farmers test their fields to confirm numbers, rotate to non-host crops between soybeans, consider a nematicide and rotate resistant varieties to help reduce SCN populations.
“Managing resistant populations will require multiple strategies, including resistant traits, rotation and chemical controls. ISA hopes this (cover crop) research gives growers another possible tool to consider for managing this pervasive pest,” said Davidson.
The NCSRP, a key sponsor of the first SCN Coalition and a driving force behind its March 9 relaunch at the 2018 Commodity Classic, agrees SCN is the top yield-robbing pest in soybeans. “There’s a clear need to raise awareness and re-elevate urgency among farmers and the soybean industry to understand SCN threats and the short- and long-term management strategies,” said Ed Anderson, executive director of the NCSRP.
Soybean producers can visit www.theSCNcoalition.com for more information about the SCN Coalition and for state and provincial-specific SCN management recommendations and resources from university experts.