Farmers should consider SCN resistance during seed selection

Farmers have a lot to consider when it comes selecting their soybean seeds for 2021, ranging from yield potential to multiple genetic options for weed control programs.

But one factor that should not get lost in the shuffle revolves around soybean cyst nematode (SCN) resistance.

SCN remains the most destructive pathogen of soybeans with annual yield losses estimated at more than $1 billion nationwide.

In response, the SCN Coalition – a public/checkoff/private partnership formed to increase the number of farmers actively managing SCN – urges farmers to talk to a seed representative or crop consultant to determine if they’re using an effective source of SCN resistance and rotating sources of resistance.

Most SCN-resistant varieties contain the PI 88788 source of resistance, but the nematode is dragging down the yields of these varieties in many soybean fields, according to Greg Tylka, Iowa State University nematologist.

“Not every SCN-resistant variety with PI 88788 is equally good in terms of nematode control,” Tylka said. “Still, in many experiments, we see the Peking source of resistance outyielding the best PI 88788 varieties.

“And for 2021, soybean growers will have a third source of resistance sold by Syngenta under the Golden Harvest and NK Seeds brands,” he noted. “That source of resistance is PI 89772.”

Farmers should discuss the different options with their seed representative or agronomist to develop a plan to manage SCN. They should test their soils for SCN to enhance this strategy.

“Growers need to ask what source of SCN resistance they are using and make sure they rotate to another source of resistance to keep the nematode guessing,” said Kaitlyn Bissonnette, University of Missouri plant pathologist.

“Studies show after using PI 88788 for decades, it isn’t as effective as it once was in many fields,” she noted. “That’s why growers need to more actively manage SCN and take the first step and test their soil for SCN, if they haven’t already done so, to know which field are problematic.”

In heavily infested fields, SCN can cause soy yield losses of more than 30%, and in some sandy soils, nearly total loss in drought years.

SCN was confirmed in every county in Illinois and Iowa and all but two counties in Indiana as of 2019.