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Knowing SCN Numbers to Evaluate Best Sources of Resistance

SCN Coalition Reboots to Battle Resistance-media-2
Dr. Greg Tylka, SCN Coalition nematologist

Soybean cyst nematode (SCN) is the most damaging soybean pathogen in the country. Most farmers don’t know they have a problem until it’s too late. It’s estimated to cost farmers more than $1 billion in lost yields.

According to Dr. Greg Tylka, nematologist with the SCN Coalition, the way growers manage SCN has changed.

“It used to be easy to manage—you simply bought a resistant soybean, you grew it, and everything was peachy keen,” he said. “You rotate with corn and everything was just fine. That was true for a couple of decades. There’s a problem brewing all those decades, and that was that almost every resistant variety a farmer could ever grow, had the same set of resistance genes.”

Just like using the same active ingredient in an herbicide for decades, nematode resistance genes are now resistant to the resistance.

“That problem isn’t widely known either,” said Tylka. “Another one of the SCN Coalition’s main messages is that resistance isn’t working as well, and you need to be aware of what your numbers are and use every possible tool to manage soybean cyst nematode.”

The most common type of resistance is called PI 88788. The other type of resistance is called Peking. In a 2019 field experiment, Tylka found that planting the Peking resistance could save up to $200 an acre.

“We had an experiment with 68 varieties that had PI 88788 resistance—they averaged 50 bushels per acre,” said Tylka. “The two Peking varieties averaged 72 bushels per acre—that’s a 22-bushel yield difference. Pekings always had a bad rap of having low yield potential compared to PI88788. SCN is dragging down the yields of 88788 such that Peking is the better-yielding source of resistance.”

There will soon be a third source of resistance with a new commercial variety from Syngenta and Northrup King in 2021.

“PI 89772 is the source of resistance,” said Tylka. “It’ll be available in a Golden Harvest variety branded soybean and a Northrup King branded soybean. It’s the same genetics in those two variety names.”

This new source of resistance will a positive thing for soybean producers. However, the need for SCN resistance is still greater than the supply. For more information, visit TheSCNCoalition.com.