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The battle against SCN continues

By Kriss Nelson - Farm News editor | Nov 2, 2020



There have been a growing number of pests showing resistance to varieties and pesticides and the Soybean Cyst Nematode (SCN) is no exception.

Greg Tylka, interim associate chair in plant pathology and microbiology at Iowa State University, who leads field trials on SCN said the widely available source of resistance is being broken down by SCN.

“Almost every resistant variety available to any Iowa farmer has resistant genes from the breeding line called PI88788,” he said.

The only other alternative Tylka said is Peking — but its availability is extremely limited.

“There are only four percent of all varieties that have Peking,” he said. “We have seen in our experiments Peking varieties yield up to 22 bushels and acre over PI88788 varieties, but the seed companies just aren’t bringing them to market as quickly as the PI88788 varieties.”

This issue is something farmers, Tylka said, need to be aware of.

“The resistance they almost have to buy, because it’s the only thing available, is becoming less and less effective every year,” he said. “The nematode is building up on it, just like weeds built up on glyphosate. That is the exact same principle. That underscores we have not won the battle.”

Especially after this year’s conditions.

“Soybean cyst nematode loves hot, dry soils and reproduces like crazy,” he said. “There is a way, way more egg number increases in hot, dry years than years with average rainfall. And what do we know about the growing season this year? It’s been hot and dry through a huge part of the state. I am really frightened to see what the numbers are going to be at the end of the season when we start to get our data in.”

Soil tests

Tylka advises soil samples be taken this fall to determine what those SCN numbers could be.

“Use soil cores – 20 soil cores for every 20 acres or so,” he said. “Most private soil test labs in Iowa process for soybean cyst nematode and then Iowa State has our own plant and insect diagnostic clinic that does it as well.”

An excellent source of information to utilize to learn more about SCN is a national education project called the SCN Coalition which can be found at: thescncoalition.com.

“There’s a ton of information on the website,” said Tylka. “There is a list of laboratories that process soil samples and all kinds of resources on that website.”

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