Farmers, scientists disagree on impact of wild winter on pests, diseases, fields

Farmers, scientists disagree on impact of wild winter on pests, diseases, fields

With temperatures reaching as low as 17 below during the polar vortex's recent visit, some farmers are hoping that was enough to kill off some of the pests and fungi they have to fight during the growing season.

"There's different opinions on that. A lot of the hard scientists say, 'Nah, it doesn't have any impact,'" said Lin Warfel, who farms near Tolono. But if you ask farmers, there's "agreement that it does impact it."

He's right that scientists are in agreement.

Nathan Kleczewski, a University of Illinois assistant professor who studies plant diseases, said pathogens have adapted to survive harsh winters.

"They're used to having winters and deep freezes. A lot of them are going to produce overwintering structures so that they are resistant to cold temperatures," he said. "The majority of the pathogens we deal with in field crops aren't likely to be significantly influenced by cold temperatures."

And Nick Seiter, an assistant UI professor who studies crop insects, said the insects that stick around should also have been able to survive the polar vortex.

"Most of the pests we have in Illinois are well-adapted to the temperatures. They're hunkered down for the winter," he said. "For a quick cold snap like that, even though it was really cold, I probably would not expect that to have much of an impact."

While people above ground have to deal with the wind chill, insects are "either buried in leaf residue or burrowed in the soil, so they avoid all that."

While the Illinois State Water Survey recorded air temperatures of 17 below, just 2 inches below the surface, the soil only fell to 16 degrees above zero on Jan. 31.

Four inches below, the soil only got as cold as 24 degrees, and 8 inches below, it only got to 31 degrees.

"The top several inches of soil will freeze, but below that, if you get deep enough, it stays fairly warm," Seiter said. "That's where those insects are going."

Besides that, insects enter diapause during the winter, Seiter said, an inactive stage somewhat like hibernation.

"It prevents them from becoming active during the winter, and it takes prolonged warmer temperatures like we experience in the spring for those to become active again," he said.

If there's any impact from the cold weather, it could be on insects that head south for the winter.

"The further south we have cold temperatures, the longer it takes for them to make their way up here," Seiter said.

Another way winter could affect this year's crop is if the temperature keeps fluctuating between freezing and not, as it has lately.

"This cold, warm, cold warm fluctuation we've seen the last couple months, that could maybe influence things more so," Kleczewski said.

He compared it to a tree that starts to bud too early during a warm spell.

"They put their buds out, then it freezes and they lose all those," he said. "A fungus might come out of dormancy and might not be in a stage to survive when there's a sudden shift in temperature, especially when it happens repeatedly."

Seiter said that could happen to insects, too.

"We're not there yet, but it's a situation that can occur and that can have an impact," he said.

Howard Brown, Illini FS' manager of nutrient stewardship, agreed.

"It most likely won't affect the pathogens because they're in the resting stage, so it has to stay really cold for really long," he said.

And he said the genetically modified crops farmers use now can handle most of the major pests.

"We're doing a pretty good job of controlling them with transgenic crops," Brown said.

Other farmers said they're not too concerned about the cold spell.

"Just being that couple of days, I don't think it had much of an impact," said Mike Briggs, president of the Champaign County Farm Bureau board.

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