U RESEARCHER: Deep freeze could kill emerald ash borer - FOX 10 News | fox10phoenix.com

U RESEARCHER: Deep freeze could kill emerald ash borer

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ST. PAUL, Minn. (KMSP) -

Anyone looking for a silver lining to the extreme subzero temperatures may get an answer when spring comes, because that will be the true test of whether invasive species have survived the harsh winter.

With weather warnings urging people to take precautions to avoid potentially deadly hypothermia, it's no secret that extreme cold can kill. Yet, when it comes to insects like the emerald ash bore, which has infested the trees at Lakewood Cemetery, the subzero temperatures may be Mother Nature's way of lending a hand in eliminating an ecological invader.

Death's cold embrace reaches out to even the smallest of invasive species, and no one is more pleased than Robert Venette, a research biologist with the U.S. Department of Agriculture whose research lab is on the University of Minnesota's St. Paul campus.

"I'm one of the few people who like weather like this, from the buggy side of things," he said.

Along with his research assistant, the two spent much of a historically frigid Monday carving larvae from the bark of ash trees, placing it in a Petri dish, and taking it outside to see how quickly it dies.

"It's around minus 20 that things get really interesting," Venette explained.

At -20 Fahrenheit, roughly half of the larvae will die. Once the temperature this -30, there's a 90 percent mortality rate. After two mild winters in a state where the emerald ash borer is now threatening to kill the state's 1 billion ash trees, Venette says one harsh winter could be a tipping point.

"The concern is that emerald ash borer might be moved into the central part of the state. That's where most of our ash resource is located," Venette said. "If emerald ash borer were to make it there and survive, it would be economically and ecologically devastating."

Although the epitaph for the emerald ash borer has not yet been written, Venette says he believes the cold could cause enough of a population loss to give people another opportunity to act.

"Communities have more time to find those infested trees and get them removed," he said.

Venette estimates the subzero temperatures may buy a delay of two to three years, but it is too early to tell whether a few plunges past -20 will be enough to evict the emerald ash borer.

The big chill can kill other bugs too. A University of Minnesota researcher recently discovered bed bugs face instant death at -22 -- but Entymology Professor Stephen Kells tells FOX 9 he would not recommend using outdoor temperatures to kill bed bugs even if it is possible.

Kells recently completed research on the topic and discovered that at 0 degrees Fahrenheit, it takes at least 72 hours to kill all stages of bed bugs. Exposure time drops to 24 hours at -11 degrees, but he cautions that factors like solar radiation, insulation, greenhouse effect (which occurs when items are wrapped in plastic), may complicate matters.

Wind chill is not a factor for bed bugs either, according to Kells. Although he acknowledges that need to address bed bugs living inside, he warns that people should never try to freeze bed bugs out because it could damage the structure of their home.

Yet, even the freezing temperatures farther north are no match for the moose ticks that carry parasites which are accused of killing off 70 percent of Minnesota's moose population. Wildlife Health Program Supervisor Michelle Castensen says that's because the ticks live on the warm host during the winter.

What would help kill the ticks is a long, cold winter that would linger until after when the ticks fall off the moose in April and start the next phase of their cycle. In other words: On the host they, survive the cold; off the host they may die if the freezing temperatures linger until May.

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