Insect Update: Will Extreme Cold Impact Insect Populations?

Air Date:
Heard On The Larry Meiller Show

Some reports say that our extreme cold this winter will impact the population of the Emerald Ash Borer in Wisconsin, while other researchers say don’t count on it. Larry Meiller finds out how cold and for how long it needs to be in order to reduce the presence of insect pests.

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  • Recent Cold Is Extreme But Not Enough To Kill Ash Borers

    One of the biggest insect issues in Wisconsin is the steady spread of the emerald ash borer. Nothing seems to be slowing down the spread of the ash borers much, and that’s a sad development for many of Wisconsin’s trees. But some wonder if the extreme cold this winter might put a dent in the insect population.

    Phil Pellitteri, an entomologist and head of the Univeristy of Wisconsin-Madison Insect Diagnostic Lab, said that the issue was even covered last week on NPR’s “Science Friday.”

    “The research would suggest that when you approach 30 (degrees) below, that you’re going to get very high mortality,” he said. “So, north of the Twin Cities, with some hope up in Superior because of the temperatures.”

    But Pellitteri added that it’s important to focus on actual temperatures, not the wind chill. At the lowest, southern Wisconsin was at about minus 18 degrees, he said.

    “So, I just don’t think we’re going to see a whole lot of positive effect,” he said.

    The Wisconsin Department of Natural Resources agrees with Pellitteri. In a recent article, Bill McNee, DNR forest health specialist, said that the ash borers “are somewhat protected beneath the tree bark and many of them will survive the recent cold temperatures. It will be a little warmer beneath the bark than the outdoor air temperature, and the wind chills do not affect them because they are sheltered.”

    In fact, the cold that most of the state has had might have helped the ash borers. Pellitteri explained that “one of the questions that’s unanswered is how well the parasites introduced to help control emerald ash borers are going to do in a winter like this.”

    Overall, Pellitteri said he thinks that even with colder than usual temperatures, the impact on most insects will be minimal.

    “Overall, so many insects are hiding in places that are not experiencing these kind of temperatures,” he said.

    Pellitteri said that insects for which Wisconsin is the northern edge of their range will be the most impacted by the cold.

    “I expect praying mantids to have a tough time getting through the winter,” he said.

Episode Credits

  • Larry Meiller Host
  • Judith Siers-Poisson Producer
  • Phil Pellitteri Guest