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Experts say most bugs that plague Indiana likely survived cold winter

Tuesday, March 18, 2014 - 4:46 pm

LOGANSPORT — After biologists and weather forecasters hoped this year's bitterly cold winter would kill off some of the state's most pesky insects, state bug experts say that probably didn't happen.

Some residents hunkering down in January and February hoped the bitterly cold temperatures would deal a fatal blow to some of the area's emerald ash borer population. The invasive beetle has put native ash trees in danger of extinction.

But it just wasn't cold enough, state entomologists explained.

Research on how well ash borer larvae survive the cold has shown that about a third of larvae population studied will die if the temperature surrounding them dips to negative 10 degrees. However, the air temperature recorded somewhere isn't necessarily what the larvae actually experience, nursery inspector Eric Bitner said.

"Larvae of (emerald ash borer) spend the winter under the bark and some of them close to the ground which provides insulation," Bitner said, or remain insulated by snow cover. "I believe that the cold will do some good in preventing EAB populations from building up more quickly but not significantly."

Other bugs probably weren't harmed much, either, according to the state health department's bug expert.

"Hard winters don't have nearly the bad effect on mosquitoes and ticks and things like that that people might think they would," said Bryan Price, senior medical entomologist with the Indiana State Department of Health.

Pesky bugs — especially the mosquitoes that carry the West Nile Virus, which causes flu-like symptoms in people — can withstand a wide variety of weather conditions, Price said. And they're hibernating through the winter in protected spots, like drainage culverts or inside barns, where it's a bit warmer than out in the elements.

One scenario that might reduce pest populations, at least temporarily, would be if the weather warmed up enough to bring the insects out of hibernation, then got cold again.

"That will kill off some of those mosquitoes for sure. But then again, they can sense this," Price said, and seek shelter.

And any reduction would only be temporary, he added. "The survivors would then start laying their eggs again and the process would just continue on."

Ticks probably weren't stopped by the cold weather, DNR entomologist Philip Marshall said. "There will be some reductions," he said, but bitter cold is "not the panacea."

"A lot of times what you need is more of a sudden change in a short period of time," he added. "That helps to do more damage to insects, and even us, than a gradual change."

The Royal Center native believes ticks were protected beneath the heavy snowfall that occurred.

"I think they were underneath the snow, so they were insulated. Snow will protect them. That's why we make igloos," Marshall said. "The other analogy is — if the weather can kill off all the insects like everybody wants, it could do the same thing to us."

The biggest effect of a harsh winter, Price said, is probably just to delay the start of the mosquito season.

He pleaded with homeowners to watch for standing water once all the snow melts and to remove potential mosquito breeding grounds wherever possible. Steps like rinsing birdbaths once a week and flushing out kiddie pools and flowerpots would go a long way to keeping mosquitoes from proliferating, he said.

Information on the Purdue Extension's emerald ash borer website indicates ash trees that are still healthy can be protected from the emerald ash borer, too, by using a soil drench or bringing in a tree care professional.

"Indiana has seen winters this cold before, and we'll see them again," Price said. "Insects, unfortunately, are well-adapted to that. There's not much Mother Nature can do to help, I'm afraid."