MADISON, Wis. -- Winter weather hasn't stopped crews from checking 44 Wisconsin counties for the emerald ash borer.

The Wisconsin Department of Agriculture spent the last month in Dane County cutting down ash trees that looked weak last summer.

Workers peeled back the bark to check for signs of infestation. During winter the larvae live inside the tree, making the beetle easier to find before it spreads, WISC-TV reported.

"If we were to do this same work in the summertime, those larvae will have changed into adults and emerged and the only thing left behind would be the galleries or the tunnels that they've created, but that's not enough to make a positive identification. We need to have a sample of the insect itself," said Mick Skwarok, plant, pest and disease specialist with the state Department of Agriculture.

So far, officials said that no emerald ash borers have been found in Wisconsin. To keep it that way, officials are asking that any firewood cut during winter be burned before spring.

Crews are moving on to survey Sauk County in the next couple of weeks, WISC-TV reported.