ELKHORN, Wis. (WSAU) – State officials said this afternoon that the emerald ash borer has been found in Walworth County for the first time.

The Agriculture Department said evidence of the tree-killing bug was found last week in a private woodlot at the Wisconsin-Illinois border. Then on Monday, an ash tree was spotted in downtown Lake Geneva with signs of being infested – and state officials confirmed the disease in that tree today.

The department's Mick Skwarok said the first case was discovered when Illinois was investigating a new line of infestations on its side of the border. He said the Lake Geneva case was not a surprise, since the city has many tourists and vacation homeowners from Illinois where the ash borer is more widespread.

Neighboring Rock County to the west will also be checked.

As a result of the new discoveries, Walworth County will be placed in a quarantine. That means ash trees and nursery stock cannot be moved from the county unless the state certifies them as being free of the emerald ash borer.

Similar quarantines exist in a dozen counties around Kenosha, Racine, Milwaukee, La Crosse, and Green Bay.

The ash borer was first discovered in 2008 north of Milwaukee. Its first appearance in the U-S was near Detroit a decade ago.