The tree-killing emerald ash borer has officially landed in Kenosha.

Federal officials confirmed Wednesday that one was found in a survey trap on the city’s west side Monday.

The beetles consume the tissue underneath the bark of ash trees, which kills the trees. The beetles are estimated to have left about 50 million trees in the Midwest dead or dying.

The adult version of the bug is metallic green and measures about a half inch long and one-eighth inch wide. Potential signs of these beetles occupying trees include a dying tree crown, excessive sprouting of new branches, bark splitting, woodpeckers feeding on larvae, “D” shaped holes under the bark and “S” shaped patterns on the wood.

Mick Skwarok — plant, pest and disease specialist for the Wisconsin Department of Agriculture, Trade and Consumer Protection — said this was the first time an adult ash borer had been found in Kenosha.

A pair of ash tree saplings in Kenosha, which were imported from an ash borer-quarantined area of Illinois, were found to have ash borer larvae last fall. Skwarok said those larvae were found at a time of the year when there was no threat of escaping, and he strongly believed there was no connection to the beetle that was found Monday.

“That threat was mitigated beyond a shadow of a doubt,” Skwarok said.

Kenosha has been guarding against these beetles as populations in Illinois grew, and 76 traps were set up in Kenosha County to gauge the bugs’ presence.

Skwarok said a number of factors could have led to this week’s appearance.

“If you look south to Illinois, there are a lot of infested trees,” he said. “It’s not out of the realm of possibility that it flew up from there. Racine, Rock and Kenosha counties have been on the lookout for some time, given what is going on in Illinois.”

Emerald ash borer populations are increasing in Wisconsin. The bug has also been found in Brown, Crawford, Ozaukee, Vernon and Washington counties.

“Once we made our initial discovery, successive years reveal more and more signs of infestation,” Skwarok said. “There is more public awareness and calls reporting suspicious-looking ash trees. The infestations have another year to get worse, and with each passing year the infestations become a little more obvious.”

There are about 8,000 traps set up around Wisconsin to identify ash borer locations.

The discovery means that Kenosha is a pending ash borer quarantine area. That designation means that potential ash borer breeding grounds — such as hardwood firewood, timber and logs — cannot be taken from Kenosha County to another county. Skwarok said the quarantine status is likely to take a few days to officially go into effect.

The next steps in dealing with the presence of ash borers will have to be determined by local parks and forest departments, Skwarok said.

“We will be working with them and federal agencies to come up with a plan,” Skwarok said. “Our first priority is to wrap up our survey program that is currently under way and start talking about what we will be doing this fall.”

Skwarok said potentially infected trees can sometimes be easier to find in the fall and winter.