About two weeks ago, Alan Siewert was driving on Route 2 near the Heisley Road exit in Mentor when he saw some ash trees with defoliated crowns, said Mentor Tree Commission Chairman Cheryl Ray.

Siewert, a state urban forester, immediately knew what the lack of foliage meant – the Emerald Ash Borer had made it to Mentor.

The borer is an invasive species from Asia that came to this country via the port of Detroit. Since its arrival in 2003, it has gradually traveled east, killing ash trees along the way.

Its larva lives beneath the ash's bark, destroying the tree's xylem and phloem.

An ash tree usually dies three to five years after becoming infested.

"It girdles the tree and kills it, because no nutrients can get up or down," Ray said.

The borer was already in Cuyahoga and Geauga counties, but this is its first sighting in Lake County. Thus far, evidence of the insect and its larvae has only been spotted at the one location in Mentor.

Ray said those who have ash trees on their property can try to protect them with treatments. However, those treatments come with three caveats, she added: the treatments are expensive; they have to be done every year; and they do not guarantee the tree's safety.

However, Bob Martin, Mentor's director of parks, said some more reliable treatments have been used recently in Dublin, OH. He added that the city is looking into a treatment for about 50 ash trees in the City Hall complex.

No plans have been finalized, he said.

The Ohio Department of Natural Resources has not yet confirmed the borer's presence in Lake County. It is testing the DNA of specimens sent to it first.

But Ray and city officials have no doubt that they're dealing with the Emerald Ash Borer.

"Even without DNA testing, it's pretty obvious," Ray said.