The discovery of the emerald ash borer at a campground near Emlenton, Venango County, as well as in five other counties, means the tiny green bug is now confirmed to have invaded 28 of Pennsylvania’s 67 counties.

The dark green borers were first detected in Michigan in 2002, and made their first Pennsylvania appearance in Cranberry Township in 2007.

The state Department of Agriculture said the borers also have been discovered in Jefferson, Bucks, Perry, Snyder and Franklin counties.

Emerald ash borers can kill an ash tree within three years of initial infestation by depositing larvae under the tree’s bark. The larvae emerge as adult beetles after one year, leaving a tiny D-shaped hole in the bark.

The beetles kill the trees by interrupting their circulatory systems, which is under the bark.