Insect damage recently found on some area ash trees wasn't caused by the emerald ash borer, an invasive insect that's destroyed tens of millions of trees since its discovery a decade ago in Michigan.

The Pennsylvania Department of Agriculture has identified the culprits as the bark beetle and, mostly likely, the redheaded ash borer, both native beetles, according to Tim Elkner of the Lancaster County Penn State Cooperative Extension.

All three beetles feed on ash trees, with larvae boring into the tree or under the bark. Damage can look similar, which caught the eye of an arborist who alerted state officials to the possibility of the emerald ash borer's presence on May 21.

Borer damage includes dead leaves on the tree's canopy and new shoots branching out from limbs below dead areas, a process called epicormic sprouting. Bark beetle larvae leave bore patterns under the bark that resemble those of the emerald ash borer.

"There are similar symptoms. And I think that's the important thing, similarity," Elkner said Wednesday. "I think it's important for folks to get an accurate diagnosis."

A key sign of the emerald ash borer is a "D"-shaped exit hole made by the adult, and that was missing in the suspect trees. Native borers make round holes.

The suspect trees are along Wilson Avenue near the Wheatland Shopping Center in East Hempfield Township, and one tree is in the School Lane Hills area.

In both cases, Elkner said, the trees are nearing the end of their lives.

The tree in the School Lane Hills area is 2 feet in diameter.

"This tree has probably just been dying over time," he said, making it susceptible to the redheaded ash borer.

The trees by the shopping center also are in a hard environment — growing near pavement and being trimmed for power lines — making them easy targets for bark borers, he said.

In attacking the weakened trees, the native beetles "were just doing what Mother Nature programs them to do," Elkner said.

Elkner advised ash tree owners to "be vigilant but not overly concerned" about the emerald ash borer, which has yet to be confirmed in the county. But it may just be a matter of time before it arrives.

Instead of just targeting weakened trees, the emerald ash borer also feasts on healthy ash trees, Elkner said.

The half-inch metallic green insect is native to Asia and is believed to have arrived in the Detroit area in wood packaging materials. Since then it has spread to more than a dozen states.

It was first spotted in western Pennsylvania in 2007 and gradually has moved east. It's been identified in a third of Pennsylvania's counties, most recently Bucks, in March.

"It can pop up anytime on its own," Elkner said. "It moves about half a mile a year on its own, so its natural dispersal is fairly slow as far as insects go."

The emerald ash borer's spread has been aided by humans moving ash, including firewood, which is how Elkner figures it arrived in Bucks County.

Information about the emerald ash borer can be found at http://ento.psu.edu/extensi...

dnephin@lnpnews.com