Emerald ash borer invades national park

By Ryan Cornell

There’s a new fugitive hiding out in the Shenandoah National Park.

It’s metallic green in color. It’s about a half-inch long. It has wings. And it’s killed more than 50 million ash trees, including many throughout Virginia.

The culprit behind the destruction is a beetle known as the emerald ash borer.

After one of the insects was first discovered on Aug. 19 in a surveillance trap in the Dickey Ridge Picnic Grounds — the park has been monitoring for the beetle since 2009 — it’s become the focus of the park’s latest crackdown on invasive species.

The emerald ash borer lays its eggs on the bark of ash trees. The larvae that hatch from these eggs burrow under the bark and create feeding tunnels that cut off nutrients and water flow to the tree. Within three to five years of the infection, the tree typically dies.

According to emeraldashborer.info, a website curated by three universities and the USDA Forest Service, the ash borer is “now considered the most destructive forest pest ever seen in North America.”

The site lists several ways of identifying an ash tree infected by the pest. These include the thinning of the tree’s canopy, appearance of vertical fissures in the bark, increase in woodpecker activity on the tree and sprouting of large leaves from the roots and trunk.

Eric R. Day, an entomologist at the Virginia Tech Department of Entomology in Blacksburg, said the only way to prevent the beetles from infecting ash trees is to apply a systemic insecticide to the base of the tree.

If left untreated, he said the top of the tree will start to die off, followed by its branches. Once it’s dead, the tree poses a hazard of falling down.

The Shenandoah National Park, which has been treating its ash trees with pesticide since April, plans to treat 1,000 to 1,500 trees per year as its budgets permit. Ash trees account for 5 percent of the trees in the park.

“Because it’s out of the region,” Day said about the pest. “It has no predators and trees have no resistance against it.”

He said predatory wasps could eventually be used to permanently control the emerald ash borer as a bio-control method, but it’s still in the research stages and would take years to develop.

“These tiny little wasps, which don’t sting, go particularly after the ash borer,” he said. “One of the problems is that it works well with Asian species, but not so much with American species.”

Originally from Asia, the emerald ash borer is a non-native pest that was accidentally introduced to the U.S. in 2002. Day said the bug was first discovered in the U.S. near Detroit, but it’s unknown how it arrived in Virginia.

“There are so many ways these insects could have been moved here,” he said. “It probably came from infested nursery stock shipped from Michigan or though firewood being transferred.”

Shenandoah National Park regulations prohibit anyone from bringing firewood in from outside the park.

Today, the emerald ash borer has settled in pockets covering most of the state. Day said the insect is well established in Northern Virginia. It wasn’t until 2012 that the ash borer was detected in Warren County.

Day said people need to be more aware about what they might be unintentionally carrying.

“It’s one of those things that remind us why it’s important to have stuff checked at airports and others ports of entry,” he said.

The emerald ash borer has spread to 21 states and two Canadian provinces since it was introduced to the U.S.

People who suspect their ash trees might be infected by the insect are asked to call the Office of Plant Industry Services at the Virginia Department of Agriculture and Consumer Services at 1-804-786-3515.

Contact staff writer Ryan Cornell at 540-465-5137 ext. 164, or rcornell@nvdaily.com