Emerald ash borer spreading faster in park

The spread of the emerald ash borer through Shenandoah National Park jumped significantly with new detections, park officials reported this week.

Rolf Gubler, the park’s forest pest manager, said, “We’re seeing more extensive pockets of infestation along the ridge tops.”

These ridge tops along Skyline Drive, Gubler said, seem to be “a movement corridor for [ash borer] through natural movement — perhaps they’re aided by wind.”

The park has now detected the ash borer in the counties of Rappahannock, Madison and Rockingham — areas farther south of where it had previously been spotted.

The park first detected ash borer in 2013, and the insects had advanced as far south as Luray last July, prior to this week’s reported detection.

As it has done since 2013, Gubler said the park will look to keep up its surveillance, trapping and preventive suppression measures, which include the strict regulation of firewood movement.

“We’ll focus more heavily on [the] central district and south district,” Gubler said, noting that they are still looking to strategically target sensitive areas of the park such as Big Meadows and Skyland.

This strategic suppression will also entail preventative treatments with pesticide.  Gubler said the park has a “very small treatment window” during the early spring months, when they attempt to treat between 1,000 to 1,100 trees.

In recent months, states around the county have taken to biocontrol measures including the purposeful introduction of a sting-less wasp species called spathius argil.

There have been reports of this measure working in some areas, such as Minnesota. However, Gubler said that the park is not looking into such measures at the moment.

“Those biocontrol measures that are in development right now are not as host-specific as we’d like,” Gubler said. “These parasitic wasps will go after native species as well, similar to emerald ash borer.”

Until those measures become more host specific, Gubler and the park will look to limit the damage ash borer may cause on its ash tree population up and down the valley.

Gubler said he thinks the spread of ash borer will be seen throughout the Shenandoah Valley as well as the Central and Southern Piedmont regions of the state in the next two to three years.

“More and more counties are going to light up as occupied by EAB,” Gubler said, which he added will lead to more mortality in ash trees along ridge tops and rivers.

He said they have already seen loss of green ash trees along rivers.

“You’re going to lose these riparian species … these are important trees to reduce erosion,” Gubler said.

The good news, Gubler said, is that Virginia has a bevy of seeding sources for trees to fill in the gaps when ash trees in both areas fall victim to the beetles.

“There’s gonna be other trees that come in and fill that niche,” Gubler said. “We’re hoping that we get good natives coming in, not destructive non-natives.”

Contact staff writer Kevin Green at 540-465-5137 ext. 155, or kgreen@nvdaily.com