Park taking comments for adelgid predator beetle

Shenandoah National Park may be turning to a new ally — predatory beetles — in order to combat the destructive hemlock woolly adelgid.

The park will be taking public comments through Oct. 15 on its plan to release predatory beetle species at four locations within its boundaries.

Rolf Gubler, the park’s forest pest manager, said, “We’re real comfortable with this biocontrol … this (beetle) in particular is very host-specific, so it’s needing the (adelgid) to complete its lifecycle.”

The beetle the park may be releasing is called Laricobius osakensis – which originates from Osaka, Japan, and is the adelgid’s natural predator.

Other public parks including the Great Smoky Mountains and the George Washington National Forest have employed the use of predatory biocontrol beetles on woolly adelgid.

Shenandoah National Park officials hope that the beetle’s presence will allow the hemlock tree populations to recover and recoup from losing roughly 95 percent of its numbers from the woolly adelgid.

Since the woolly adelgid is an invasive species with no natural checks or predators, the park has had to resort to treating high-density hemlocks with subsurface pesticides.

However, Gubler said that they have been looking at employing a biocontrol measure like this for the past two years, but have struggled to find fitting locations to introduce the beetles because of the treatments.

“Many of our sites that have healthy hemlocks are also treated, so you can’t use those for release sites,” Gubler said, noting that the beetles would require untreated sites with healthy hemlock trees in order to breed.

Gubler said that this has proven difficult given the amount of time that the invasive adelgid has spent in the park.

In addition, the park might find it difficult to release the beetles at the four potential sites selected if the adelgid population is down from this past winter’s freezing.

“We’re going to have to go out in the next two-to-four weeks and look at these release sites … and make sure that these sites have enough (adelgid),” Gubler said.

While there is not a specific number he could quote, Gubler said park officials will “assess the foliage of the hemlocks” for mass presence of woolly adelgid.

If the park is able to establish pockets of the beetles as a counter balance, Gubler indicated that he expects woolly adelgid numbers to shrink slightly.

“If there are ample populations of (adelgid), then this thing is going to thrive,” Gubler said.

He cautioned that park visitors should temper expectations on how successful the beetles could be in the immediate future.

“These beetles take a long time to build populations to get to a point where they are successful,” Gubler said. “It could take five, 10 or more years in some areas … park-wide it could take even longer.”

He added, “It’s a step in the right direction in terms of trying to get ourselves off of the chemical control cycle.

“It’s an effective, efficient means, but we don’t want to be on a systemic pesticide cycle forever. Eventually, we wanna turn over to these predatory beetles.”

Gubler said they are aiming at releasing the adelgid in early November once the comment period is over. Comments on the park’s plan can be submitted at:

Contact staff writer Kevin Green at 540-465-5137 ext. 155, or

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