PENNSYLVANIA — A predatory beetle is a valuable tool to preserve the threatened hemlock trees within the Sacred Ground at the Flight 93 National Memorial, which commemorates lives lost in southwestern Pennsylvania on 9/11.

Eastern hemlock (Tsuga canadensis) is a slow-growing tree that may live for 800 years or more. But the hemlock woolly adelgid, an invasive insect that feeds on the hemlock’s stored carbohydrates, has threatened hemlock populations across the eastern U.S. In 2012, the USDA Forest Service and the National Park Service, which administers the Flight 93 National Memorial, developed a management plan to ensure the continued presence of the hemlock trees, a primary resource of the memorial that bore part of United Flight 93’s crash impact, there into the foreseeable future.

Personnel from the Forest Service Eastern Region Forest Health Protection Program, Maryland Department of Agriculture, Pennsylvania Department of Conservation and Natural Resources Bureau of Forestry and National Park Service all contributed to this biocontrol element of the management plan. The team met at Rocky Gap State Park in Maryland to collect the predatory beetles (Laricobius nigrinus), which are native to the West Coast and serve as a promising biocontrol agent for hemlock woolly adelgid. The beetles became established throughout Rocky Gap State Park after 1,200 were released there in 2004.

A total of 772 beetles were collected and transported by Tim Tomon, DCNR, and Danielle Kelley, a forest health technician for the Forest Service’s Eastern Region. Brenda Wasler, the natural resource manager for National Parks of Western Pennsylvania, met them at the Flight 93 memorial to release the beetles in two locations. The first release was on hemlock trees adjacent to the site. The second set was released in the “witness trees,” a large stand of mature hemlock trees near the footprint of the crash.

The goal is for the released predatory beetles to provide a consistent level of protection to the hemlock trees at the Flight 93 memorial. Once established there, these beetles could maintain the health of hemlock trees indefinitely, unlike insecticides that need continued application to remain effective. Protection of the witness trees will ensure a living memorial for generations.

The Forest Service will continue its shared commitment of hemlock preservation with the National Park Service by protecting hemlock trees within the ‘witness grove’ as a vital component of the Flight 93 National Memorial.

The National Park Service created a video (below) on this collaborative effort.