Flight 93 National Memorial Begins Treatment Project to Save Hemlock Witness Trees Near Crash Site

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Date: November 6, 2013
Contact: Keith Newlin, (814) 931-1850

Stoystown, PA – NPS staff, partners and local contractors are hoping to save the remaining hemlock witness trees near the crash site at Flight 93 National Memorial. This project, which began this week, will suppress the spread of the hemlock woolly adelgid (HWA) insect populations and maintain the health of the existing hemlock stand. Flight 93 exploded into the trees when it crashed on September 11, 2001. The hemlock grove contains the remains of the passengers and crew.   Park staff discovered that the trees located within the hemlock grove are infested with HWA, a non-native, invasive insect that threatens the survival of the grove. The NPS and forest scientists from the United States Forest Service have embarked on a program to manage this threat and preserve the integrity of the hemlock grove. “We hope that these treatment methods will protect the hemlock trees and help us preserve the crash scene” said Superintendent Jeff Reinbold.

The presence of HWA can be identified by its egg sacs, which resemble small tufts of cotton clinging to the underside of hemlock branches. Hemlocks stricken by HWA frequently shift to a grayish-green appearance rather than the dark green of healthy hemlocks.

 Several different treatments methods are being used to maintain the aesthetic and ecological values of the area where the hemlock witness trees are growing. Over the next three years workers will treat 1,351 mature trees that have been selected for treatment, and will treat many seedlings/saplings as well.

The hemlock witness trees will be treated by a combination of soil-buried tablets, soil injection, low pressure tree injection, bark spray, and horticultural oil spray. Weather, soil conditions and insect activity will influence optimum treatment timing for the prescribed systemic insecticides.

 In eastern North America, HWA is a destructive pest that poses a major threat to the Eastern hemlock and the Carolina hemlock. The range of Eastern hemlock extends north of the current range of the adelgid, but there are fears that the adelgid could spread to infect these northern areas as well. Accidentally introduced to North America from Asia in 1924, HWA was first found in the eastern United States some decades later. In Pennsylvania, for example, the earliest record is from 1967. The pest has now been established in nineteen eastern states from Georgia to Maine, causing widespread mortality of hemlock trees. As of 2007, 50% of the geographic range of eastern hemlock has been impacted by HWA.

For more information on this project contact Keith Newlin, Deputy Superintendent, at 814-931-1850. Information about the hemlock grove can also be found on the Flight 93 National Memorial webpage at www.nps.gov/flni.

Last updated: October 27, 2017

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