An invasive insect is attacking the hemlock grove around where United Flight 93 crashed on Sept. 11, 2001, but officials hope a treatment plan will save the trees.
The Flight 93 National Memorial says in a Wednesday release that the hemlocks are infested with hemlock woolly adelgid, an invasive insect that can kill trees within a few years.
"I would say the stand is prettily heavily infested," Rick Turcotte, an entomologist with the U.S. Forest Service, told The Associated Press. "Trees are showing fairly significant impact," such as reduced growth, thinning of the crown, and off color needles.
United Flight 93 was traveling from Newark, N.J., to San Francisco when it was hijacked by four terrorists. The 33 passengers and seven crew members were killed when the plane crashed after passengers fought back against hijackers. The 9/11 Commission said the terrorists likely wanted to crash the plane into the White House or the U.S. Capitol.
The National Park Service refers to the meadow and hemlock grove where the plane crashed as the "sacred ground," because it's the final resting place for many of the remains of the passengers and crew.
Woolly adelgids, which are native to Asia, lay their eggs on the underside of hemlock branches, and the young insects feed on the sap of the trees, causing them to lose needles and die within five to 10 years. The insects appeared in Virginia in the 1950s and in southeastern Pennsylvania in 1969. They've been spreading north and west ever since.
Turcotte said the Forest Service is working with the National Park Service on a treatment plan for over 1,300 mature trees in the roughly 11-acre grove of hemlocks. They're trying chemicals and even releasing a species of beetles that eats the adelgids, which have no natural predators in the area.
In some other states and regions, adelgids have caused massive die-offs of hemlocks, and scientists still aren't sure if they'll be able to save the Flight 93 grove.
"In the big picture we don't really know if it's a losing battle," Turcotte said of area. "We're trying to maintain it in the condition it was in at the time of the crash."
The Flight 93 National Memorial is located in Shanksville, about 75 miles southeast of Pittsburgh. The memorial drew about 320,000 visitors last year.