Hemlock woolly adelgid control project annual report 2012: New River Gorge National River, Gauley River National Recreation Area, and Bluestone National Scenic River
Strickler LK. 2014. Hemlock woolly adelgid control project annual report 2012: New River Gorge National River, Gauley River National Recreation Area, and Bluestone National Scenic River. Natural Resource Report. NPS/NERI/NRR—2014/818. National Park Service. Fort Collins, Colorado
Eastern hemlock (Tsuga canadensis) forests are valued for their ecological attributes, aesthetic worth, and recreational uses. Since the 1950s, these long-lived trees have been under attack in the eastern United States from an exotic invasive insect, the hemlock woolly adelgid (HWA). At New River Gorge National River (NERI), Gauley River National Recreation Area (GARI), and Bluestone National Scenic River (BLUE), HWA started infesting stands of hemlocks in 2002, 2007, and 2000 respectively. With a foresight for the inevitable infestation of HWA, 36 long term monitoring plots were set up across 3 soil moisture gradients (hydric, mesic, xeric) in 1998 before HWA was present in any of the parks. The xeric plots seem to be the most affected by HWA with the highest mortality and least healthy crown vigor. Mesic and hydric plots both show overall negative crown vigor and positive mortality trends. Other supportive evidence for the devastation of HWA on hemlock comes from treatment monitoring in three different areas. The amount of HWA found on an untreated hemlock is inversely proportionate to the crown vigor rating; as the rating increases, or becomes less vigorous, the density of HWA increases. Treated trees do not show the same trend as untreated trees and there is a statistical difference (α=0.05) at two locations. This suggests that the efficacy of the pesticide treatments is high, which increases or stabilizes the health of hemlocks in highly infested areas. Throughout the three parks, a total of 12,094 trees have been treated with pesticides. Because pesticide treatment is only a temporary solution, three species of HWA predatory beetles have also been released: Laricobius nigrinus, Sasajiscymnus tsugae, and Sycmnus sinuanodulus. Ecologists are hopeful that predatory beetles will suppress HWA populations to levels where the majestic hemlock forest is preserved into the future.
- Type
- Published Report
- Authors
- Strickler, Layne
- Date of Issue
- 2014-06
- Publisher
- National Park Service
- Units
- BLUE , ERMN , GARI , NERI , NRSS
- Keywords
- Hemlock Woolly Adelgid, hemlocks, HWA, Tsuga