The park is under serious threat from invasive insects. The emerald ash borer (EAB) and hemlock woolly adelgid (HWA) threaten to kill over a million trees in the park in the next 10-15 years.
Since 2018 SNP Trust has supported HWA soil treatments on hemlock trees and EAB treatments on ash trees. Approximately 5000 hemlocks and 180 ash trees have been treated. The goal of this project is to preserve a portion of the park’s eastern hemlocks for future restoration and to retain some ash trees for visitor enjoyment, reduce threats to visitors from hazard tree formation, and to preserve a portion of both trees until host-specific biological controls become available.
In the spring of 2021 SNP Trust will fund park biologists, working alongside Virginia Tech’s Hemlock Preservation Foundation, to purchase 500 predatory (biocontrol) beetles for release at a suitable hemlock site.
These projects will prevent the complete loss of ash and hemlock trees and forest and provide surveillance monitoring to improve future forest pest management response. The projects will mitigate ecological and aesthetic degradation of natural forest systems in treated areas, assuring that some park forests will continue to support the plants, animals, and opportunities integral to providing a rewarding visitor experience.
In 2020 (10/1/19-6/30/20), staff treated 1579 hemlocks to suppress HWA in select locations using soil treatments (w/Zenith® 75 WSP – 75% imidacloprid and CoreTect tablets) to a fairly large genetic pool. These areas included Big Meadows, the North Fork of the Thornton River and the Sag/Fork Mt. These hemlock sites were mapped at 384 gross acres.
In 2020, (6/8-6/30), staff treated 59 ash trees with stem injections of TREE-age/Arbormectin (active ingredient emamectin benzoate) using a Tree IV system (Quick Connect TM ). Developed Area ash trees that had the
potential to become hazard trees were targeted for treatment. These areas included Mathews Arm Campground, Elkwallow Area, Panorama, Dickey Ridge Picnic Area, Camp Hoover, Meadow Spring Parking, Pinnacles
Research Lab and near several backcountry huts. Treated trees were inventoried and mapped. Additionally, staff worked with a number of volunteers to accomplish this work. These included two ACE Interns and three previously trained volunteers.
In November 2019, staff worked with Virginia Tech staff to release 500 Laricobius nigrinus predatory beetles at the Meadow Run release site. These biocontrol beetles will eventually help to suppress HWA populations in
these areas.
In October/November 2019, park staff monitored HWA populations at three potential Laricobius release sites (Ivy Creek, Meadow Run, and North Fork of the Thornton River).
In November, staff monitored Laricobius osakensis populations at two release sites using beat sheet sampling.
Three adult L. osakensis were recovered at Madison Run and none were recovered at the South Fork of the Moormans site.
Three noteworthy points
1. In HWA treatment areas, hemlock crown health remained stable or improved at most locations in 2020.
At the Thornton River site, hemlock health declined slightly due to the longer treatment interval (12 years since last treatment).
2. Staff can achieve eight or more years of treatment longevity from imidacloprid soil treatments now that HWA populations are somewhat suppressed/dispersed throughout the park.
3. Park staff coordinated with Dr. Scott Salom at VA Tech in an effort to expand our Laricobius osakensis/nigrinus release efforts to occur on a roughly yearly basis (contingent on suitable release site conditions). We propose to do this in FY 2021, by having the SNP Trust work directly with Virginia Tech to fund approximately 500 Laricobius beetles for release in Shenandoah. Laricobius beetles are host-specific bio-controls used to suppress HWA in areas that are not treated with imidacloprid.