Hanging On – Saving the Park’s Hemlock and Ash Trees

Keeping Shenandoah Wild

Project Title: Hanging On – Saving the Park’s Hemlock and Ash Trees

Project Purpose: to protect and preserve Hemlock and Ash trees from the serious threat from the invasive emerald ash borer (EAB) and hemlock woolly adelgid (HWA).

Project Goals:

  • to preserve a portion of the park’s eastern hemlocks for future restoration and until biological controls (Laricobius predatory beetles) can become established
  • to retain ash trees for visitor enjoyment, reduce threats to visitors from hazard tree formation, and to preserve a portion of the park’s ash tree communities until host-specific biological controls become available

Project Impact: In the past 25 years, HWA has killed 95% of Shenandoah’s hemlock trees, and without treatment, the EAB is likely to kill over a million ash trees in the park in the next 7-10 years. With proper funding to treat these trees, the park will conduct HWA and EAB suppression in targeted areas throughout the park. Approximately 2,200 hemlocks would be protected via HWA soil treatments. Approximately 140 ash trees in will be hand treated in 2022 (using emamectin benzoate/Mectinite® that is absorbed by the tree) and monitor treated trees. 

Project Funding: $33,000 

Project Progress: 

  • 2021
    • SNP Trust funded park biologists, working alongside Virginia Tech’s Hemlock Preservation Foundation, to purchase 500 predatory (biocontrol) beetles for release at a suitable hemlock site.
  • 2020
    • 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.
    • 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.
  • 2019
    • park 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.
    • 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.

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