Keeping the Legacy Alive

What is happening?

Biocontrol for Nova Scotia Hemlock Infested with Hemlock Woolly Adelgid

A Glimmer of Hope for Nova Scotia’s Majestic Hemlocks

The invasive Hemlock Woolly Adelgid (HWA) has been wreaking havoc on hemlocks since it was found in southwest Nova Scotia in 2017.  Researchers and volunteers have been working frantically to protect as many hemlocks as possible, primarily through inoculation of individual trees with approved pesticides. Now with the potential aid of certain biological pest controls, developed through years of research in the USA, hemlocks in Nova Scotia may soon see some reprieve.


Biological Control of HWA -update from CFS (NRCan) December 2023


As a long-term management strategy, researchers from Natural Resources Canada have been analyzing the potential role of biological control against HWA in Nova Scotia. A major factor in controlling an invasive species is whether or not any specialist predators exist in its environment. Without these predators, invasive species populations can increase without control. A three-year study in Nova Scotia confirmed that few, it any, predators attack HWA at level needed to stop their population increases. Consequently, efforts to source, ship, and release biological control agents was initiated. This project, founded on the significant peer-reviewed literature and research completed by scientists in the United States over twenty-plus years, led to the identification of a candidate beetle, Laricobius nigrinus.


This small, black beetle, which is about the size of a pinhead, is a specialist predator of HWA. It’s range includes British Columbia and other areas of the Pacific Northwest. Found nearly exclusively in and among HWA populations in this region, it can only complete development on HWA. This tight predator/prey relationship ensures that Laricobius nigrinus can follow HWA across the landscape, and establish itself in HWA populations. Additionally, this species has been released in the Northeastern United States for twenty-plus years with measurable positive impacts on hemlock trees at and around releases sites.


NRCan/ RNCan researchers are currently undertaking a research project to determine if a future program could be successful in Nova Scotia. In October 2023, releases of this beetle were completed in Shelburne, Queens, and Lunenburg Counties at vulnerable hemlock sites with recent HWA invasions. The goals of this project are to determine if Laricobius nigrinus can survive Nova Scotia’s winters, if it can establish in HWA populations, and if it can follow HWA populations across the landscape. The results of this research will provide the necessary information for the building of a long-term strategy for managing HWA in Nova Scotia and beyond.


Related Media Articles

Partner Programs

The Medway Community Forest Co-op is partnering with the province to launch a hemlock conservation program aimed at protecting Nova Scotia’s precious old growth hemlock forests from the invasive Hemlock Woolly Adelgid (HWA). MCFC will be forming “Strike Teams” to execute targeted pesticide application in old growth hemlock stands and protected wilderness areas across southwest Nova Scotia as well as establishing the “Hemlock Heroes” volunteer stewardship program to engage volunteers in assisting with HWA treatments. Visit Medway Community Forest to find out more. 


Kejimkujik National Park and National Historic Site (KNPNHS) is managing a Hemlock Woolly Adelgid (HWA) infestation using a combination of silvicultural and chemical control methods, which include the use of neonicotinoids. In 2021, a pilot project for the active management of Hemlock Woolly Adelgid was initiated. A detailed impact assessment was completed in the same year to assess the impacts of the project. A five-year project has been developed hat will increase Parks Canada’s understanding of HWA, enhance the resiliency of hemlock forests infested with HWA, slow the spread of HWA within and beyond Kejimkujik, and limit the impact of HWA on Kejimkujik’s old-growth forests.   

Find out more here.