Invasive Species Awareness Week . HWA . Nova Scotia

It's Invasive Species Awareness Week in Canada (Feb 28 - Mar 4, 2022) and our focus will be on the hemlock woolly adelgid (HWA)

Many thanks to the three contributors who provide a past perspective, the current situation in Nova Scotia and a peek into the future.

And we have PRIZES!  We'll have a random draw for 10 very stylish boot brushes -- courtesy of the Nova Scotia Invasive Species Council -- to prepare you for the new realities of outdoor adventures.  To enter you just have to LIKE any of our Facebook or Instagram posts this week.  The random draw takes place on Friday March 4, 2022 at 5pm ADT and the winners will be contacted by Direct Message


Will Blozan is from North Carolina and the current President of Appalachian Arborists.  He started working with the US National Park Service in the Great Smoky Mountains National Park in 1993 where he mapped unlogged hemlock forests.  In 1996 he founded the Eastern Native Tree Society that documents exceptional trees in the eastern US.  This led into the Tsuga Search Project to find and measure outstanding hemlocks before they were taken out by the hemlock woolly adelgid.  

What was your early experience with HWA?

Altho HWA had been in the US since the 1950s, it did not show up where I worked in the Smoky Mountains until 2001/2002.  By 2005, most of the hemlock stands I worked on were infested and by 2007 they were virtually all dead.

Did all your hemlocks die?

We've had HWA for over 20 years and there still are live and viable trees. They don’t look good but they are still here. With a few exceptions, those surviving without pesticide treatment are in full sun. Most of the old-growth stands are long gone with maybe a few struggling to make it. I would say pretty confidently that there are no untreated old-growth stands of eastern hemlock left in the south.

How would you suggest dealing with HWA?

Define what is most important, develop a realistic management plan, secure funding and a way to implement it in a timely manner. Defining goals is important. You can’t save them all and there is no need to save every last seedling in a stand. Are you preserving water quality, habitat, viewshed, hazard tree reduction, seed sources? I think preserving a stellar stand of old-growth in as much of it’s entirety is a good thing so there is a reference point and example of what it is.

If you appreciate big trees, you may find the following article of interest -- 'The Last of the Giants' :


Jeff Ogden is the Provincial Forest Entomologist with the Nova Scotia Department of Natural Resources and Renewables

Where does HWA fit on the Provincial radar?

HWA is one of several invasive species we currently follow along with the emerald ash borer and beech leaf mining weevil. Currently HWA is receiving the bulk of our attention.

We are a key member of the Maritime HWA Working Group, providing input to the HWA Management Plan and lead the development of a Risk Assessment for HWA.  We rank HWA as high risk to our hemlock forest.  

Collaboration is very important with our many partners including the Canadian Food Inspection Agency (the regulators), the Canadian Forest Service (scientists),  Mersey Tobeatic Research Institute (active in HWA outreach), Medway Community Forest Coop (forest mgmt)  and others to monitor the spread of this pest through ground and aerial surveillance.

In 2018-20 NRR completed a study examining the biological development of the HWA. Our goal was to determine the HWA phenology in Nova Scotia and how its biological development may differ to that of other areas in eastern North America. This work is critical to numerous aspects of HWA monitoring, research, regulation, and management.  The results showed that we have longer periods of immature crawlers in the environment than other parts of eastern North America. This means our window for spread is greater. The crawler stage is the only mobile stage of the HWA and can be transported by wind, birds or artificially by us on forestry equipment or on-person. Our HWA also has a delayed spring egg laying compared to other populations period (ours start producing eggs in early April while in other areas it can be as early as Feb). We are currently analyzing the temperature data and comparing it to the HWA development to see if there are any correlations.

Current efforts to deal with HWA?

We monitor the spread through aerial surveys during our annual provincial overview survey.

We also collaborate with the Canadian Forest Service on a number of projects including one to develop monitoring tools and methods to increase our ability to detect HWA at low populations  A second project is exploring management options for the control of HWA including pesticide applications, silviculture and ultimately biocontrol. A third project is an annual health assessment of HWA populations throughout the infested areas and gauging winter mortality.

Community outreach is important as well.  We've developed a HWA rack card, a forest pest field guide and an invasive species poster.  We also consult with our First Nations and provide information to provincial stakeholders through social media posts and virtual and in-person presentations.

The ultimate goal is to develop effective monitoring tools for early detection of HWA and establish methods of control to not only slow the spread but overtime reduce the risk HWA poses to our hemlock forests.


Ecologist and long-time forest advocate Donna Crossland writes about hemlocks, their impact on wildlife and how landowners can ensure these giants continue to be with us ...

Nova Scotia's most graceful and largest evergreen -- eastern hemlock -- features dark green lacy boughs capable of forming dense canopies that shelter against cold rains, howling winds and deep snows.  

Hemlock groves can be regarded as "Mother Nature's barn" for protection against winter elements to white-tailed deer, barred owls, American marten, and other wildlife. 

Once infested, these hemlock sanctuaries will all be lost to hemlock woolly adelgid unless the trees undergo treatments to keep them alive over the next decade.  


We all have a role to play.  

Most important is to prevent HWA from infesting a new hemlock stand.  Acquire your firewood where you burn it to prevent the bug from accidentally getting a free ride to a new home.  

And when you are packing up after a hike/canoe/kayak, ensure your gear doesn't have any unwanted bugs.

And that's where your handy dandy boot brush comes in!  We have 10 to giveaway in a random draw selected from all the post LIKES this week. The draw takes place at 5pm ADT on Friday March 4, 2022.  Winners will be contacted by DM and announced in a Comment on this post.  Many thanks to the Nova Scotia Invasive Species Council for the awesome brushes!

Thank you for joining us this week ... and if you would like more information about specific things you can do to prevent the spread and deal with it once it's in your forest, please join us for our series during the week of March 21st.