HWA Detection & Prevention


Will these kids get to camp under hemlocks with their children?  

With over 35,000 acres of Nova Scotia's hemlock forest infested with the Hemlock killing bug HWA, we are at a critical point in the fight to save our hemlocks.

Right now (early May) is a very important time of the year.  Momma HWA has been busy making babies all winter.  And the cotton-like sacs where she lives are at their largest and most easily seen.

As the weather warms this month, her babies will come out of their protective home and start looking for a new source of food.  Called "crawlers", there can be MANY of them.  100s per sac.  

At the peak, scientists have counted 1,000s of crawlers falling from a single, infested tree.

How do you find HWA?

HWA are tiny -- about the size of a pencil dot.  

But they create a protective cotton-ball like sac around them that is visible and tells us that HWA is present.

The most common way to find the cotton balls is to grab a hemlock branch, flip it over and if infested, you will see the sacs where the needle meets the stem on the underside.

But what about branches higher up in the tree?  Here are a couple of options:

  • wind and ice storms will break off hemlock tips and branches scattering them on the ground where it is easy to inspect (this was a banner year for windfall where I live in Lunenburg County)
  • just before dark, shine a powerful light (greater than 2,000 lumens) with a focusable beam up into the branches.  The cotton balls will pop in the light
  • The pros use a pole saw that will reach up into the canopy where they can cut off branches and bring them down for inspection.

Please report any sightings (with a pic and location if possible) to hwa@nshemlock.ca

What do I do if I find it?

If you find HWA (or something that looks like it), please get a pic, the location and report it to hwa@nshemlock.ca

If this is a place where HWA has not been previously reported, someone from the Canadian Food Inspection Agency will visit the site to confirm the infestation.

VERY IMPORTANT : Early detection means there are more options for dealing with HWA.  Please let us know if you find any.

How do I prevent it from spreading?

HWA is most easily spread when the babies emerge from the cotton balls and start looking for food.  Called "crawlers", this happens from mid May thru until the end of August.  Over 1,000 can fall from an infested tree onto anything below.  And unfortunately, this is when lots of people are heading into the forest for serious R&R.  :-(

Crawlers are tiny -- about the size of a pencil dot.  So what can you do to prevent spreading them :
  • the picture above is the sign that will be going up in locations known to have a HWA infestation
  • please do not assume that the sign is in all locations where there is HWA!  It is found in all seven Western Counties and is moving eastward.  Best to be wary if you are in hemlocks
  • when you leave the forest, use a lint roller on your clothing and pets to remove any crawlers that may have fallen on you, your gear or your pets
  • avoid leaving an infested hemlock stand and visiting another hemlock forest (ie: awesome party weekend at Keji and then go directly to Victoria Park in Truro)
  • if you are headed for another hemlock site, please change your clothes.  5 minutes in a dryer will kill any crawlers
  • please do not remove any hemlock foliage from the forest
  • avoid parking your vehicle or ATV under hemlock trees

We all can help save our hemlocks by taking simple actions.

If you know what HWA looks like and report your sightings --> we can act early to contain it.

You can help minimize the spread if you take steps during HWA's active period from May to August -- use a lint roller to remove crawlers, change your clothing after visiting a hemlock forest, avoid parking under hemlocks, do not remove hemlock foliage --> we can slow the spread

And maybe, just maybe the children in the first picture will get to share the joy of camping in a hemlock forest with their children

HWA Detection/Information Session

Hemlock Woolly Adelgid (HWA) Detection Event 

Everyone is welcome to an information session in Kentville, Nova Scotia this Sunday May 1st.  

Details in the attached poster.

I hope to have an update after the event.

You & HWA

 You and HWA

This week is about specific actions you can take to help our hemlocks from the deadly hemlock woolly adelgid (HWA).

And we have PRIZES!!!  The very nice folk at the Kejimkujik National Park and Historic Site have provided five 2022 Adult passes.  If you would like to be entered into the draw, please send your email to giantsofnovascotia@gmail.com .  The winners will be randomly selected from all entries received by FRIDAY MARCH 25, 2022 at 5pm ADT. Your email address will only be used for the prize draw.

Can you tell which trees in the forest are hemlocks?

The picture above includes four, common evergreens found in our Acadian/Wabanaki forest that could be mistaken for hemlock.  You could confuse Balsam Fir branch tips with a hemlock but the trunks are very different.  Red Spruce are often found with hemlock and their branch tips are similar but the bark of the trunk is very different.  The same is true of White Pine -- they are often found with hemlocks and there trunks can look similar but the needles of a pine are very different from the needles of a hemlock!

The picture above shows common characteristics of our hemlocks, the Tsuga canadensis or "Canadian Hemlock".  The mature tree has dark brown deeply furrowed bark often with a reddish tinge.  It's a definite match if you can spot their very distinctive seed cones.  And in the spring, note the acid green growing tips.

DID YOU KNOW : iNaturalist and other apps are very helpful for identifying trees.  Take a picture of the trunk or needles or cones or all of them --> upload your pic(s) and the app will identify it for you.

Can you identify HWA?  

HWA spend the summer in their smallest growth form -- little black, tiny specs as small as a pencil dot.  Chances are that you won't see them without using a magnifying glass.

However, HWA secretes a waxy, white woolly substance that is visible.  Find it and you've found HWA.  The "cotton balls" are most visible in the spring but you can find them all year long.  The HWA "cotton balls" are usually found on the underside of a hemlock branch, close to where the needles meet the stem.

DID YOU KNOW : The "cotton balls" also shelter HWA's eggs laid in the spring. Opening one reveals the large female and her many eggs.

How do you find HWA?

Let's do a bit of sleuthing.  HWA exclusively feed on hemlocks.  The most common way it gets into a hemlock forest is by hitching a ride -- either on migrating birds or humans.

On birds, it probably gets started high in the canopy where the bird first lands.  And birds often fly along  waterways so it can be more common along rivers and lakes -- which is also where you will frequently find hemlocks.

For humans, the HWA and eggs will likely fall off infested trees onto their person, gear or wood and get transported to a new location.

DID YOU KNOW : Scientists have measured over 1,000 crawlers per day falling from an infested tree!  Yikes, that's a a lot! And if they were to land on you, your pooch or your vehicle, they are ready to ride to a new location.

The most common way to search for HWA is to grab a hemlock branch, flip it over and look at the outer ends of branches for cotton balls where the needles meet the stem.

How can you find HWA higher up in the tree? 

  • After an ice or winds storm, you will often find many hemlock tips and branches lying on the ground
  • Another way that works in late winter/early spring when the cotton balls are the most visible comes from our friends at the New York Hemlock Initiative -- shine a very bright light (>= 2000 lumens with a focusable beam) into the canopy just before dark.  HWA will pop in the light
  • Anytime a tree or branch comes down is an opportunity to do a quick search for HWA

Prevention, Prevention, Prevention.

Preventing HWA from getting to a new hemlock forest is key to slowing the spread.  On its own, HWA spreads very slowly.  Humans are very mobile and have the potential to relocate the bug 100s of miles in a single trip.  So what can you do?

  • Acquire your firewood where you burn it so you don't accidentally move wood infested with HWA (and a whole bunch of other bugs that affect other trees as well)

When you visit a site infested with HWA (or one that could be):

  • Avoid placing your gear or vehicle under or near hemlocks, particularly when it is most mobile and easily spread (May/Jun/Jul/Aug)
  • Before you leave the hemlock forest, run a lint roller or sticky tape over your clothing to remove any crawlers that may have fallen on you
  • The lint brush or sticky tape works on your pets too

It's a good practice to change your clothes after you leave a potentially infested area.  And please avoid immediately visiting an uninfested hemlock stand.

DID YOU KNOW : If you think you have found HWA in your favourite hemlock tree or forest, REVISED -- report it via email to hwa@nshemlock.ca  If it looks legit, it will be independently verified.

You find HWA, what's next?  

First -- please report any sightings to REVISED -- to hwa@nshemlock.ca   If this is a new sighting in a previously uninfested forest, it will be independently verified.

NEXT -- If you are a landowner or land manager, you have some choices.  HWA does not immediately kill your hemlocks but you have more options the earlier you start.  

The following is an example of what a homeowner might go thru:

  1. What's most important? I want to preserve the biggest hemlocks on my property around my buildings and protect the big ones along the waterfront that provide flood/erosion control
  2. What's your plan? At this time, the only way to save a hemlock infested with HWA is by injecting it with a pesticide.  I will do this for my six favourite hemlocks and I will hire someone to do it
  3. Funding? I understand there might be assistance available from the Nova Scotia government and I will check into it (PLEASE NOTE THAT AS OF APRIL 2022 THERE IS NO FUNDING)
  4. Timing? Pesticides work best when the tree crown is at least 65% intact (here is a tool to help you make that assessment) so I will assess state of my trees several times a year (spring and fall work well) and determine the priorities.  Old hemlocks should be treated as soon as HWA is in the area because the they respond slowly to chemical treatments

The following is an example of what a woodlot owner might go thru:

  1. What's most important? I cannot protect them all so I will focus on bigger hemlocks along the stream and one largely hemlock stand that is a magnet for wildlife
  2. What's your plan? I can sign out an injection kit (PLEASE NOTE THAT AS OF APRIL 2022 THERE ARE NO INJECTION KITS AVAILABLE) that will be available to landowners, write the pesticide operator exam (available on-line) and inject my own trees.  I will contact my neighbours for support and we can work together to inject hemlocks
  3. Funding? I understand there might be assistance available from the Nova Scotia government and I will check into it (PLEASE NOTE THAT AS OF APRIL 2022 THERE IS NO FUNDING)
  4. Timing?  Pesticides work best when the tree crown is at least 65% intact (here is a tool to help make that assessment) so I will assess state of my trees once or twice a year and determine the priorities  Old trees should be treated as soon as the HWA pest is near by because the chemical may take up to a year to begin working.

Everyone's situation is unique so your plan will reflect your priorities.

So what will likely happen if your hemlocks are infested and you decide to "let nature take its course".  Most of your hemlocks will likely die. Hemlock will likely be eliminated from your forest and your infestation will have an impact on the surrounding hemlocks.

5+ years from now there are promising control options involving bugs that feed exclusively on HWA.  Until then, it is very important to keep as many hemlocks alive and to prevent the spread.  And if you are dealing with an infestation, please consider all the options.

DID YOU KNOW : HWA is so deadly to our hemlocks because no natural predators exist and it multiplies like crazy.  A pesticide carefully applied to the individual tree can protect it for 4-7 years which gives us more time to find long-term solutions.  And our other friend in the fight?  HWA do not like cold weather (minus 20C to minus 25C) so maybe, just maybe the record cold temperatures we experienced this winter will set them back.

I hope this helped you.  More to follow as we learn how to deal with hemlock woolly adelgid.

And a few more resources about HWA

* * *

Many thanks to all the photographers for permission to use their images in this series.  A big shout out to Donna Crossland for her help with the TEXT and Will Blozan for his inspiration for how to deal with a HWA infestation.

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' : https://www.americanforests.org/magazine/article/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.