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 .  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  If it looks legit, it will be independently verified.

You find HWA, what's next?  

First -- please report any sightings to REVISED -- to   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

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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.