Mission: Hemlock woolly adelgid

Research Question

Where is the hemlock woolly adelgid? Where isn't it?

You're invited

Allison Kanoti, Forest Entomologist, Maine Forest Service, encourages everyone spending time with hemlocks within 20 miles of the coast to look for the hemlock woolly adelgid.

Mission steps


1. Print the species ID cards for hemlock trees and hemlock woolly adelgid (you may also want to have a balsam fir ID card handy since hemlock and balsam fir look quite similar).

2. Print an Upland Species Survey datasheet and hemlock woolly adlegid sampling protocol.

3. Find a hemlock tree

4. Following the protocol, look at the undersides of the twigs on 5 to 10 branches for the woolly masses and document evidence of what you found (or did not find).

5. Go to your My Vital Signs page (link at top right) to add your HWA "found" or "not found" observation

6. Check out the Change Over Time Analysis Mission to figure out how your observation fits and what it means

Why this Mission matters

The Maine Forest Service is actively surveying hemlock trees for hemlock woolly adelgid (HWA). The map above shows where HWA has been detected as of January 2012. The 2010 map shows towns were HWA was looked for an not found by scientists and interns as of November 2010.

2010 was a banner year (or not) for finding HWA. The warm winter allowed populations to build to detectable levels in new locations. To date it has been found as far east as Georgetown - more than 40 miles east of the site in Saco that held the record for easterly detections in 2009.

You can help Allison and the Maine Forest Service by looking at the hemlocks in your neighborhood and adding your observations to the Vital Signs database.

Identification tips from Allison

  1. HWA is only found on hemlock trees
  2. Hemlock trees look very similar to balsam fir trees
  3. Other things such as pitch and mealybugs may resemble HWA
  4. While you're looking at the twigs for HWA, keep an eye out on the undersides of the needles for elongate hemlock scale, a lesser known but equally damaging invasive insect. More information about both of these insects is provided by Maine Forest Service


Here is a cool resource to see county level observations of forest pests from across the country http://foresthealth.fs.usda.gov/portal/Flex/APE

This shows where some of those species that haven't been found in Maine yet, have been found. I'm not sure if it's totally up to date since I didn't see red pine scale found in Maine.


Students at Massabesic Middle School will be working to mobilize our community to sign up with Vital Signs and get out and search for Hemlock and HWA in our district towns. We know that our County is already quarantined because of HWA, but we will do what we can to get data to you on where else it might be. We will look for hemlock, let you know where we find it through Vital Signs submissions and if we find signs of HWA, we certainly will let you know this as well.

Here's an observation posted by the species expert that shows what HWA might look like this time of year. It's a helpful resource if you're out there looking in the late fall.


I have been studying hemlocks for almost the entire year now and I found that it's very easy to mistake other trees or species for Hemlocks. It's hard to find Hemlock Wooly Adelgid when you don't exactly what the characteristics of a Hemlock tree is.

Learn more about invasive forest pests, Wednesday, 6/6/2012

Check out this blog post for details: http://vitalsignsme.org/blog/bugs-trees

What are some of the signs of on setting wooly adelgid infestation?

The hardest part of this Field Mission can be finding a hemlock tree. You have to look closely at the needles and how they attach to tell hemlocks apart from balsam fir and other similar-looking species.

Before you go out, check out this great comparison tool from the Maine Forest Service: http://www.maine.gov/doc/mfs/hemlockID.htm