Hemlock Woolly Adelgid Initiative

Early Detection Saves Trees

Overview

Hemlock Woolly Adelgid (HWA) is an invasive insect that infests eastern hemlock trees. The adelgid feeds at the base of the needle, consuming a hemlock’s stored nutrients, slowly sucking the life from the tree. Left untreated eastern hemlock trees become sickly, turn gray, and will succumb to the adelgid in 4-10 years. HWA has been spreading up the coast of Western Michigan for several years now, with confirmed infestations in 7 counties. Early detection of this forest pest is critical, the sooner an infestation is found the sooner treatments to save trees can begin. As a CISMA, we have grant funding from the Michigan Invasive Species Grant Program and the U.S. Forest Service to offer free surveys for HWA in high-risk areas. Please feel free to contact us with any questions you have about Hemlock Woolly Adelgid surveys and treatment information.

Hemlock Survey Consent

Winter Surveys

HWA surveys are conducted in the winter for several reasons. First, the adelgids are most visible in the winter when cooler temperatures trigger feeding activity. As the adelgids feed they secrete a white, waxy substance that forms a round ovisac around them making the tiny insects easier to see. Additionally, the insects are only mobile in the spring and summer. Winter surveys ensure we're not inadvertently spread HWA from one site to another.

If you live or own property within the orange area on the map you qualify for a free HWA survey from us. Residents outside of this area of focus are still welcome to sign up, and will be notified if there is additional time at the end of the season to survey their property. The orange area was selected because it's the most likely place for HWA to exist within our region.

What to expect from an HWA survey

Learn more about Hemlock Woolly Adelgid

Why are Eastern Hemlock trees important?

Frequently asked questions

Learn about HWA

Hemlock Woolly Adelgid (HWA) is native to Japan where it feeds on Asian species of hemlock and spruce trees. In its native range HWA is not an issue because Asian hemlock species are fairly resistant to HWA and predatory insects are accustomed to feeding on the adelgids. In North America the Eastern Hemlock tree (Tsuga canadensis) is highly susceptible to HWA attacks, while spruce tree species are not.

Identification

HWA are tiny insects that are difficult to see without magnification. However, as the adelgids feed, they secrete white, fluffy strands of wax from pores on their body. This wax — called “ovisacs” — covers the adelgids, protecting the insects and their eggs from desiccation and natural enemies. The white ovisacs are most apparent from late fall to early summer, especially on the undersides of shoots, and make it possible for us to identify the HWA most easily in the winter.

Close-up pic: Kelly Oten, North Carolina State University, Bugwood.org Branch pic: Steven Katovich, Bugwood.org

Magnification of an adelgid. Note how large the needle looks in comparison.

Eastern Hemlock,
A tree worth protecting

One of our most beloved evergreens, the eastern hemlock (Tsuga canadensis) is also a critical part of our local ecosystems. Often found along ravines, hillsides, and stream banks, eastern hemlock offer habitat for wildlife and provide shade for streams, effectively lowering stream temperatures and increasing oxygen for fish and other aquatic species. Hemlocks provide aesthetic value and are loved by homeowners. It is estimated that Michigan is home to 170 million eastern hemlock trees.

About our surveys

CAKE CISMA conducts hemlock surveys on public and private properties. You may submit the digital consent form above or request a PDF to print and mail back to us.

When we arrive to survey we will call you to let you know we're at your property and to discuss any questions/concerns you may have about hemlock woolly adelgid. No news is good news, if we don't find anything during our surveys we will not contact you unless requested.

If we do find a suspected HWA infestation we will collect a sample and send it to the Michigan Department of Agriculture for confirmation. You will be notified if the detection is positive, and CAKE CISMA will serve as a resource for you regarding treatment options. Please DO NOT collect samples yourself. CAKE CISMA staff have the required training and permits to collect and ship invasive species material.

Frequently Asked Questions

Why do we survey in the winter?

Cooler temperatures trigger HWA feeding activity, as hemlock woolly adelgids feed, they secrete a white, waxy material that creates ovisacs. These small, round, white masses make it possible to identify infested trees - They're easier to see and we're less likely to spread them in the winter.

Why do we survey properties within 10 miles of the Lake Michigan shoreline?

The area within 10 miles of the Lake Michigan shoreline is the most probable area for new infestations. The adelgids tend to favor the temperatures and conditions found near the lake more than those inland.

Why did I get a letter and my neighbors didn't?

While we would love to send every landowner in our service area a letter, it just isn't feasible for us in terms of financial constraints and staff capacity. Our mailers are sent to randomly selected landowners throughout our service area who are likely to have hemlock trees. Anyone can sign up, but only some landowners receive letters asking them to do so.

I don't live close enough for a survey, what can I do?

You're still encouraged to sign up for a survey, just know that we prioritize properties within the 10-mile buffer zone and only conduct surveys outside of this area if time allows. It's never a bad idea to check up on the health of the trees on your property anyway. If we can't survey for you we highly recommend taking the time to survey yourself (if possible). Check out the website Eyes on the Forest (linked here) to learn how you can monitor trees in your community.

What should I do if I think I've found HWA?

To prevent the spread, please DO NOT move or cut the branch off! Take photos, mark the location, and report the possible infestation to us. We will follow up and will ensure the correct agencies are notified.

Have we ever found HWA in Northern Michigan/the CAKE region?

Yes, in March 2024 an infestation was detected in Western Antrim County near Torch Lake. CAKE CISMA and our partners are actively working with landowners in the affected area to manage the infestation. Check out the press release here.

What should I look for if I'm looking for HWA?

Small, round, white, cottony masses, 1/16" to 1/4".
Found on the twig at the base of the needles on the underside of hemlock tree branches.
Present year-round but most visible November through July.
Note that hemlock woolly adelgid infests eastern hemlock trees, not pines or spruces.

Steven Katovich, Bugwood.org