Hemlock Woolly Adelgid

What is Hemlock Woolly Adelgid?

Hemlock Woolly Adelgid (HWA) is an invasive insect native to eastern Asia that sucks sap from eastern hemlock tree branches and can kill a tree in 4 to 10 years if not treated.

HWA can be identified by its white, cottony ovisacs on the undersides of hemlock branches, near the base of the needles. The ovisacs may appear alone or in clusters. Late fall through early spring is the best time to check hemlock trees for the presence of HWA.

Eastern hemlocks are a unique keystone species of Michigan’s forests. They often occur on steep dunes or along rivers. They prevent soil erosion, provide critical shelter for animals like whitetail deer, porcupines, and songbirds, and shade and cool coldwater trout streams. Losing hemlocks to HWA would drastically alter the environment that wildlife depend on. By treating hemlocks for HWA, we slow the spread of this insect in our community and ensure we don't lose the valuable benefits of hemlock.

Mason-Lake Conservation District's HWA crew is grant-funded to look for and treat HWA on private property in Mason and Manistee counties and provide guidance to landowners on how to best manage HWA on their properties. See below to sign up or contact us for more information at the number at the bottom of the page.

Why is it important?

Trees on the right are healthy and lush after an HWA infestation was treated 4 years prior with systemic pesticides.

Photo: Effects of HWA in Muskegon County, MI

Where is HWA Currently Located?

HWA was first detected in Ottawa County, MI in 2015 and has moved north since then. It was first detected in Mason County in 2020. It is known to spread within 10 miles of the lakeshore. A tiny insect, it can be spread by wind, birds, or human, vehicle, or animal movement, especially from April - July when crawlers are mobile.

Taking Action Against Hemlock Wooly Adelgid (HWA)

Concerned about your hemlocks and want to protect them from HWA?
The process is simple—sign up, opt in, and we’ll handle the treatment.

A property survey is the first step toward protecting your hemlock trees from Hemlock Woolly Adelgid (HWA). During this visit, our trained crew will examine your hemlocks for signs of infestation and collect details needed to provide a treatment quote.

To request a survey, simply call our office, email our crew, or fill out our online form. Once we receive your request, we will add your property to our work list. You do not need to be home during the visit, though you're welcome to join us on-site if you’d like.

Property Survey For HWA Detection

Email HWA Crew

Online Form

If HWA is confirmed on your property, our team will offer treatment options based on the survey results. We’ll provide a quote, and if you choose to move forward, a service agreement will be created between you and our office. Treatment will be scheduled for the appropriate time during the summer season, depending on availability.

Our crew uses a systemic insecticide, imidacloprid, which is applied either by injecting large trees or spraying the base of smaller ones. These methods target the treatment to the tree and minimize environmental impacts. The same active ingredient is commonly used in flea and tick medications for pets. One treatment protects the tree for 4–7 years.

I Have HWA On My Property - What Now?

Some limited funding may be available to help reduce the cost of treatment. Depending on available resources, cost-share assistance or partial grant coverage may apply if you choose to hire our team for treatment. We will discuss any current options with you after your property has been surveyed and a quote has been prepared.

Cost-Share and Funding Assistance

What Can You Do As A Landowner?

Look at undersides of branches in December through March for small, white ovisacs. If found, note the location of the tree and, if possible, take photos of the infested branch. Report the finding to your local conservation district or at one of the reporting websites below. To avoid spreading HWA, do not collect sample branches or twigs.
from areas where hemlock trees are present, or move them at least 100 feet from hemlocks. Birds may carry these insects to a birdfeeder where they can be picked up and transported by other birds.
If you are in areas with hemlock trees, just brushing against an infested tree could bring these insects along for the ride! Run clothing through a dryer and wash or brush off gear and vehicles before moving to a new area. This is especially important from April-July when HWA crawlers are mobile.
Consider pruning low-hanging hemlock branches especially along roadways or driveways. Anecdotal evidence suggests this could help prevent infestation spread along high traffic areas.
Don't move hemlock brush or downed material off your property. The best option is to burn on-site. Transport to a disposal site with no hemlocks within 100 yards is allowed, if tightly covered when transported from March-October. Michigan currently is under a quarantine through the Michigan Department of Ag and Rural Development that restricts the movement of hemlock material in counties with HWA. See below links for more information.