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What is Hemlock Woolly Adelgid?

Hemlock woolly Woollyadelgid (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. You can see them with the naked eye, or use binoculars to see higher branches.

Invasive hemlock woolly adelgid has been found in Mason County. Thanks to collaborative efforts between the Michigan Dept. of Natural Resources, regional CISMAs (Cooperative Invasive Species Management Areas) and regional Conservation Districts, HWA was located in Summit Township and Ludington State Park in 2020. Treatments were underway in 2020 to protect the infested trees and those in surrounding areas.

Protecting our Hemlock trees

Treatments were underway in 2020 for the known infested trees and those in surrounding areas. This was handled by West Michigan CISMA thanks to grants provided by the US Forest Service.

Mason-Lake CD staff will continue survey efforts in winter ’20 – ’21 as was done last year on private property, local campgrounds, township parks, etc. to determine if HWA has spread to other areas of the county.  If located, this will trigger a regional response to containing the infestation and working with the landowner to provide treatment on infested trees. We do not want this insect to continue spreading north!

What you can do:

  • Contact us for a free site visit to check out your trees. Just complete and return the permission form to us and we will schedule a visit. Completed forms can be mailed to the address on the form or emailed to This email address is being protected from spambots. You need JavaScript enabled to view it.. CLICK HERE FOR PERMISSION FORM
  • Keep an eye on your trees! 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. To avoid spreading HWA, do not collect sample branches or twigs. Report the find using one of these methods:
    • Contact us via email at This email address is being protected from spambots. You need JavaScript enabled to view it. or phone (231) 757-3707 ext. 5
    • Use the Midwest Invasive Species Information Network (MISIN) online reporting tool or MISIN smartphone app.
  • Remove birdfeeders from areas where hemlock trees are present. Birds may carry these insects to a birdfeeder where they can be picked up and transported by other birds.
  • Be mindful of your hunting and camping gear, RV’s etc. 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.
  • Construction equipment could also spread these insects and other invasives. Ensure they are washed or brushed off before entering and leaving sites!

For a two-sided, pocket sized HWA and hemlock tree identification card please contact our office to pick one up. Great to keep on your fridge as a reminder to check your trees!

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Learn More

Please see the following resources for help with identification, information, and reporting options: