The Michigan Department of Natural Resources (DNR) is asking people to plan now for spring treatment of hemlock woolly adelgid for those who have hemlock trees on their property.
The invasive species native to Asia, according to the DNR, are small insects that suck sap from hemlock needles and ultimately can cause tree death.
Recommended Videos
Where have infestations been found?
Infestations of hemlock woolly adelgid have been known in Allegan, Antrim, Benzie, Leelanau, Mason, Muskegon, Oceana, Ottawa and Washtenaw counties.
How to identify a hemlock tree
The adelgids feed and form ovisacs only on eastern hemlock trees in Michigan, which is why it’s important to distinguish them from other conifers like pines or spruces.
The DNR suggests looking for the following:
- Cone- or egg-shaped trees up to 75 feet tall.
- Drooping or feathery branches.
- Flat needles growing individually from the sides of twigs.
- Needles that are dark green on top with two parallel, white stripes underneath.
- Papery cones about three-quarters of an inch long that hang downward from branches.
You should look on the undersides of branches for evidence of round, white ovisacs near the base of the needles. Up close, ovisacs look like tiny cotton balls and may appear alone or in clusters.
Treating trees
DNR said products containing either imidacloprid or dinotefuran as the active ingredient and labeled for treating hemlock woolly adelgid effectively combat the insect.
- Imidacloprid moves slowly through trees, taking at least a year to reach the top of a large tree. However, one application will protect the tree for at least four years.
- Dinotefuran moves through hemlock trees more quickly, making it ideal for heavily infested trees. Dinotefuran protects trees for one to two years.
The application of imidacloprid or dinotefuran is simple enough for many landowners to do themselves. Products containing these chemicals are available at garden supply stores and packaged under various trade names in liquid or granular form. Check the label or ask for assistance in selecting the right product.
How to report infested hemlock trees
If you find an infested hemlock tree, you can report it by using the Midwest Invasive Species Information Network online by clicking here.
Reports also can be made by email to MDA-Info@Michigan.gov or by phone to MDARD’s Customer Service Center at 800-292-3939.
Share the location of the infested trees and try to take one or two pictures of infested branches to help confirm identification. To not collect sample branches or twigs.
