NEWS RELEASE
CHIPPEWA LUCE MACKINAC CONSERVATION DISTRICT
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As the leaves start to change color and the plants around us start dying, the many species of coniferous trees remain a lovely pop of color throughout the winter months. Unfortunately, the snow doesn’t mean we are safe from invasive species. Not yet in the Upper Peninsula,
(HWA) is a grave foe to Hemlock trees and the best time to ensure it has not spread across the Mighty Mac is to survey Hemlock stands in the winter. HWA forms small wool like white ovisacs at the base of needles on Hemlock trees. HWA is also a microscopic mite that cannot be seen by the naked eye until it starts forming ovisacs.
HWA will emerge from ovisacs early-mid spring. They will continue to feed off of trees and will lay the first batch of eggs in late April, early May. After the first batch of eggs hatches, those new mites will lay more eggs and enter a period of dormancy during August. By mid-September, HWA will end its dormancy period and begin feeding off of the tree again. In November they will starts creating wool for the ovisacs of which will be completed by December. It commonly starts at the top of the tree, spreading down throughout warmer months. Within the ovisacs, HWA mites will continue to feed off of Hemlock trees all winter.
In the past, HWA was able to be kept at bay due to the temperatures within the Upper Peninsula during winter. However, with increasingly warmer winters, HWA has been on a northern march for a few years now.
HWA can very quickly and easily take over a stand of Hemlock trees, causing defoliation of the needles which results in hindered photosynthesis. Eventually Hemlock trees will die from HWA. There are not many economically feasible ways to treat HWA infested trees either, as root injections can become costly. Choosing one Hemlock to treat is often the best way to save any Hemlocks as treatment is not a one-year thing and rather a few years of injections.
The main method of management with these trees is finding the infested tree and “quarantining” it which involves cutting down neighboring trees in declining health. Additionally, leaving unaffected Hemlocks alone in a stand with HWA is helpful as these trees could be resistant and helpful in finding a better way to manage HWA.
Due to this and the fact that there are many Hemlock trees within Michigan’s Upper Peninsula, it is essential that as many Hemlocks as possible are surveyed, particularly along the southwest region along Highway 2. Early detection is always the best defense when managing invasive species, so the sooner we find it, the quicker we can quarantine the infected tree(s) before it becomes a bigger problem.
If you notice Hemlock trees on your property that look like they are losing needles on the crown of the tree or just want to make sure your trees are safe, please fill out the form that is linked to the QR code included in this article. Our team will be conducting HWA surveys starting in mid-December and going till April, so be sure to fill out our permission form before it’s too late!
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