Hemlock Woolly Adelgid

What is it and why should we care?

Hemlock Woolly Adelgid appears on Canadian Hemlock trees, tsuga canadensis, as puffy, white, cottony patches similar to mealy bugs on house plants. The cottony mass protects the small sucking insect inside which causes early dying and can eventually lead to tree mortality. Here in Maine, it is found primarily along the coast, but is spreading. No outbreaks have been found in Aroostook County, but if we improperly carry firewood from coastal Maine, inland, we could spread it along with several other forest pests. We have many mature hemlock trees in our forests and although they are not usually harvested due to shake, (splitting of the wood within the tree by strong winds), these trees act as a very much needed watershed; keep the waters cool in the brooks and streams for cold water species. Since Hemlock is usually found near lakes and streams they contribute to Maine’s water quality. Canadian hemlock is also a popular landscape tree as it can tolerate heavy shearing to keep it small. This species also provides nesting sites for songbirds and winter protection. Deer like to yard up under mature hemlock as the canopy keeps the snow off of them. They have to be close to browse, however.

What can you do?

From late-October through July is the best time to monitor for hemlock woolly adelgid. The woolly masses are usually attached at the base of the needles on the twigs. Other conifer species can have adelgids, but hemlock woolly adelgid is only found on hemlocks.

You can reduce the spread by pruning live hemlock branches from trees where people or equipment are most likely to come in contact with the trees. This will prevent a “free ride” for the adelgid to other non-infected trees. A major way of preventing spread is by not transporting firewood! Buy heat-treated firewood when you arrive at your destination. This may seem expensive, but if we kill all of our forests by transporting diseases and insects we won’t have any forests to recreate in. Many camp sites will allow you to gather downed, dead wood, but it is best to ask before you do.

If you think you have found woolly adelgid in Aroostook County you should call or email the Maine Forest Service at foresthealth@maine.gov or 207-287-2431.

Contact the Central Aroostook Soil and Water Conservation District for pictures of Hemlock Woolly Adelgid.