Get outdoors with an added purpose: keep a lookout for these forest threats

View as a webpage  /  Share

Maine Forest Service

Be on the Lookout for Invasive Species

National Invasive Species Awareness week is February 28 through March 4. Join the efforts to detect and reduce the spread of invasive species.

We get outdoors for different reasons, and many of us for a multitude of reasons. If you want to add "Giving back to the forest” to your list, take some time to become familiar with how to recognize some of the insects and diseases that threaten our forests and trees and be on the lookout for them on your next outing.

Earlier in the month, we highlighted how winter can be a great time to be on the lookout for hemlock woolly adelgid and emerald ash borer. Here we will cover one of Maine’s newest forest threats, beech leaf disease, and an insect that has not been found in Maine, Asian longhorned beetle.

Beech Leaf Disease

A potentially fatal disease of beech trees from Ohio to Southern New England was first detected in Maine Forests in 2021. In May, landowners in Lincolnville first noticed symptoms of beech leaf disease on one of their frequent walks through their forest. The symptoms were later confirmed to be beech leaf disease. Symptoms of the disease have since been seen in towns throughout Waldo and Knox counties as well as at sites in Lincoln and Penobscot counties. Given the distribution and severity of the symptoms, it is likely this disease has been established in Maine for a while.

Because beech is one of the species prone to holding their leaves through winter (known as marcescent), it is possible to spot banding associated with beech leaf disease this time of year. That banding develops as a result of injuries early in the development of the leaf and persists even after leaf fall. We are interested in learning more about where beech leaf disease is established in Maine and welcome your reports.

University of Maine Cooperative Forest Research Unit has an informative video on beech leaf disease.

Beech leaf in winter showing banding

Interveinal leaf banding is a symptom of beech leaf disease that is visible in the winter. Image: J. Bither ME DACF

Asian Longhorned Beetle

Asian longhorned beetle has not been found in Maine, but we encourage people to be on the lookout for it. This insect is a serious pest of hardwood trees and the target of an eradication program in North America. Early detection is critical to this effort.

This time of year, look for evidence of beetle activity including:

  • Perfectly round exit holes along with egg laying sites.
Round exit hole in bark of maple tree

Exit holes (center) and egg laying sites (above and below exit hole) are signs of Asian longhorned beetle damage that are visible this time of year. Image: J. Formann Orth Massachusetts Department of Agricultural Resources

  • Areas of missing bark revealing past tunneling activity of larvae. Tunnels are oblong in cross-section and are found both on the surface of the wood and within the heart of the tree.
Broken branch in tree

Damaged branches and stems or areas of missing bark may reveal tunneling characteristic of Asian longhorned beetle damage as is seen in this ice-storm damaged tree in Massachusetts. Image: R. Childs UMass Extension

How Can You Help?

Watch the trees around you for signs of invasive forest pests. If you think you have seen evidence of them in a new location, please let us know. You can report them on our on-line form, by email to or by calling (207) 287-2431.

Stay up to date:

Follow: Maine Bug Watch on Facebook or Twitter

Subscribe to Invasive Pest News and Conditions Reports (look for the blue subscribe box).

Report Now!