Ten Things to Know About Emerald Ash Borer in Maine

Maine Department of Agriculture, Conservation and Forestry sent this bulletin at 05/22/2025 12:07 PM EDT

Invasives Species

This week is Emerald Ash Borer Awareness Week.
Here’s what’s going on in Maine.

Emerald ash borer adult (photo by Ryan Armbrust, Bugwood.org), emerald ash borer larval tunneling under bark of firewood surrendered to Maine Foerst Rangers (photo by MFS, MDACF), tree tag to alert public of emerald ash borer and the value of ash trees (photo by MDACF)

Large stretches of natural landscapes and vast forests make Maine “Vacationland.” Nearly half a billion ash trees add to the wooded canopy over the state’s great outdoors and picturesque communities. Sadly, the emerald ash borer, first seen in Maine in 2018, is starting to topple Maine’s ash trees.

First found in the U.S. in 2002, this tiny, destructive wood-boring insect from Asia spread quickly and quietly across the country, killing hundreds of millions of ash trees as it spread. Firewood movement has helped speed this expansion. Sticks of firewood from infested ash trees carried from home to campgrounds and camps have also carried hidden emerald ash borers. Maine and other states have regulated firewood movement and worked together to spread the word—firewood carries deadly forest pests. However, new infestations of emerald ash borer and other destructive pests and pathogens continue to be caused by firewood transport.

Ten Things to Know About Emerald Ash Borer in Maine.

The emerald ash borer (EAB) is not letting up. Now firmly established in southern and northern Maine, EAB will never go away. But it only moves a few miles per year on its own. Moving wood from an infested area to an uninfested area will spread the beetle faster. Human-assisted movement is likely the cause of the scattered pattern of EAB establishment in Maine. Most recently, EAB was found in Belfast (Waldo County) and Bar Harbor (Hancock County), reported by professional arborists. Updated detection map
EAB is an invisible danger. Not only is the adult beetle tiny and hard to detect, but it also spends most of its life cycle as a larva under the bark of ash trees. Visible signs of its presence are not obvious. Once populations in a tree build up, you may notice outward signs of woodpecker feeding, called “blonding”. The tree is infested by this time and should not be cut up and moved to a new area.
Every ash tree in Maine is at risk. EAB will attack all true ash species (in the Fraxinus genus) in the state. Ash species found in Maine forests are white, green, and brown, and others, such as European ash, were planted in cities and towns. EAB will attack all these species. Mountain ash (Sorbus spp.) is not susceptible.
Cold winters won’t save your trees. Because EAB overwinters as larvae under the bark of trees, they are protected from most weather elements Mother Nature throws at a Maine winter. Extremely cold “polar vortexes” (which are rare) may kill some of the larvae, but they will not reduce EAB populations to the point of saving trees.
Biocontrol efforts are trying to slow EAB. State officials and land managers are keeping up with the latest research to slow the spread of emerald ash borer and protect ash trees. Parasitoids that attack EAB larvae and eggs are being released in hopes of establishing a balance that will reduce EAB populations.
Treatment saves trees. As EAB approaches an area, healthy ash trees can be treated with a systemic insecticide to keep street and yard trees alive and help them recover from early infestations and to keep seed bearing ash in our forests. Treating healthy trees is more cost-efficient than removing them. A licensed pesticide applicator can help.
Planting new ash trees is not recommended. Until the EAB population has subsided, planting new ash trees in landscape and ornamental settings is not recommended.
EAB is a public and private issue. Infested ash trees decline and become brittle quickly. Be aware that an infested ash tree on your property could cause injury or damage if its branches or the tree itself falls.
Early detection saves lives. The earlier EAB is found, the more options there are to manage it. Help look for EAB through visual surveys, participation in a trap tree network, biosurveillance and spreading the word about this pest.
Slow the spread. Be part of the solution: keep tabs on where EAB infestations have been found. Use local firewood, or travel with certified heat-treated firewood, and encourage others to do the same. Reminder: seasoned and kiln-dried do not count as certified heat-treated. Storm related brush could include ash that is infested with EAB. Any ash tree debris is best disposed on site.

There is hope. Introduced parasitoids, trees tolerant to damage by EAB, efforts to prevent a genetic bottleneck through insecticide treatments and preservation of ash seeds, and a community of people engaged in keeping ash all provide hope for the future of ash.

You can be part of the solution: choose to use local or heat treated firewood; initiate a plan for the ash trees in your community, or start in your dooryard; look out for new areas of EAB and let us know if you see any.