Friday, May 24, 2019

Emerald Ash Borer Awareness Week: Do your part to protect Maine’s forest

In 2018, emerald ash borer, a tiny wood-boring beetle from Asia, was found in northern Aroostook and York counties in Maine. Emerald ash borer (EAB) is a threat to all ash trees in North America and has already done considerable damage to ash in forests and residential properties across the eastern U.S. In addition to comprising an important part of our forest ecosystem, the wood from ash trees is valuable for flooring, cabinetry, hockey sticks and baseball bats. Many streets in many Maine towns are lined with ash trees and ash trees have been planted in residential landscapes for shade and to increase property values. In Maine, brown ash is an important part of the Wabanaki creation story and culture and has been used for generations for basket weaving.

Image of emerald ash borer. University of Maine photo
Emerald ash borer is a metallic-green, wood-boring beetle, only 1/2" in length. Adult beetles feed on the leaves of ash trees, but the major damage to the tree is caused by the larvae feeding under the bark, making serpentine galleries that, in effect, "girdle" the tree, preventing the transport of water and nutrients and resulting in tree mortality within 3 or 4 years of infestation. Since the beetle itself is small and the larvae feed under the bark and out of sight, most infestations are identified by signs and symptoms of decline in ash trees. 

These include: crown dieback in a vase-shaped pattern in the center of the crown; splits and cracks in the bark; tiny D-shaped exit holes in the bark where adults emerge in spring; evidence of severe woodpecker feeding known as "blonding," with large patches of bark chipped off to reveal the paler ("blond") wood underneath; and epicormic growth, or branches that sprout from the trunk below the crown. There are many other causes of ash decline - native borers, fungal diseases, damage by wind or ice - but if you are concerned about an ash tree and think it might be infested with EAB, look for these signs and symptoms ( images at and report the suspect tree by using the form at or by calling the Maine Department of Agriculture, Forestry and Conservation at (207) 287-2431.

The populations identified in Maine last spring and fall are most likely a result of natural dispersal from existing infestations in New Brunswick and southern New Hampshire. EAB can spread only a few miles a year on its own but can be moved long distances very rapidly in infested timber products, like firewood. The best chance we have to slow the spread of this destructive forest pest is to not move firewood - buy local wood where you intend to burn it! To facilitate this, Maine has joined Firewood Scout, an online directory of vendors of local firewood. Anyone can locate sources of local firewood on the Firewood Scout website at by entering the zip code of your location. In addition, local firewood vendors may list their businesses on the Firewood Scout website at

Currently, there is a quarantine in effect in Maine that includes all of York County and parts of Aroostook County in the St John Valley. This means that it is against the law to move many timber products from these areas without a special compliance agreement. More information about the quarantine and EAB may be found at

We can all help slow the spread of this destructive pest by learning how to recognize ash trees and the signs and symptoms of infestation, by not moving firewood, and by reporting any suspect trees.  If you think you have spotted an infested ash tree, please report your sighting by using the online form at or by calling Maine Department of Agriculture, Forestry and Conservation at (207) 287-2431.

For more information about EAB, its life cycle and how to identify signs of infestation; for information about other invasive forest pests; or to request a presentation on invasive forest pests for your town, garden club or conservation commission, please contact Cumberland County Soil & Water Conservation District at 207-892-4700.  And, please, don't move firewood!

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