Six Things Every Mainer Should Know About Emerald Ash Borer
Maine is “Vacationland” - it is home to large stretches of natural landscapes and vast forests, including nearly half a billion ash trees that provide a canopy over the state’s great outdoors. Sadly, in the past few years, an invasive pest has entered and is starting to kill Maine’s ash trees.
First identified in North America in 2002, this damaging forest insect from Asia, the emerald ash borer (EAB), has spread quietly across the country, killing millions of trees in the U.S. and Canada. Maine’s first known infestation was discovered in 2018 in Madawaska across the river that divides U.S. and Canada from a newly found EAB infestation in Edmundston, New Brunswick. The northern EAB infestation has only spread to four towns, but the infestation in York county found later in 2018 has since spread eastward and northward into Cumberland and Oxford counties.
Here’s what every Mainer needs to know about emerald ash borer:
1. The emerald ash borer is not letting up.
The emerald ash borer is in two opposite corners of the state. In southern Maine, EAB has spread to 20 towns since it was first reported in 2018. In northern Maine, EAB is spreading at a slower pace. The emerald ash borer cannot be eradicated and is not going away, although scientists and plant health professionals are learning and using new ways to slow its spread.
2. It's an invisible danger.
Not only is the adult beetle very small and hard to detect, it spends the majority of its life cycle under the bark of ash trees. Woodpecker feeding may be the first sign of EAB you can see. Certain woodpeckers, like the hairy and the downy, go after the larvae under the bark. They flick off the outer bark and leave a characteristic “blonding” effect.
3. The cold won’t save your trees.
EAB overwinters as larvae under the bark of trees, so they are protected by most weather elements mother nature throws at them. Extremely cold winter temperatures, such as those recently linked with ‘polar vortexes,’ may kill some of the larvae but will not save Maine’s ash trees. Where climate allows ash trees to grow, EAB can build to populations that can kill them.
4. Every ash tree in Maine is at risk.
EAB will damage all species of ash (Fraxinus spp.) in Maine, including the white ash which is used for baseball bats, fine furniture, tool handles, paddles and many other products; green ash which is a commonly planted street and landscape tree; and black or brown ash which is sacred to the Wabanaki people of the northeastern states and is used to fashion traditional baskets. There are an estimated 400 million ash trees over an inch diameter in Maine.
5. Without help, a death sentence.
All species of ash are vulnerable to the emerald ash borer and without intervention, most will die, and the beetle will continue to spread. In forestlands, Maine DACF in cooperation with the US Department of Agriculture, Animal and Plant Health Inspection Service has been releasing tiny stingless wasps that attack the egg and larval stages of the insect, reducing the populations to give ash tree seedlings a fighting chance.
Trees are not only important in our forests, but also around our homes and in our communities. Although planting new ash trees is not recommended anywhere in Maine, the benefits provided by healthy, established ash already in residential and community landscapes may make them good candidates for protection. Several insecticide products are available to manage emerald ash borer impacts to trees. However, not all ash trees should be treated. Tree location, value, health and cost of treatments are all factors to consider in deciding whether or not to use insecticide treatments.
Trees are also part of our infrastructure, and when they fail, they can damage roads, communication and power lines and buildings. EAB can cause a rapid buildup of dead and dying trees. Anticipating where that wave will hit and reducing and managing the impact from it are important strategies to adapt to this insect.
 Parasitic wasp used for biocontrol of EAB (photo by BillMcNee-Wisconsin DNR), trunk injection to protect ash tree (photo by MSU), infested ash trees easily break and cause damage (photo by Sarah Courtney/Jefferson Township Dads and Moms Facebook group)
6. EAB, and other threats like it, are public and private issues.
Although most trees in Maine are privately owned, we all benefit from a healthy forest. As trees grow, they help slow climate change by removing carbon dioxide from the air, and storing carbon in the trees and soil. They release oxygen into the atmosphere, offer cooling shade, block cold winter winds, attract birds and wildlife, purify our air, prevent soil erosion, and clean our water. EAB and other invasive insects and diseases endanger the health of our forests.
We can all support healthy forests in Maine. Help slow the spread of EAB and other invasive forest pests by using local or certified heat-treated firewood and encouraging others to do the same.
You can help monitor for EAB through visual surveys, participation in a trap tree network and biosurveillance. You can also learn more about other invasive threats to forest health, look out for them, report concerns, and spread word about them to help slow their spread.
 Portland's champion green ash tree courtesy of Friends of Portland Maine Forest City Trees
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