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Emerald Ash Borer and Boston's trees

Emerald Ash Borer is a beetle that kills ash trees when its larvae burrow under the bark and feed on the nutrients that circulate inside the tree. The beetle was first detected in the United States in 2002.

What is Emerald Ash Borer?

About
D-shaped exit holes
About Emerald Ash Borer

Emerald Ash Borer is a beetle that kills ash trees when its larvae burrow under the bark and feed on the nutrients that circulate inside the tree. The beetle was first detected in the United States in 2002. Experts think it probably came from Asia in wood-packing material. The Emerald Ash Borer has been spreading in Boston since it was first found in the Arnold Arboretum in 2014.

basal sprouting
Emerald Ash Borer and Boston's Trees

Some ash trees in Boston’s neighborhoods have started displaying signs of infestation. It may take three to five years for trees to begin showing outward signs of Emerald Ash Borer activity.

Signs of activity include:

  • D-shaped exit holes in the bark of ash trees
  • "Blonding” from woodpecker feeding
  • Dieback in the upper third of the tree canopy
  • Sprouting at the base of the trunk
serpentine galleries
What does Emerald Ash Borer eat?

The pest feeds only on ash trees. But, the Emerald Ash Borer kills 99% of the ash trees it infests. If more than one-third of an infested ash tree is dead due to damage from Emerald Ash Borer, the tree cannot be saved and must be removed.

The invasive beetle has been identified in the neighborhoods of Allston-Brighton, Dorchester, Fenway-Kenmore, Hyde Park, Jamaica Plain, Roslindale, Roxbury, Mattapan, and West Roxbury, as well as the Arnold Arboretum, Franklin Park and the Muddy River area.

Protecting Boston's tree canopy

Steps we're taking

The Boston Parks and Recreation Department is working to ensure the health of our public street trees as well as trees in the parks, squares, and plazas that the Parks Department maintains. We’ll protect healthy trees and remove dead and heavily infested trees to stop the spread of the Emerald Ash Borer. 

We’re also working on a comprehensive Urban Forest Plan to preserve and expand our tree canopy — and the overall quality of life for Bostonians. Increased funding and staffing for tree care will help us respond to pests like Emerald Ash Borer.

How you can help

Look out for public street trees marked for removal or treatment over the coming months. Never move tree material from one location to another.

The Boston Parks and Recreation Department cares for street trees and trees in parks. If you see a street tree or a tree in a public park that you think may be infested with Emerald Ash Borer, contact 3-1-1. If you have questions about identifying ash trees on private property, like the grounds of homes or businesses, contact a certified tree care professional.

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Frequently asked questions

Questions?

Boston is home to approximately 1,817 public street ash trees. That represents about 4.3% of the City’s total street tree population. We are currently inspecting all street and park ash trees to determine the number of infested ash trees.

The City’s Arborist will determine which public street trees must be removed and which can be successfully treated. We’ll need to remove some street trees during the fall and winter of 2021-2022 while the trees are dormant. We will begin preventative injections in the spring of 2022 when the trees are becoming active.

We will inspect all removal sites for new tree planting. We will also prioritize replanting these locations in the next planting season. Street infrastructure has changed since the ash trees were originally planted. Some sites may not be suitable for replanting due to current planting specifications — some examples are conflicts with:

  • underground utilities
  • driveway curb cuts
  • new street light installations, and
  • crosswalk ramps.

We will conduct inspections of public street trees and investigate 311 reports of suspected infestation.

Park trees will be addressed in the next phase of our management plan. We will follow a similar strategy that we are using for the public street trees:

  • assessment
  • treatment of trees that can be saved
  • removal of trees that pose a public safety hazard, and
  • prioritization of removal sites for replanting.

In parks undergoing capital improvement projects, we preemptively treat healthy trees and plant diverse tree species.

The Urban Forest Plan will make recommendations for increased funding and staffing for tree care. Our goal is to better detect and respond to pests like Emerald Ash Borer.

A certified arborist in the Tree Division or a certified arborist contracted by the Tree Division assesses the health of public trees. Utility companies have the right to prune ash trees away from infrastructure. They may also remove dead, dying, or dangerous ash trees that threaten utility lines.

If more than one-third of an infested ash tree is dead due to damage from Emerald Ash Borer, the tree cannot be saved and must be removed. Healthy or lightly affected trees will be treated.

We will prioritize the healthiest trees for treatment, and the most hazardous for removal. Trees may not be replanted in the exact location if the original site is unsuitable.

Property owners should learn to identify ash trees by using the links to resources on this page or visiting their local Boston Public Library branch. If you have ash trees on your property, contact a tree care professional to create a management plan for Emerald Ash Borer.

Ash Tree Identification Guide (pdf, University of Michigan)

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