The emerald ash borer has been found in Cambridge. Here’s what you need to know.

An emerald ash borer. —Laraine Weschler/Republican-American, via AP, File

If you’ve got a prized ash tree in your yard, beware.

The emerald ash borer, an invasive beetle that feasts its way through ash trees, was found in Cambridge last week.

The City of Cambridge is urging residents who have ash trees on their property to consider either developing a plan with an arborist to treat the trees with a pesticide in order to protect against the beetle or remove and replace the tree.

“[The emerald ash borer] is particularly concerning because of the speed at which it kills Ash trees, generally within 1-3 years,” the city said. “Standing dead ash trees present a public safety risk due to how quickly their brittle branches will fail.”


We spoke with Ken Gooch, forest health program director for the Massachusetts Department of Conservation and Recreation, to learn more about the insect that federal officials say is “responsible for destruction of tens of millions of ash trees in 30 states.”

What is the emerald ash borer, and what will it do to a tree?

A dying ash tree. —Andy Matsko/Republican-Herald via AP

The metallic green beetle was first introduced to the United States in the 1990s, and Gooch said the problem with the insect is that it feeds on the inner bark of the ash trees.

“The inner bark is where all the nutrients and water and everything go up and down in the tree,” he said. “And that’s the area that they eat. So after a while, if they feed in there, the tree can’t feed itself because it eats all that tissue.”

The insect does all its damage while in its larval stage stage, protected under the tree bark from the elements where it can gorge on the tree’s inner bark the ash trees.

Because the emerald ash borer is an invasive insect, it has none of the natural enemies it may have had in its place of origin.

“It’s pretty much just gone rampant, going after ash trees,” Gooch said.

Woodpeckers are the only natural predator for the insect, feeding on the emerald ash borer during its larval stage.


“In fact woodpeckers, if an ash tree is being attacked by woodpeckers, that’s one of the signs that we look for that the emerald ash borer is actually there,” Gooch said.

How does it spread?

Gooch said that while the insect in its mature stage can fly up to about a mile, it generally stays fairly close if other ash trees are nearby. It will even stay on the same ash tree and reinfect it.

“On its own, it doesn’t spread that rapidly,” he said of the insects. “The problem is that people are moving it. People are moving ash.”

The rapid spread of the emerald ash borer is largely due to infected ash being transported by humans in the form of firewood or saw logs.

“That’s why it’s been found in so many places so fast is because people keep moving around the wood,” Gooch said.

What can be done to prevent or slow an infestation?

The markings left from emerald ash borer larvae on an ash tree. —Mike Groll / AP, File

The biggest step to slowing the spread of the beetle is limiting the human-assisted movement of infected ash wood.

Gooch said if you’re having work done on the ash trees on your property, make sure that any ash wood is chipped down to about inch-sized pieces, ensuring the insect can’t survive.

“Or if you have to leave the wood, leave it on site,” Gooch said. “Don’t be moving ash wood around because that’s how the insect is spreading.”

How bad is it in Massachusetts?

The emerald ash borer is in all five other New England states, and it has been found in 42 municipalities across Massachusetts.


“The entire state of Massachusetts is currently part of the national quarantined zone, limiting the movement of all hardwood firewood and green wood products, nursery stock, and any plant materials from any ash species in an effort to stop the spread of the beetle,” according to DCR.

Gooch said the destructive beetle was first found in the western part of the Bay State in the Berkshires in 2012.

“There’s a lot of dead ash trees out in the area now,” he said. “We expected between five and seven years that you’d start to see the build-up in larger and larger numbers. Then the trees start dying because the population of the insect just overcomes any ash trees that are out there. That’s happening out in and around Pittsfield and all the surrounding communities where we know the emerald ash borer is.”

The insect is being found in more locations by state officials, he said.

An adult emerald ash borer. —Minnesota Department of Natural Resources / AP, File

The insect was found in Somerville this year and in Waltham and Newton a couple of years ago.

“Cambridge is not unexpected because we found it in Boston back in 2015 at the Arnold Arboretum,” Gooch said. “We found it on a sticky trap; we didn’t find it in a tree. In the Boston area, we’ve generally just found it in traps. We haven’t found a lot in trees. There’s a very small population of ash trees in the Greater Boston area.”

Ash trees are typically used as street trees in urban areas, which means if they become infected the city runs the risk of losing the street coverage. Not to mention that a dying tree is a potential safety hazard.

“Communities have to make a choice about whether they want to save the trees by treating them with pesticides or come up with a plan to start removing them as they become infested and replacing them,” Gooch said. “Both things are costly. Both things are a cost to the community.”

The problem, he said, is when communities aren’t prepared for the arrival of the devastating beetle or don’t have funds to deal with it once it is found.

“Cambridge has been very good about being proactive,” Gooch said. “They’ve been treating their trees for three years now. They’re proactive. They knew it was coming and were ahead of the curve.”

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