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The emerald ash borer is killing millions of ash trees. A new 'biological control' races to save them

The emerald ash borer is killing millions of ash trees. A new 'biological control' races to save them

NORTH ADAMS — “It’s awful, just terrible,” said Thomas Moore, owner of a Williamstown tree service, The Tree Guy. “We’re losing trees like crazy. It’s like a perfect storm.”

That’s word from the front lines of the battle against the emerald ash borer, an invasive species of beetle whose larvae feed on the ash tree’s nutrient transit system beneath the bark.

Ash trees and the EAB can’t co-exist, Moore says. “The tree has no defense against it, and it doesn’t have any predators of any consequence.” More than a third of the trees Moore takes down for customers are ash trees. For one recent customer, he removed four ash trees that were in danger of falling on a house.

The Emerald Ash Borer

The emerald ash borer is native to Asia. It was first found in the Berkshires in 2012.

Here’s the good news: The destructive insect may have met its match through “biological control,” though it will take years of waiting and watching to be sure.

Since 2012, when an emerald ash borer was discovered in Dalton, the species has been wreaking havoc on forests throughout the Berkshires, New England, and most of the rest of the nation, as well as southern Canada.

Millions of ash trees have been lost to the beetle, thousands — maybe millions — of them in New England.


The feeding paths of the larvae can be seen beneath the bark. 

But scientists have discovered three different species of wasp, which like the emerald ash borer are from Asia, whose larvae feed on the larvae of the emerald ash borer.

According to Greg Cox, program director for the Massachusetts Forest Alliance, tests have been conducted to determine the efficacy of this new strategy to contain the spread of the EAB.

“The Forest Service has been releasing the wasps that feed on EAB larvae, but first they had to make sure it wouldn’t create additional problems,” Cox said.

After introducing this species of wasp in test locales, “the tests showed that infection of trees has declined. But it takes lots of them.”

He said the approach wouldn’t wipe out the EABs, but could reduce their status from being a forest killer to being a forest pest.

“We’ll need to build up the population to attack in sufficient numbers that you achieve active control of the EAB spread, but that will take a while,” Cox said. “For the time being, ash trees will remain at risk.”


Jim Moulton, of North Adams Tree & Landscape, displays leaves of an ash tree outside the city's skating rink. Ash trees here are losing foliage to the larvae of the emerald ash borer, an insect that threatens all ash trees in the northern climes of North America. 

According to a U.S. Forest Service publication, regulatory agencies OK’d the first releases of wasps that feed on the emerald ash borer in 2007 in southeastern Michigan forests.

Battling the ash borer: A look at the plan to contain invader ravaging Berkshire trees

The report was co-authored by Prof. Joseph Elkinton, an environmental specialist at the University of Massachusetts.

Since the process was started, the same species have been released in 350 different counties in the U.S. and Canada.

Field studies in several northeastern states showed that younger ash trees “now experience low EAB densities, which are regulated by established populations of the three introduced biocontrol agents,” according to the report.


This North Adams ash tree, outside the city's skating rink, is slowly losing its foliage to the larvae of the emerald ash borer, an insect that threatens all ash trees in the northern climes of North America. 

Specialists hope that younger surviving North American ash trees will be protected and grow to maturity after suppression of EAB populations.

Cox says white ash is a valuable commodity, because it is a lightweight yet strong wood used to manufacture many products such as baseball bats, axe handles, hockey sticks, canoe paddles and furniture.

“It’s also an important part of the local environment,” he said.

'Pretty well infested.' The emerald ash borer's destructive path through the Berkshires

Larger, older ash trees are in particular danger because the the borer prefers broad surfaces on which to lay its eggs — so the bigger the tree, the bigger the threat.

According to the U.S. Department of Agriculture, since its detection in Michigan in 2002, emerald ash borers have killed tens of millions of ash trees in 30 states.

EAB eggs are laid between layers of bark and in bark crevices. Larvae hatch in about a week and bore into the tree, according to the USDA. The larvae go through four feeding stages, and then excavate a pupal chamber in the fall, where they will overwinter as prepupae. Pupation occurs in late spring, and adults begin to emerge through “D”-shaped exit holes in May and early June. Adults will remain active until the end of summer.

One town’s fight

According to Kent Lew, chairman of the Washington Select Board, for the last two years, the town has budgeted $14,000 a year to take down ash trees on roads. The trees, devastated by the borers, are at risk of falling and causing injuries.

Lew said the funding is only enough to take down a few trees a year, but there are many others that should be removed. “It’s a drop in the bucket, really,” Lew said. “We take down maybe 30 trees in a year, but there are thousands of them out there.”

During the past year, the town targeted trees along Washington Mountain and Blots roads.

“They’ve all been infected, are dying and need to come down,” he said. “With the toll it has taken, we have to be proactive about this.”

If a dead or dying tree threatens to take down power lines, the town will call Eversource to handle those instances. But the rest is the town’s responsibility.

Once the trees come down, the town allows neighbors to take the wood for fireplace or fire pit use, while keeping the wood in the immediate area to minimize the spread of EAB.

In Massachusetts, infected trees taken down are prohibited from being moved to other states or counties. The beetle’s spread has progressed so widely that the prohibition has been lifted in most other states.


This North Adams ash tree, outside the city's skating rink, is slowly losing its foliage to the larvae of the emerald ash borer, an insect that threatens all ash trees in the northern climes of North America. 

“I really wish the state would provide some resources,” Lew said. “It is really hard for towns like ours to carry the load.”

Jim Moulton, owner of North Adams Tree and Landscape, said there have been many ash trees to take down, making up most of his removal jobs.

It is a massive national effort.

In Berkshire County, roughly 12 percent of the forest is comprised of ash.

The National Park Service estimates that there are seven to nine billion ash trees in North America. Scientists estimate that EAB will cost billions of dollars nationwide as it kills ash trees, according to Tawny Simisky, an entomologist at UMass.

"The biological control organisms for emerald ash borer are not currently available for sale," she added.

Scott Stafford can be reached at sstafford@berkshireeagle.com or 413-281-4622.

News Reporter

Scott Stafford has been a reporter, photographer, and editor at a variety of publications, including the Dallas Morning News and The Berkshire Eagle.

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