Energy & Environment

Invasive emerald ash borer discovered in Bristol

View from Bristol Cliffs of the town, where an emerald ash borer was recently found. Photo by Travis Wendel

Caroline Slack is a reporter for Community News Service, a collaboration with the University of Vermont’s Reporting & Documentary Storytelling program.

The emerald ash borer’s continued infestation of Vermont has spread to Addison County with a new discovery of the pest confirmed this month in Bristol, according to state forestry officials.

The most recent newsletter on Insect and Disease Observations published by the Vermont Department of Forests, Parks and Recreation describes a confirmed sighting of the insect on June 4.

“A consulting forester in Bristol was looking around town, noticed [an infested] tree and reported it,” said Barbara Schultz, forest health program manager at Forests, Parks and Recreation. The insect, a native of Asia, was first discovered in the United States in 2002 in Michigan and has since spread to 35 states including Vermont, according to the U.S. Department of Agriculture.

Though not invasive in its native habitat, it has done significant damage to the ash tree population in North America, where its feeding cycle and a lack of natural predators allow it to kill ash trees rapidly.

The beetle was first found in Vermont in February 2018 in Orange County. The recent discovery in Bristol now means that the ash borer is confirmed in six Vermont counties: Addison, Bennington, Caledonia, Grand Isle, Orange and Washington, according to the state Agency of Natural Resources. Other reports have suggested that the insect actually could be present in eight counties, but those have not been fully confirmed.

Experts on the insect explain that the infestation found in Bristol was not new, as the damage caused by borers is hard to detect in its early stages. The larvae tunnel under the bark, damaging the tree’s vascular system, so the insect is not visible until it turns into its beetle form and emerges from under the bark.

“This infestation has been going for several years — it was not an immediate spread,” Schultz said. “Infestations are very difficult to find until they are advanced.”

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Now that emerald ash borer has been confirmed both north and south of Chittenden County in Grand Isle and Addison counties, forestry officials fully expect to see it on Chittenden County trees.

Chittenden County Forester Ethan Tapper said that it is possible that the insect is already present in Chittenden County but has not been spotted yet. “It could be here, we just don’t know,” he said.

Emerald Ash Borer

Inner bark of a green ash tree killed by the Emerald Ash Borer beetle. File photo

Ash trees make up 5% of Vermont’s forests, and in some areas, ash trees comprise 40-80% of the forest tree population. Schultz and Tapper stress that these trees are essential to the health and biodiversity of the Vermont ecosystem.

“Forests are healthy in their diversity,” Tapper said. “Having a really diverse forest comprised of many different species of trees growing in different ways is part of what makes them healthy.”

In addition to predation from the emerald ash borer, ash trees are also experiencing “ash decline,” an unrelated dieback of ash trees due to fungal and environmental factors, Tapper said. He predicts that Vermont will inevitably lose the majority of its ashes.

Vermont forests are populated by three species of ash tree — the white ash, the green ash and the black ash. Schultz said that some trees are more resistant to the borer than others. Forestry officials hope that some ash species can resist the borers and that supplemental steps such as introducing natural predators to the environment will control emerald ash borer populations.

Last week, U.S. Rep. Peter Welch, D-Vt., announced he had introduced a bill that would, among other forest protection measures, provide funding for research on the emerald ash borer.

The Invasive Species Prevention and Forest Restoration Act would create a federal grant program to fund research initiatives on invasive species. It would also increase the federal Animal and Plant Health Inspection Service’s access to emergency funding to implement research findings.

Schultz described the bill as a “broad” response to the recovery of Vermont forests rather than direct action against the emerald ash borer.

“Our focus is to maintain the resilience of our ecosystem,” Schultz said. “It’s an insect we’ve only known for 17 years. We still have a lot to learn about this bug.”

Across the state, municipalities and landowners are beginning to take stock of their trees to determine how to either protect or replace vulnerable ash trees. Those designated for preservation will require treatment with a pesticide, which will be costly. That’s leading some communities to begin replacing ash trees before emerald ash borer damage destroys them.

An adult emerald ash borer, an insect first found in Vermont in February. Vermont Invasive photo

While the beetle travels on its own, its spread is accelerated when humans unknowingly transport infested firewood or debris from one town to another, Tapper said. A good example was the discovery of the beetle in South Hero last year that was centered around a campground.

Tapper and Schultz both recommend that those headed to campgrounds buy local firewood rather than transporting wood across counties in order to slow the spread of the borer.

Forestry officials also say that they can use some help from the public in watching for new infestations.

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“Folks should learn to identify ash borers and report suspects,” Schultz said. The beetle has a bright, metallic green shell and is about the size of a penny. Adult beetles exit ash trees upon maturity, leaving distinctive “D- shaped” holes in the bark.

“We’re not going to be able to eradicate the emerald ash borer,” Schultz said. “We’re going to have to learn to live with them.”

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Caroline Slack

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