Field Notes

New hope for Vermont’s ash trees

5 min read / September 13, 2024

Delivering “vaccination shots” against the Emerald Ash Borer

On a buggy, humid morning in late June, it took two people to wrap a tape measure around Big Jim. The massive white ash, which lives deep in an ash grove in the Catamount Community Forest, is one of the largest in the state.

Big Jim is named for Jim McCullough, the forest’s former landowner who conserved the property with VLT and sold it to the Town of Williston in 2019. And while Jim’s legacy endures, his namesake tree and the rest of Vermont’s ash trees may not.

Vermont’s ash trees are under grave threat from the Emerald Ash Borer (EAB), a non-native insect that has already killed tens of millions of ash trees around the country. Fortunately, tree stewards across the region are doing something about it.

Ash: A hardwood hero

Vermont’s ash trees, which make up about five percent of the state’s forests, provide unique and important benefits for our environment and economy. They support hundreds of species of wildlife, while their fallen leaves retain nutrients that improve the soil. Their high-quality lumber is used in wood products and flooring. Black ashes, found in the state in lower-lying wetlands, have been used by Indigenous people for basket making, ceremonies, medicine, and art for millennia.

The Emerald Ash Borer isn’t native to North America, which means it has no natural predators to keep its numbers in check. Because VLT plays a key role in improving forest health on conserved land, our staff have been actively monitoring ash trees since 2019 and educating forest landowners about how to manage their woods to slow the spread of EAB. In 2021, VLT forester Caitlin Cusack added a new tool to our ash management toolbelt: injecting ash tree stems with insecticide.

A “shot” that keeps trees healthy

It turns out trees, like humans, can receive shots to keep them healthy. EAB lays its eggs in the furrows of ash bark, killing the tree as their larvae eat their way through the inner bark. Certified professionals can drill tiny holes into the base of an ash tree’s trunk to inject a specially formulated insecticide solution that kills those larvae. When performed every two to three years, this injection is currently the most effective protection against EAB for individual ash trees.

In 2020, Caitlin sought to bring the treatment to Vermont’s ash trees. She applied for a grant from the Forest Service to purchase tree injection equipment for use on forestland VLT owns. Already certified as a commercial pesticide applicator, she was soon “inoculating” small groves of ash trees against EAB.

“It’s something very tangible that we can do on the properties we own and steward,” she said. “We’re a nimble nonprofit, and we can be part of the solution.”

Photo credit: Art Wagner, USDA – APHIS, Bugwood.org

Testing the approach

Caitlin treated ten ash groves on VLT property between 2021 and 2024 and lent the injection equipment to other landowners, including the Catamount forest in Williston She coordinated that treatment with Terry Maron, who serves on the town’s Catamount Community Forest Management Committee. Terry is a passionate advocate for removing invasive species in the forest where possible. She said the committee spends as much as half its annual budget on invasives removal.

“There are a lot of invasives, but just the little you do can make a difference,” Terry said. “Some people get overwhelmed and say why even bother because there’s so much of it. But you can see progress, you know, when you take small steps.”

Last year, Caitlin alerted Terry to a new program that helps landowners cover the cost to treat their trees. Terry coordinated this year’s second round of treatment through Arborjet, a tree care solutions company that has donated injection equipment and technical assistance as part of its Saving America’s Iconic Trees campaign.

So far, so good

This year’s treatment was delivered by Arborjet’s Kevin Brewer and Kris Dulmer, a Vermont arborist with a passion for discovering and saving Vermont’s large trees. Terry was on hand to help locate all the previously treated ash trees and assess their growth. Even with EAB sightings in Vermont on the rise, these ash trees continue to flourish. As a result of the team’s collective efforts, 11 white ash trees are safe from EAB until their next treatment in 2026.

VLT has also performed ash treatments on 10 properties that we own across the state, from Bluffside Farm, near the Canadian border, to Whetstone Woods in Brattleboro. At each site, Caitlin identified a “preservation patch” and treated between 12 and 20 ash trees — mostly female and mostly white ash, with some black ash included where possible — to protect a total of about 150 ash trees.

“Our main goal is to preserve the genetic diversity of ash species, so we’re treating small groups of trees in many different parts of the state,” Caitlin said. “We are also partnering with The Nature Conservancy Vermont, the Appalachian Trail Conservancy, the Vermont Institute of Natural Science, and the Equinox Preservation Trust to share expertise, lend equipment, and hopefully protect even more of the gene pool.”

Buying time to develop largescale solutions

Ash injections are time-intensive and costly, which makes them impractical as a largescale solution to EAB. Still, the treatments help safeguard genetic diversity and sites for future seed collection as we learn more about how to protect these magnificent trees. In the case of Catamount, the treatments also preserve culturally important trees like Big Jim.

Other investments in the future of ash are equally important. Although millions of ash trees have died, some trees have expressed genetic resistance to EAB. These trees are called “lingering ash.” Scientists are breeding lingering ash to increase their offspring’s resistance to EAB, with the hope that the saplings can be used in future restoration efforts. Forest managers can help by leaving plenty of sexually mature healthy ash trees standing to monitor their resistance to EAB over time. VLT has set up several research plots to monitor and identify lingering ash through the Monitoring and Managing Ash (MaMA) research project.

Other organizations are saving ash seeds to create a seed bank for future plantings. Landowners can also play a role in regenerating ash and then protecting young ash trees from deer browse. Together, these actions help buy time for scientists and ecologists to research and develop larger-scale or biological solutions.

Fortunately, in the meantime, Big Jim isn’t going anywhere.