Ash Trees in Vermont: Understanding the Limits of Treatment in the Era of the Emerald Ash Borer
Ash trees have long been an integral part of Vermont’s landscapes, from the shaded avenues of Burlington to the riparian woodlands and wetlands of Addison County. They contribute not only aesthetic beauty but also ecological and cultural value. Vermont is home to three native ash species: white ash (Fraxinus americana), green ash (Fraxinus pennsylvanica), and black ash (Fraxinus nigra), the latter of which holds deep cultural significance for traditional Abenaki basketmaking. Collectively, ash species constitute approximately five percent of the state’s forests, with higher concentrations in northern wetlands, floodplains, and roadside plantings. Their ecological contributions are manifold: they provide critical habitat for birds and mammals, stabilize soils, moderate stormwater runoff, and offer straight-grained, durable timber. The loss of ash, therefore, is not merely a matter of individual trees dying—it represents a profound disruption to Vermont’s ecological fabric and cultural heritage.
The arrival of the emerald ash borer (Agrilus planipennis), an invasive beetle native to Asia, has fundamentally altered the management calculus for Vermont’s ash. Adult beetles lay eggs in bark crevices, and their larvae tunnel through the cambium and phloem, disrupting the transport of water and nutrients and leading to tree mortality, often within two to four years of infestation. EAB populations spread rapidly and are effectively impossible to contain across the state, leaving every ash tree vulnerable once the pest arrives in a given locality. This has prompted municipalities, landowners, and homeowners to confront difficult choices regarding treatment and removal.
Currently, injectable systemic insecticides such as emamectin benzoate represent the most effective method for prolonging the life of individual trees. When applied correctly, these treatments can protect a healthy, minimally infested tree for two to three years. They are particularly valuable for high-profile trees in urban landscapes, parks, or properties where preserving shade, aesthetics, or historical value is a priority. Treatments provide a temporary reprieve, allowing stakeholders time to plan for eventual tree removal or species replacement.
However, chemical treatment is, by its nature, a temporary intervention. Treatments require repetition every two to three years, creating cumulative costs that can be prohibitive for municipalities responsible for managing thousands of roadside trees. Access is limited; remote forest trees are impractical to treat at scale, confining the approach largely to high-value, accessible specimens. Moreover, treatment protects only the individual tree and does nothing to reduce the surrounding EAB population, meaning the pest continues to proliferate unabated. Even treated trees may experience declining health over time due to repeated chemical injections, drought stress, or other environmental pressures. Interrupting the treatment cycle leaves trees highly vulnerable to reinfestation, creating a dependence on continual chemical intervention.
For Vermont, the implications are clear: treatment is a bridge, not a solution. Municipalities are using targeted treatment strategies for downtown streetscapes and historically significant trees, while simultaneously planning for removal and replacement. Homeowners may extend the life of cherished ash trees for a decade or more, but the eventual need for removal is almost inevitable. In forests, the majority of ash will succumb to EAB, with only a small fraction potentially surviving if resistant genotypes are present. Consequently, long-term forest composition is expected to shift significantly, altering habitat availability, nutrient cycling, and landscape aesthetics.
The path forward emphasizes diversification and ecological foresight. Replacing ash with a mixture of resilient native species—such as maples, oaks, hackberry, and disease-resistant elms—can restore ecosystem function, enhance resilience, and maintain aesthetic and structural diversity in Vermont’s landscapes. Cultural preservation, particularly of black ash groves of significance to Abenaki communities, requires careful protection and management for as long as possible. Researchers are investigating biological control options and selecting for EAB-resistant ash trees, offering potential long-term solutions, but these remain years, if not decades, away from wide-scale applicability.
In conclusion, chemical treatments for ash in Vermont should be understood as a temporary strategy—a way to preserve trees for a limited period rather than a permanent remedy. They allow Vermonters to safeguard valued trees while planning for replacement and ecological transition. By confronting the reality of the emerald ash borer, landowners, municipalities, and communities can make proactive decisions that protect existing ecological and cultural values while fostering a more diverse, resilient forest for the future. Strategic treatment combined with thoughtful replanting represents the most effective approach to navigating the inevitability of ash loss in Vermont’s landscapes.
