How Do I Control Emerald Ash Borer Infestations in Vermont?

Overview: why emerald ash borer matters in Vermont

Emerald ash borer (Agrilus planipennis), commonly abbreviated EAB, is an invasive beetle that specifically attacks North American ash species. It has killed tens of millions of ash trees across the United States and Canada, altering forest composition, urban canopy cover, and municipal budgets for tree removal and replacement. In Vermont, where ash contributes to both the rural landscape and urban streetscapes, homeowners, landowners, and municipalities face difficult choices: treat to protect valuable trees, remove heavily infested trees to reduce hazard, or accept long-term loss and plan for replacement.
This article gives practical, evidence-based guidance on detecting EAB, deciding when and how to treat, safe removal and disposal practices, biological and cultural control options, and how towns and communities can respond effectively.

How to detect emerald ash borer: signs to watch for

Early detection is critical because EAB larvae live beneath the bark and can severely damage a tree long before canopy symptoms are obvious. Learn to recognize the most reliable signs.

• D-shaped exit holes about 2-3 mm wide on the bark where adults have emerged.
• S-shaped galleries under the bark visible after peeling back loose bark or when branches are pruned.
• Increased woodpecker activity and bark scaling where woodpeckers are stripping bark to eat larvae.
• Progressive canopy thinning and dieback starting in the upper crown; epicormic sprouts (sucker shoots) may appear on the trunk and lower branches.
• Vertical splits or loose bark on branches or trunk in advanced cases.
• Presence of adult beetles in late spring to summer (metallic green, ~8.5 mm long).

If you suspect EAB, make careful observations and document the signs with photographs. Avoid moving suspect firewood, logs, or branches until you understand the level of infestation.

Assessing ash trees: which trees to treat, save, or remove

Not every ash tree should be treated. Assess each tree using these factors:

• Tree value: aesthetic, shade, wildlife habitat, historic or sentimental value.
• Tree health and structure before infestation: generally, trees in good pre-infestation condition respond best to treatment.
• Diameter at breast height (DBH): larger trees hold more structural risk if killed; very small trees may be impractical to treat.
• Proximity to structures, power lines, and high-use areas: dead ash can fall; hazard removal is often prioritized.
• Neighborhood and landscape plan: consider replacement species diversity to avoid future monoculture losses.

A practical decision path:

1. If the tree is unhealthy with extensive canopy dieback and is near people or structures, prioritize removal.
2. If the tree is healthy, high value, and you want to keep it, consider professional treatment.
3. If the tree is small and low-value, plan to remove and replace when convenient.

Chemical control options: what works and when

Chemical treatments can protect ash trees when timed and applied correctly. Professional application is recommended because of the need for correct formulation, dosing, and application technique.

• Emamectin benzoate (trunk injection): Generally the most consistently effective option for protecting large trees. It provides systemic control and typically protects a treated tree for two to three years per application. It is fast-acting and is effective against established heavy infestations when applied correctly by a certified applicator.
• Imidacloprid (soil drench, soil injection, or trunk injection): A systemic neonicotinoid that can be effective, particularly for smaller trees or as part of an integrated program. Uptake from soil treatments depends on soil moisture and rooting depth; it acts more slowly than emamectin and often requires annual application for reliable control.
• Dinotefuran (soil drench or trunk spray/injection): A fast-acting systemic that can provide season-long protection when used properly. It is often chosen where immediate protection is required, but residual protection is shorter than emamectin.

Important application and safety notes:

• Timing: Apply systemic products when the tree is actively transpiring–typically spring through early summer–so the product moves into the canopy. Trunk injections have some seasonal flexibility but follow product label and certified applicator practices.
• Do not use foliar sprays as the primary control for EAB; systemic uptake is necessary to reach larvae under the bark.
• Always follow label directions and work with licensed professionals. Misapplication can reduce efficacy, pose environmental risk, or violate regulations.
• Consider lifecycle and infestation level: emamectin is preferred for heavy infestations and large trees; imidacloprid and dinotefuran are options for smaller trees or supplemental strategies.

Biological and cultural control options

Biological control and cultural practices can reduce spread and contribute to long-term management but are not immediate fixes for heavily infested trees.

• Biological control: Several nonnative parasitoid wasps have been released in North America to attack EAB eggs and larvae. These biocontrol agents have established in some areas and may contribute to gradual suppression of EAB populations over many years. Expect slow, landscape-scale benefits rather than immediate tree rescue.
• Cultural practices: Avoid pruning during adult flight season if it will create fresh wounds that attract beetles. Maintain overall tree health through proper mulching, watering during drought, and avoiding trunk damage. Replace removed ash with diverse, native alternatives to improve long-term resilience.
• Firewood and wood movement: A key cultural control is to never move untreated ash firewood or logs from an infested area. EAB spreads long distances primarily via movement of infested wood. Use only local, certified, or heat-treated firewood.

Removal and disposal: protecting people and slowing spread

When removal is necessary for safety or because treatment is not feasible, follow best practices to minimize risk and spread.

• Prioritize hazardous trees near homes, roads, sidewalks, and utility lines.
• Hire a licensed arborist or tree removal contractor experienced in insect-infested wood. They will ensure safe cutting and proper disposal.
• Disposal recommendations commonly used in the region:
• Chip wood to pieces smaller than 1 inch using a high-chipper when possible, and leave chips on-site for use as mulch.
• Burn wood only where allowed and safe, following local burning rules; consider restrictions if EAB regulations apply.
• Store wood on-site and allow it to dry (and thereby become unsuitable to beetle survival) for a specified period if municipal guidance allows.
• Comply with state and local quarantine or movement restrictions for ash wood and bark. These regulations are intended to slow human-assisted spread of EAB and vary over time and by jurisdiction.

Monitoring and early detection programs

Effective community response depends on monitoring and early detection.

• Visual surveys: Annual inspections of key trees in spring and summer for exit holes, woodpecker damage, and crown thinning.
• Branch sampling: Removing and peeling small sections of bark from branches can reveal S-shaped larval galleries; this should be done carefully and usually by professionals.
• Trap programs: Many cooperative monitoring programs use traps to detect adult beetle presence at a landscape scale. These surveillance efforts are typically coordinated by state agencies or research institutions.

Encourage your town to invest in monitoring, share observations with local Extension or forestry agencies, and support community training to spot EAB signs.

Working with professionals and costs

Contact a certified arborist or a Vermont-licensed pesticide applicator for assessment and treatment. Key points when engaging professionals:

• Ask about their experience with EAB treatments, products they plan to use, and expected effectiveness.
• Request a written treatment plan that includes product name, application method, frequency, cost estimate, and follow-up timeline.
• For removal, ensure contractors carry liability insurance and follow safe operating standards; ask for references.

Cost considerations:

• Treatment costs vary widely by tree size, product, and application method. Expect higher costs for trunk injections on large trees and for repeat applications every 1-3 years depending on product.
• Removal costs depend on tree size, location, complexity, and disposal needs. Municipal budgets should factor in expanded removal and stump grinding over several years as mortality increases.
• Grants, cost-share, or municipal programs may be available to help homeowners or communities manage EAB impacts; ask your local municipal forester, Extension service, or state forestry agency.

Community-level strategies

EAB is a landscape-scale problem that benefits from coordinated local action.

• Inventory: Towns should maintain an ash tree inventory to prioritize removals and treatments strategically.
• Diversification: Replant with a diversity of native species to reduce future pest vulnerability and maintain canopy cover.
• Public outreach: Educate residents on identifying EAB signs, safe firewood practices, and available assistance.
• Sanitation and quarantine enforcement: Enforce or encourage adherence to wood movement guidelines to slow spread.
• Long-term funding: Budget for multi-year removal and replacement programs, and consider municipal contracts for bulk treatment of high-value public trees.

Practical takeaways and next steps for Vermont property owners

• Learn the signs: Familiarize yourself with D-shaped holes, woodpecker damage, and canopy thinning.
• Prioritize trees: Treat healthy, high-value ash if you want to save them; remove hazardous or heavily infested trees near people and infrastructure.
• Use proven chemicals: Emamectin benzoate injections are the most reliable multi-year protection; other systemic products may be appropriate depending on tree size and urgency.
• Hire professionals: Work with licensed applicators and certified arborists for assessment, treatment, and safe removal.
• Stop wood movement: Never transport untreated ash firewood from one area to another; keep or buy local firewood.
• Plan long term: Replace removed ash with diverse species and support municipal inventories and community monitoring.

Emerald ash borer will continue to challenge Vermont forests and urban canopies, but a combination of informed detection, targeted chemical treatments, safe removal and disposal, and community-level planning can greatly reduce hazards and preserve high-value trees. Taking timely, coordinated action will keep people safer, slow the spread of EAB, and speed recovery of the landscape through thoughtful replanting.