Bangor reviews Emerald Ash Borer response plan: treatment, removals and a cost-benefit case

Sofia ("Sophie") Cameron, who worked with the city through the University of Maine, presented a completed Emerald Ash Borer Response Plan to the Bangor City Infrastructure Committee Monday, recommending a mix of targeted chemical treatments and prioritized removals to protect public safety and retain urban canopy.

Cameron said the city’s tree inventory identified 8,574 municipal (public) urban trees and 1,854 ash trees — about 20 percent of the city’s urban canopy. Because ash has a high susceptibility to emerald ash borer (EAB) and an expected mortality rate near 98 percent absent intervention, the plan sets a multi-year treatment, removal and replacement approach focused on public safety and canopy resilience.

The inventory and plan matter because many of Bangor’s ash trees are mature and located in high‑use areas; Cameron warned that infested ash becomes brittle and can fail without storm conditions, creating risk to people and property. She said EAB has been detected in neighboring areas, that the city’s work so far has been preemptive and that arrival in Bangor is likely.

Cameron described a treatment strategy using emamectin benzoate, a systemic insecticide injected into a tree’s vascular tissue. She said the plan identifies 250 publicly owned ash trees as treatment candidates: the trees are healthy enough and located where preservation makes public‑value sense. The plan recommends a three‑year treatment cycle using emamectin benzoate, and a nine‑year initial treatment window (three cycles) to span the anticipated ‘‘killing front’’ of the infestation.

Cameron presented a cost‑benefit analysis using established per‑tree benefit values from Kovacs et al. and the city’s inventory. She said the total estimated benefit over nine years for the 250 selected treatment trees is about $461,000 (roughly $1,844 per treated tree). The plan lists treatment costs for the 250 trees at about $26,000 in total (about $104 per tree) and shows that treating is substantially less expensive than removing and replacing those particular trees over the same interval.

The plan also identifies 436 ash trees that the inventory rates as high‑risk and slated for removal; staff differentiated between trees that would require contractor removal and those manageable by the city’s in‑house crew. Cameron said the inventory allowed the city to estimate the portion of removals the city can perform in house versus those that would require outside contractors.

Cameron said roughly 1,168 additional ash trees remain without a fully specified management plan; using a 10‑year horizon and the same valuation approach, the plan estimates those trees would generate about $7,000,000 in ecosystem benefits over a decade (about $6,000 per tree). The plan recommends an expanded treatment and replacement program to capture those benefits, increase species diversity and reduce future pathogen vulnerability.

City staff and committee members discussed next steps. Ben Bridal, City Forester, will lead prioritization of removals and coordinate in‑house work. Cameron said the city plans to treat the first 80 trees this year within existing budget resources and to continue outreach to property owners about private‑property ash, which the city will not treat on private land without owner consent.

Committee members asked for detail on how benefits were calculated. Cameron said the benefit estimate incorporated avoided energy costs, stormwater management, and public‑health correlations used in the referenced study, and that the plan’s financial figures are estimates intended to inform budgeting and next steps.

Several councilors supported early treatment, noting that preemptive action can be materially less expensive and less hazardous than later emergency removals. Staff said they will bring the plan to the tree board for review and that the board will make a recommendation to the Infrastructure Committee.

Committee members were also urged to support public outreach so residents understand treatment options, the limits of municipal authority on private trees, and opportunities to coordinate neighborhood bulk treatments to reduce private costs.