MIDDLEBURY — Middlebury is preparing for the inevitable arrival of a voracious invader that targets a specific prey.
It’s an invader that measures less than the diameter of a penny, but it attacks in great numbers and won’t be denied.
We’re talking about the emerald ash borer, a beetle that has already munched its way through ash trees in 26 states, causing millions of dollars in damage to forests. And while the ash borer has yet to unleash its devastation on the Green Mountain State, local communities — including Middlebury — are designing plans to deal with the voracious insect.
“It will be much easier if we’re proactive about this,” said Judy Wiger-Grohs, who along with fellow Middlebury Tree Committee member Sally Thodal took the lead in drafting their town’s emerald ash borer preparedness plan.
“At some point, (ash borers) are going to be here, because they are active all around us,” Wiger-Grohs added.
Indeed, ash borers have already been confirmed in the neighboring states of New York, New Hampshire and Massachusetts, as well as in the Canadian province of Quebec.
Left to its own devices, a single ash borer can travel a half-mile per year, with the potential to cover several miles during the adults’ annual June-to-August flight period, according to Middlebury’s preparedness plan. But even more alarming is the extent to which the ash borers can travel greater distances through infested tree nursery stock and firewood.
The beetles infect the crowns of the trees first, making barely discernable entry and exit holes in the bark. Ash borer larvae feed on key nutrients below the bark, contributing to the ultimate demise of the ash tree. And the loss of ash trees could have a profound effect on other tree species, according to Thodal and Wiger-Grohs.
Invasive tree species can take over spots where ash trees once stood, thus crowding out native species such as birch and maples. Native animals used to feeding on insects that are partial to ash trees will lose that source of food. And local ecology and soil chemistry will likely change with a mass die-off of ash, according to the tree committee’s report.
“Once a tree is infected, there are not a lot of options,” Thodal noted, adding, “A big question for Middlebury is, do we want to save particular (ash) trees?”
THREE OPTIONS
The Vermont Urban and Community Forestry Program in 2014 conducted an individual street inventory of all trees, including ash, within the public right-of-way and on public land in downtown Middlebury and East Middlebury. That survey yielded a combined total of 96 ash trees of various maturity and health. The Middlebury Tree Committee has been scouting the town for additional ash trees.
Communities currently have three management options for dealing with emerald ash borers, according to Wiger-Grohs and Thodal: Remove ash trees proactively or reactively; remove them and replace them with resistant, native shade trees; or treat trees with insecticides.
The Tree Committee has compiled a lot of research on the ash borer problem, thanks in part to the University of Vermont Extension Service and the Vermont Agency of Natural Resources. That research — based on the experiences of other states — has revealed that removing vulnerable trees prior to infestation is the more prudent approach.
“This strategy provides time for project planning, as well as an opportunity to plan for and distribute costs,” Middlebury’s ash borer preparedness plan states. “This strategy is cheaper and safer as healthy trees fall in a more predictable manner and are easier to remove.”
Use of insecticides can be effective, but also has its potential drawbacks, according to the report. Those drawbacks include drift of insecticide spray to non-target trees; the need to drill holes for insecticide injection, leaving convenient tunnels for other damaging organisms; and the risk of the insecticide being toxic to other wildlife like birds and bees, and polluting groundwater.
“I personally find it difficult to recommend the use of pesticides,” Thodal said.
Middlebury’s tree committee has drafted a plan proposing, among other things, that:
•  All dead ash trees, as well as those in poor condition, be removed as soon as possible.
•  Larger ash trees with a diameter of 24 inches or more (at breast height) be treated with an insecticide.
•  All other ash trees be removed  and replaced with alternative native trees, at a rate of two replacement trees per ash.
•  The town’s budget include an emerald ash borer line item beginning this year, and in future years, until the ash borer is no longer considered a threat.
The plan also calls for Middlebury residents to be informed of the imminent ash borer threat as soon as possible. Officials reasoned there are many additional, vulnerable ash trees on private property, and those property owners should be advised to take action.
The Middlebury tree committee estimates it would cost the town almost $60,000 to implement the proposed preparedness plan, with the greatest expense being the two-for-one ash replacement plan ($43,000). That plan reflects $250 per replacement tree.
Unfortunately, there are no state or federal funds for local ash borer preparedness efforts, meaning communities and private landowners will have to shoulder the costs. Wiger-Grohs and Thodal said there could be some limited grants for new trees.
The Middlebury Infrastructure Committee has been reviewing the Tree Committee’s proposed ash borer plan, and will ultimately issue a recommendation to the selectboard for a final OK. Then it would be up to local voters to consider the plan in March as part of the fiscal year 2018 municipal budget.
In the meantime, folks should start scrutinizing the tops of their ash trees for the first signs of destruction.
“A lot of people believe ash borers are already here, just not in significant numbers,” Wiger-Grohs said.
Reporter John Flowers is at [email protected].