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From the Tree Board: Slow the Spread of Invasive Ash Borer

The emerald ash borer is no longer than the diameter of a penny. Photo by Debbie Miller, USDA Forest Service, Bugwood.org.
This summer, the emerald ash borer has been detected in several locations throughout Montpelier. The Montpelier Tree Board and Parks and Trees Department are working on the next steps to continue slowing the spread of this invasive pest, but we need your help.

Here’s what you can do: 

  • Plan ahead! Use the easy-to-follow homeowner’s guide (montpelier-vt.org/DocumentCenter/View/5200/Homeowners-Guide-to-the-Emerald-Ash-Borer) to identify ash trees on your property and determine your best options.
  • Visit the invasive species page of the Tree Board section of the city’s website (montpelier-vt.org/497/Invasive-Species).
  • Contact aellsworth@montpelier-vt.org if you see signs of infection. Our EAB response team will look at your trees and help you make a plan at no cost to you. 
While our efforts to date have helped slow the spread of the invasive insect, it has continued to spread in the city and remains a significant threat to all ash trees. In other areas of the country where it has been found since arriving in Michigan in 2000, whole stands of ash and streets lined with them are now gone. Once a tree is infested, it dies within a few years and at that point branches become quite brittle and, as a result, dangerous and more costly to safely remove. 

Ash trees can be protected against the pest by having a professional inject an insecticide — Emamectin benzoate — a single treatment of which will keep the pest at bay for up to three years at a cost of approximately $10 to $12 per diameter inch; successive treatments can continue for years with good results. Homeowner pesticide treatment is not recommended. If you have a tree that you love dearly or one that, if it becomes infested, will pose a danger, consider injection a good option. All of the large green ash trees in the downtown area, as an example, have been treated.

The insect, only one-half-inch long, lays eggs in the bark of ash trees and when they hatch the larvae bore their way under the bark causing the tree to die. The larvae mature the following spring and adult beetles emerge between July and September, fly a short distance to lay their eggs, and start the cycle again. The green box traps you may have seen hanging in trees around the city are one of the ways we detect where the insects are; they are attracted to them by color and scent and then get caught in the sticky surface of the trap. We also have conducted visual surveys of ash trees in rights-of-ways and trails in Hubbard park looking for indications of infestation.

To date we have found trees infested in four locations in the city (National Life, Hunger Mountain Co-op, Montpelier Civic Center, and upper Corse Street) and in each case have responded with efforts to slow the spread by either removing the trees or injecting them. It is, of course, probable the pest has spread to more locations but has simply evaded detection thus far. 

To help slow the spread, we ask all in the city to be on the lookout of signs of the pest on any ash trees whether in the right-of-way or on your private property; these signs include dieback in the crowns, lighter patches of bark, and masses of sprouts in lower branches. If found, please notify us at aellsworth@montpelier-vt.org. Please note that actually seeing the insects or the exit holes of the adults is nearly impossible. When notified of a suspect tree, we will schedule a time to come investigate further. 

One other critical way to slow the spread is to not move wood from infested ash trees. Having infested wood chipped or burning it onsite as your winter firewood is quite effective at killing any larvae that may be in the tree but moving infested firewood remains a big part of the problem of spreading the pest.

We appreciate the support the city has given to our efforts to safely slow down the spread of EAB and to the many citizens who have helped. Every year in which we can slow EAB is another year we can work on saving the ash trees we have and planting new trees of different species to take their place. Our efforts this fall and next spring are vital to continuing to slow the spread.

John Snell is the chair of the city of Montpelier Tree Board.