Local foresters are preparing for the inevitable: the arrival of a culprit that, despite its puny size, has ravaged millions nationwide.
Cue the emerald ash borer.
The beetle, a pest that is smaller than a penny, is easy to recognize by its metallic green shell matched with the trail of “tens of millions” dead ash trees left in its wake. Since the early-2000s, officials have detected the emerald ash borer in more than 30 states, with Forest Grove, Ore., being added to the list in June 2022 — its first discovery along the West Coast.
According to urban forester Charles Ray, it’s not a matter of if emerald ash borers will close the roughly 35-mile gap between Forest Grove and Vancouver, but when.
“There was hope there would be controls in stopping (the borer) expansion, but that doesn’t seem like that will happen,” he said.
The beetles devastate ash trees by burrowing under their cambium layer — the tree’s nutrient-dense tissue — and eating their sapwood. In doing so, the borers prevent water from being transported through the tree’s trunk, leading it to die slowly.
At a time when the city of Vancouver is attempting to preserve and grow its urban tree canopy, every tree needs saving or, if it’s removed, must be replaced, Ray said.
To be proactive in reducing ash tree decline, the city of Vancouver is drafting a management plan that outlines the treatment, removal and replacement of the area’s ash trees.
What to look for
Currently, Vancouver’s ash population is unknown but is estimated to be less than 500, at least on public property. This does not include street trees, natural areas or private property.
First and foremost, property owners and landscapers should familiarize themselves with ash trees. Their branch structure features stems that grow directly across from one another and are adorned with round-edged, pointy-tipped compound leaves, typically with five to nine leaflets.
Though troublesome, emerald ash borers tend to leave clues when they are present.
Larvae that hatch within an ash will etch a continuous “S”-shaped tunnel beneath bark as they feed, which can lead to splitting — the result of the tree developing preventive calluses surrounding the galleries. Once adults, emerald ash borers will leave behind “D”-shaped holes in the bark as they set off between June and July.
When ashes are stressed, they may also attempt to overcompensate for internal damage by growing new branches and leaves near their base or on main branches, also known as epicormic sprouting.
Greg Richardson, Cascade Works owner and arborist, said warmer temperatures and shorter winters allow for the beetles to reproduce more and munch on trees further into the season. During droughts, trees can become dehydrated and lose their the ability to protect against pests.
The insects can sense when a tree is strained, almost like a shark smells blood in the water, he said.
“When you start to see symptoms, your chance of saving that tree is usually less than 50 percent,” Richardson added. “It’s all about prevention — an ounce of prevention is worth 100 pounds of cure.”
What to do
Good tree health — in a sense, maintaining its immune system — is at the forefront of keeping it pest-free.
Eric Overholser, owner of Patriot Pest Management, said chemical treatments paired with irrigation can be effective for healthy trees if emerald ash borer infestations are caught early. There is a wide variety of treatments, which should be applied in the spring before the trees bud, and are most effective when emerald ash borer infestations are within 15 miles.
The beetle itself has a short flying range — just a mile to two miles. It’s likely moving through logs, firewood or wood chips.
To stop the potential spread of emerald ash borers, avoid bringing back ash tree materials, such as pallets and firewood, from outside of Washington. Campers should buy firewood where they intend to burn it, and those who operate sawmills or sell susceptible wood products should become acquainted with the telltale signs of the pest, Ray said.
The city of Vancouver will launch an awareness campaign for residents, as well as update its website and social media channels once its emerald ash borer strategy is completed.
Urban Forestry expects to address its emerald ash management plan during its April 15 commission meeting. More details can be found on www.cityofvancouver.us/publicworks/page/urban-forestry-commission.
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