By Melissa Wagoner
The current trajectory of the invasion of the emerald ash borer (EAB)– a wood boring pest known for its decimation of the ash trees on the East Coast of the United States since its introduction in 2002 – leaves little hope for the future of Oregon’s mature ash trees.
“I think that folks believe that eventually EAB will kill most of the mature ash,” Richard Sniezko, a Center Geneticist for the US Forest Service, said.
According to Sniezko that could mean more than 99 percent of Oregon’s ash – the majority of which are found in the riparian area along rivers and streams – will need replacing, costing the public millions of dollars and having untold consequences on the environment.
“With widespread mortality of ash, it is expected that there will be impacts on local systems, namely the types of plants that will replace ash could be very different,” Wyatt Williams, an Invasive Species Specialist for the Oregon Department of Forestry, said. “Oregon ash is a species that hasn’t been studied very much; there is very little in the peer-reviewed literature. People are starting to pay attention to it now, however, and my guess is that we will learn more about the ‘importance’ of Oregon ash to riparian systems in the Willamette Valley.”
That knowledge may come at a stiff price, however, as EAB – currently quarantined in an area near Forest Grove – makes its way across the state.
“We learned from our counterparts that almost all the native ash in infested areas in the eastern half of the country were killed within ten years or so after the arrival of the invasive emerald ash borer,” Williams said in a press release from the Oregon Department of Forestry.
Remarkably effective at killing off trees, first by laying their eggs under the bark, then – after the larvae hatch – by interrupting the flow of nutrients, effectively starving the tree. EAB is also one of the few invasive insects that mount an attack on an already infected tree.
“You’ll have multiple generations on one tree,” Nick Morris, a Forester with the Oregon Parks and Recreation Department, confirmed. “The ash get hit so hard that it’s a death sentence.”
But it’s not always easy to identify that a tree is infected – at least not at the outset.
“Unfortunately, the die back from emerald ash borer looks like drought stress,” Morris said. “You’re really looking for that top-down death. The first year you would see the tips of the tree won’t come back in the spring. The next year it’ll be a little lower and a little lower, and by year three to five you see the D-shaped exit holes that they produce. By then it’s too late. Not only is the tree dead but the insect has made it to surrounding trees.”
Which is why, rather than relying solely on the currently imposed quarantine and treatment of infected trees, the Oregon Department of Forestry undertook the additional harvest of more than 900,000 ash seeds to further EAB resistance testing and to aid in future replantation.
“If EAB continues on its path… the only way one will have much Oregon ash on the landscape in say 50 years is if a program to develop genetic resistance is undertaken and successful…” Sniezko said. Adding, “this premise is being undertaken for other ash species back East and there is cautious optimism that it is doable.”
Made possible by a federal grant from the USDA Forest Service, the project began with the collection of seeds from 245 mother trees representing 27 distinct populations found throughout Oregon. These seeds were then cleaned and sorted at ODF’s JE Schroeder Seed Orchard facility in St. Paul before being shipped to research facilities in Colorado, Iowa and Cottage Grove, Oregon.
In the meantime, with seeds collected and testing underway, it is down to local foresters, like Morris, to slow the impact of EAB.
“One of the biggest things we’re trying to do as an agency is get the word out,” Morris said. “We’ve always been known for our education and that’s my job, education – to let people know there are things people can do to keep [EAB] at bay.”
One of the most important of those is the cessation of hauling and burning ash.
“That’s one of the words that we’re getting out,” he confirmed. “If you’re traveling with ash firewood and you know it, please let us know… we’re taking that wood and trading them and then treating the wood appropriately. I’ve been putting up ‘burn it where you buy it signs.’”
He’s also put a moratorium, within Oregon State Parks, on planting any new ash trees and – once the trees leaf out this spring – he will begin cataloguing ash groves, monitoring them for infection.
“The plan is to concentrate on the northern Willamette Greenway,” he said.
Because, unlike Silver Falls State Park, which boasts relatively few ash trees, the Willamette Greenway – an area covering more than 255 miles – is home to most of the state’s ash.
“Right now, the generally infested area is right around Forest Grove, but Forest Grove is just a hop, skip and a jump away from the Willamette Greenway,” he said. “And OPRD manages a lot of land in that area.”
It’s an eventuality for which Morris has already prepared.
“Early on I crafted an OPRD response document and sent it out to park managers and said this is how we will respond,” he said.
But chances are, even that response plan will not be enough to save the ash trees in OPRD’s care. Which is why the Department of Forestry’s recent seed collection, focused on harvesting the seeds of trees native to the area, is of such importance.
“Other states, they weren’t able to do that,” Morris pointed out. “Their ash was devastated before they could do seed collection.”
It gives him hope that there is a future for Oregon’s ash.
“If we get to a point where we get the insect under control, we can use the seed to start reforesting,” he said. But it’s a process that will take some time.
Resources to report or review
• To report sightings of emerald ash borer make a report online at the Oregon Invasive Species Council hotline, https://oregoninvasiveshotline.org/reports/create or call 1-866-INVADER.
• More information about the impacts of EAB on Oregon’s urban forests: at https://www.oregon.gov/odf/forestbenefits/pages/foresthealth.aspx
