Zia Corum/The Mossy Log
On Sept. 10, Oregon forestry officials announced that the invasive emerald ash borer was found in Portland. This beetle is detrimental to the forestry of Portland. While all of the state’s tree species have an important role to play in the city’s ecosystem, one species in particular — the Oregon ash — faces a threat from this invasive bug that may wipe it from our forests.
The emerald ash borer, as it is commonly referred to, is a species native to Northeastern Asia that lays its eggs on the bark of ash trees. The larvae will hatch and bore into the tree, living inside the trunk for up to two years before chewing their way out, leaving a distinct D-shaped hole and flying to another ash tree to begin the cycle again.
Tree experts expect that it will only be a matter of time before the beetle wipes out 99% of the ash trees in Oregon. This loss could lead to the degradation of water supplies, flooding and the death of many fish in our waterways, as well as the thinning of the canopy in residential areas.
In June 2002, five entomologists in Michigan were concerned about a major decline in the health of ash trees in Detroit. They discovered that emerald ash borers had been the cause of these trees’ deaths. Since then, the emerald ash borer has spread across the continent and killed more than 100 million ash trees across the East Coast and the Midwest.
In anticipation of the emerald ash borer’s arrival in Oregon, the City of Portland removed the Oregon ash from the list of approved street trees in 2019. In 2022, the beetle was identified for the first time in a parking lot in Forest Grove, Oregon.
To stem the spread, in August 2024 the Oregon Department of Agriculture (ODA) began a quarantine preventing the transport of wood across counties. Wyatt Williams, an invasive species specialist in the Oregon Department of Forestry, suspects that the beetle may have been in the state for several years before its identification.
“The extent of dieback suggests that (emerald ash borer) may have been present for a number of years at the site but went unnoticed given the difficult access and dense vegetation, which includes a mix of oak and conifers,” Williams said in an interview with KGW News.
In order to understand borer systems, The Mossy Log spoke with Margaret Metz, a researcher and associate professor of biology at Lewis & Clark who specializes in plant pathology. Metz compared the current invasive spread of the emerald ash borer to the chestnut blight infection of 1904 on the East Coast, caused by an invasive fungus, which led to the death of thousands of chestnut trees. She used this example to point out the cascading impact that an invasive species can have on an entire region’s ecology.
“They’re laying their eggs in tunnels, and then the larvae are tunneling around and feeding on material. If you cause enough damage around a tree trunk, you can cut off the flow of nutrients and water, and that’s how trees often die from something like this … we’ve seen lots of examples where invasive pathogens or insects have caused big damage to forests and can completely transform them,” Metz said.
Metz also gave insight on why firewood quarantines have been instituted in many Oregon counties to stop the spread of the emerald ash borer.
“Often that’s to make sure that plant material from ash or whatever isn’t moved out or in because we might be inadvertently sending the eggs or the larvae or something that’s really hard to detect,” Metz said.
Ash trees, similar to other tree species, are an important part of the ecology in their habitats. Many native moth and butterfly species rely on ash trees as a place to lay their eggs, and their seeds are an important food source for birds and small mammals. The loss of the ash tree in any habitat, including in Oregon, would have a profound impact on the forest ecosystem and the species that rely on them as shelter and food sources.
“We want to give those other parts of Oregon as much time as possible to prepare, and so if we can limit the movement of green waste and firewood, we strongly, strongly encourage that,” said Cody Holthouse, pest prevention manager for the ODA in a statement for Oregon Public Broadcasting.
Though there are certain treatments that can be injected directly into ash trees to prevent the emerald ash borer from fully infecting them, forestry officials say that the best thing that can be done is for communities to be aware of the beetle and to prepare for when it inevitably enters their neighborhood forests.
Students can do their part to help stem the spread. According to environmental experts, the quarantine guidelines should be strictly adhered to: avoid moving firewood more than 10 miles away from where it was collected and immediately report suspected emerald ash borer infestations at the oregoninvasivehotline.org website or by calling 1-866-INVADER.
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