Emerald ash borers spread, Mediterranean oak borers found in northern Oregon.

2025 IN REVIEW: Emerald ash borers spread, Mediterranean oak borers found in northern Oregon Published 4:00 am Thursday, January 1, 2026 By Lauren Bishop facebook sharing button email sharing button print sharing button 1/3 The infamous invasive emerald ash borer poses a significant threat to trees statewide. (Courtesy photo) Two bugs not native to Oregon made headlines in the northern part of the state as infestations were detected. Since first discovered in 2022, more emerald ash borers were detected in the Portland metro area and Yamhill County. Additionally, a new pest entered the ecological landscape: the Mediterranean ash borer. In September, the Oregon Department of Forestry found new infestations of emerald ash borers in Clackamas, Washington and Yamhill counties. Marion County also remains under quarantine to slow the spread of an early arrival of emerald ash borers. Trending Oregon State football adds four more coaches at December’s end Hillsboro police identify suspect arrested in Saturday homicide Native to eastern Asia, the pests might be a half-inch long, but they’re a huge threat. Emerald ash borer larvae tunnel into trees and munch on the inner bark, disrupting a tree’s ability to transport water and nutrients. A tree typically dies within two to five years of an infestation. Officials first detected emerald ash borer in Oregon in 2022 when they showed up in ash trees at Forest Grove’s Joseph Gale Elementary School. Since then, Washington County has been under a quarantine prohibiting the removal of ash, olive and white fringe trees — and related tree materials — to slow the pest’s spread. “The pattern of spread in the eastern U.S. has been that populations at first increase slowly and the rate of natural spread is slow,” Cody Holthouse, manager of the Oregon Department of Agriculture’s Insect Pest Prevention and Management Program said in September. “But within a few years there is a rapid build-up in the population and it spreads in all directions at a faster pace. That’s exactly what we’re starting to see with these detections.” Battling the beetle Local governments have been bracing for the spread since the initial detection. The city of Beaverton attempted to protect nearly 500 ash street trees by injecting them with an insecticide that helps prevent infestation while remaining safe for humans, pets and wildlife. Hillsboro also treated around 500 public ash trees along the city’s western and southern boundaries — while conducting a tree inventory of public and right-of-way trees to locate ash populations and shape response plans. Trees were removed in Woodburn’s Wyffels Park in October to attempt to slow the scourge. In addition to tree removals, the city’s response plan to slow the invasive emerald ash borer includes expanded partnerships, educational outreach and continued grant applications. Another borer detected in 2025 Trending 2025 IN REVIEW: Forest Grove voters turn down police building bond Five takeaways from No. 5 Oregon’s Orange Bowl win vs. No. 4 Texas Tech A second threat to some hardwood trees also raised its ugly head in northwest Oregon. This fall, the Mediterranean oak borer appeared in trees in at least six counties — Clackamas, Marion, Multnomah, Polk, Washington and Yamhill. The tiny insect typically infests Oregon white oaks, oftentimes with devastating effect as the tiny beetles carry a fungus that can infect a tree’s vascular system and lead to the tree’s death. In response, state foresters began setting traps throughout the Willamette Valley and beyond in an attempt to determine how widespread the borer infestation had become. The results of the study were daunting: More than 500 borers turned up in roughly 30 traps between Portland and Salem. Thirty-eight of the 944 oak trees inspected since the beetle was first detected in Oregon were found to be infested. Another 22 thought to be infested have been removed as well. Scientists playing catchup Since the outbreak, scientists are playing catchup, trying to learn what they can about the borers and the fungus they carry. “We still have a lot of questions about MOB that we’re working to find answers to,” said forest entomologist Christine Buhl, who leads the Oregon Department of Forestry’s efforts. “One basic question is what other tree species potentially could be affected by MOB.” So far in Oregon, Christine Buhl, who leads the Oregon Department of Forestry’s efforts, said only white oaks have become infested. California, on the other hand, has not been so lucky as two oak species have been attacked and killed by the pest, and Mediterranean oak borers have been found in other oak and even some non-oak species of trees. Fortunately, many oak trees that neighbor infested trees have shown no signs of infestation or decline. Buhl stressed that more research is needed to find out what level of resistance oaks might have to the fungus carried by Mediterranean oak borers. “My hope is there might not be widespread, rapid die-off of Oregon white oaks, like there is with emerald ash borer, which is killing most ash trees across the country,” she said. What you can do If you think you’ve seen an emerald ash borer or Mediterranean oak borer, the state departments ask that you first make sure it’s not a common look-alike bug. People who suspect they have found the beetles should report it by phone to 1-866-INVADER or online at tinyurl.com/yz8ys92t. To learn more about invasive species or report a potential pest, visit oregoninvasiveshotline.org. Reporters Gary Allen, Nick LaMora and Sophia Cossette contributed to this story. facebook sharing button email sharing button print sharing button You Might Like Elections USPS says mail-in ballots might not get postmark on same day they’re dropped off News

Read more at: https://forestgrovenewstimes.com/2026/01/01/2025-in-review-emerald-ash-borers-spread-mediterranean-oak-borers-found-in-northern-oregon/