Nov 12, 2024UC ANR experts combat invasive beetle
Following the recent arrival of invasive shothole borers in the Bay Area, University of California Agriculture and Natural Resources (UC ANR) experts are helping local communities tap into Southern California’s experience to mitigate the pest’s impact. The beetles, detected in San Jose in late 2023, threaten urban forests, making early detection and expert coordination essential.
The invasive shothole borers (ISHB) have already devastated Southern California trees, with tens of thousands lost over the past decade, according to Beatriz Nobua-Behrmann, UC Cooperative Extension urban forestry and natural resources advisor for Los Angeles and Orange counties. In one year alone, 500 trees were removed in a single park, and some neighborhoods lost 90% of their trees. “That kind of impact happened in many locations,” Nobua-Behrmann said.
Due to the serious threat ISHB poses to California’s urban forests, UC ANR researchers have worked since 2012 on strategies to control the beetle. The team’s insights now assist Bay Area efforts to track and manage the pest. “The UC ANR team is comprised of subject-matter experts,” said Drew Raymond, interim agricultural commissioner for Santa Clara County. “They’ve transplanted all of the experience from Southern California to Northern California.”
UC ANR advisors Lucy Diekmann and Igor Lacan are leading workshops and trainings to equip Bay Area officials, land managers and arborists. According to San Jose city forester Sara Davis, this collaboration has enabled the city to establish a robust plan for identifying and managing infested trees. “Lucy and Igor have been instrumental in organizing our partners,” Davis said, emphasizing the critical role of the UC ANR network’s expertise.
The pest’s biology complicates management. The beetles live most of their lives inside trees and mate with siblings, rendering typical pest control tools, like pheromone traps, ineffective. “Their biology limits what we can do,” Nobua-Behrmann said, explaining that the beetles’ hidden nature often allows populations to grow unnoticed.
In Southern California, effective responses included early monitoring and public engagement. Nobua-Behrmann developed a community training program, teaching residents to identify the tiny entry holes that indicate ISHB infestation.
“It would be great to get this program going in Northern California,” she said, pointing to the power of public vigilance.
With ISHB cases clustered around San Jose’s Coyote Creek, experts stress timely intervention to prevent widespread damage.
“It’s also important to not move firewood and instead buy it where you will be burning,” Nobua-Behrmann said. “It’s one of the best things people can do to protect trees from invasive pests.”
After identifying and removing amplifier trees, land managers and landscape arborists should have a plan for replanting, Lacan added. He said they should prioritize species that are less susceptible to the beetle, using his Pest Vulnerability Matrix tool that lists the major pests for different mixes of trees.
“We need to figure out how to have sustainable urban forests, even with this pest,” he said. “We know we can do it, largely thanks to our colleagues in Southern California. So the key lesson is to replant soon – choose smartly, but replant right away.”
