FELTON >> An invasive beetle that poses a threat to the wooded abundance in the Santa Cruz Mountains was recently spotted in North Santa Cruz County, officials announced Wednesday.

The county Department of Agriculture and the UC Cooperative Extension shared in a release that they are monitoring a confirmed infestation of the nonnative invasive shothole borer beetle along a section of Zayante Creek, south of Graham Hill Road, after tree damage was spotted by a Felton resident while hiking in the area.

Brian Woodward, a forest adviser with the UC cooperative managing Santa Cruz, Santa Clara and San Mateo counties, told the Sentinel that the infestation was detected Oct. 4. Because it was early in the monitoring process, researchers don’t know exactly when the beetle arrived in the area, though there are indications it’s not a new occurrence.

“It’s probably been here for more than a year, potentially even longer than that,” said Woodward, “because a number of trees are infested and there’s a number of different burrowing holes that are present on many of the trees at the site as well.”

The diminutive pest, about the size of a sesame seed, drills tiny holes into a wide variety of trees and introduces a fungus that it then harvests as food for itself and its larvae. Nourishing as it might be for the beetle, the fungus is toxic for the tree, which responds by sealing the problem area off from the rest of its limbs, leading to branch dieback and, eventually, complete death of the tree itself.

Because the beetle is nonnative, it doesn’t have any natural predators in the region that can keep the population from exploding, making the creepy crawler a formidable arboreal adversary.

Another big part of the danger, according to the UC extension, is that the invasive beetle is known to kill a broad swath of otherwise healthy trees in the riparian corridor and urban areas. In all, there are 17 tree species that can be killed by the shothole borer beetle, Woodward noted, but the list does not include the redwood that is ubiquitous in the Santa Cruz Mountains. At-risk trees include the box elder, California sycamore, valley oak, Japanese maple and American sweet gum.

“The threat should definitely be taken seriously,” said Woodward, adding that it was too early in the surveying process to say how many trees in the area could be impacted.

Because the beetles are so small and live almost the entirety of their lives in their tree hosts, they are exceptionally difficult to spot, though a key sign of infestation includes small holes in trees that are perfectly round and are roughly the size of a ballpoint pen tip. Other signs may include wet staining, gumming, frass, boring dust and sugary buildup around the holes.

The hard-shelled bug is already well-established in Southern California, where it has killed tens of thousands of trees since it was discovered in the early 2000s, but it has begun spreading to other parts of the state — a list that now includes Santa Cruz and neighboring regions. The beetle was detected near Coyote Creek in San Jose in August, and while researchers were working to find out how widespread that infestation was, a release from Santa Clara County noted it was “likely too late to eradicate” the pest.

Though Woodward said his team will remain in monitoring phases for a while, management strategies that could eventually be implemented, depending on property owner willingness, could include removal of an “amplifier tree,” or the tree where the vast majority of the beetles are reproducing, as well as other chemical or fungicidal interventions.

To identify any new potential infestations, Santa Cruz County officials recommend taking UC extension’s invasive shothole borers detection assessment, available at ucanr.edu/sites/pshb. To report suspected damage from the beetle, property owners should call the Santa Cruz County Department of Agriculture at 831-763-8080.