Goldspotted oak borer

The goldspotted oak borer is 10 mm in length with a black body and gold spots. It was originally found in San Diego in 2004 and spread to San Bernardino County, infesting oak trees.

The detection of an invasive beetle called the goldspotted oak borer in the mountain community of Sugarloaf near Big Bear is causing concern for communities such as Chino Hills which has thousands of oak trees, said city and state officials.

The beetle was found last week by the California Department of Forestry and Cal Fire underneath the bark of a California black oak on private property that contained dying and dead oaks, said Kim Corella of Cal Fire.

She said the beetle may be in other portions of the county but not yet discovered.

The non-native beetles aggressively attack California black oaks, coast live oaks, and canyon live oaks whether in mountain communities, forests, valleys, or cities, she said. 

“To make matters worse, the beetles prefer larger oaks, the very trees we depend on for beauty, shade, and wildlife habitat,” Ms. Corella said.

The beetle is native to Guatemala, southern Mexico, and southeastern Arizona, and was first collected in San Diego County in 2004, according to officials with the University of California Cooperative Extension.

It is the second infestation in San Bernardino County, with the first in the Oak Glen area in 2018, Ms. Corella said. An infestation also occurred in Idyllwild in 2012.

The pest has killed thousands of oaks in the Cleveland National Forest, said Mark Hoddle of the Department of Entomology at UC Riverside.

“The goldspotted oak borer poses an unprecedented threat to native oaks in southern California,” Dr. Hoddle said. “Hiking trails and campsites have been closed because of the risk of branches dropping from dead trees.”

Wood transport

Sean O’Connor, an arborist and operations and maintenance manager for the City of Chino Hills, said the beetle is a significant threat to Chino Hills and other cities in the region.

“There are nearly 4,000 oak trees in our parks, landscaping and parkways,” he said. “This number does not account for the many oak trees on private property and city open space.”

There are also thousands of coast live oaks in the nearby Chino Hills State Park, said Kelly Elliott, Inland Empire District Superintendent.

Mr. O’Connor said residents should not transport wood from dead oaks, to avoid spreading the pest.

Doug Yanega, also of UC Riverside’s Department of Entomology, said people should “never ever” transport wood from dead oaks, not even a few miles.

“It realistically should be treated like a quarantine situation,” he said. “All it takes is a few people who don’t know any better or think the rules don’t apply to them, to infest new areas.”

The Carbon Canyon Fire Safe Council has been promoting a public awareness campaign for several years about the threat of the beetle, said Danielle Barnes, fire marshal for the Chino Valley Fire District. 

The campaign, called “Buy It Where You Burn It” encourages individuals not to move firewood from locations where they are camping because infected firewood has been responsible for introducing the beetle to new areas, Ms. Barnes said.

Fire Safe Council member Ron Nadeau said Cal Fire has inspected stressed oaks in Chino Hills for signs of the beetle and nothing has been detected so far.

Mr. Nadeau said changing behavior in hauling firewood is not easy, but the Buy It Where You Burn It campaign is something everybody can do to slow the progress.

Trees attacked by the beetle show extensive bark staining that can appear as black regions or red blistering with sap oozing from under the bark.

To learn more about tree symptoms, visit the University of California Cooperative Extension website at www.gsob.org.

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