After killing more than 200,000 oak trees, the Goldspotted Oak Borer is continuing to spread across California as state agencies issue renewed warnings.
The Goldspotted Oak Borer is an invasive beetle that targets and weakens oak species, with the affected trees largely gone unnoticed by the public.
🚨 California’s Most Wanted: Goldspotted Oak Borer 🚨
This tiny pest is responsible for killing more than 200,000 oak trees across California—and it’s still spreading.
The Goldspotted Oak Borer (GSOB) attacks black oaks, coast live oaks, and canyon live oaks, cutting off the… pic.twitter.com/NsMrJktccS
— CAL FIRE (@CAL_FIRE) March 25, 2026
According to a recent CAL FIRE post, the pest has killed more than 200,000 oak trees across California and continues to spread. The beetle primarily affects coast live oak, canyon live oak, and California black oak, leading to widespread tree mortality.
This oak tree’s mortality affects the environment and even poses risks to human safety. The infestation has grown beyond San Diego County into Riverside, Orange, Los Angeles, San Bernardino, and Ventura counties, according to the University of California Agriculture and Natural Resources.
Damage begins beneath the bark, where larvae feed on the phloem and cambium layers. This disrupts the tree’s ability to transport water and nutrients, causing branch dieback and gradual decline.
Signs of Infestation
The University of California notes that infested trees often show visible signs of decline, including thinning canopies and small, D-shaped exit holes in the bark.
Bark staining, often appearing as dark or reddish sap patches, is another indicator. Trees may also show blistering bark, twig and branch dieback, and increased woodpecker activity as birds feed on larvae beneath the surface.
The Goldspotted Oak Borer (Agrilus auroguttatus) is an invasive beetle species affecting oak trees across California.
The beetle was first identified in San Diego County in 2004 and has since spread to several Southern California counties, according to California State Parks. It poses a significant threat to oak populations.
How To Control Infestation
The beetle’s spread is closely linked to human activity, particularly the transport of infested firewood. Larvae can survive in cut logs, allowing the pest to travel long distances.
Efforts to control the spread include firewood quarantines, monitoring programs, and public outreach initiatives to track infestations and limit further impact.
Recommended practices for handling infested wood include debarking, grinding, or chipping to eliminate larvae.
Avoiding the transport of untreated wood remains a key step in limiting further spread.
Officials encourage residents to buy or use firewood locally, avoid moving oak firewood out of infested areas, and report suspected infestations to authorities.
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