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About Goldspotted Oak Borer

Dead Oak
The goldspotted oak borer (GSOB), Agrilus auroguttatus (Coleoptera: Buprestidae), is a flatheaded borer new to California that poses a significant threat to oak trees. The pest is native to southeastern Arizona, although a related species occurs in southern Mexico and northern Guatemala. GSOB was first collected and identified in California in 2004 in San Diego County but was not linked to extensive oak mortality until 2008. As of 2010, GSOB has killed an estimated 21,500 trees covering 1,893 square miles in San Diego County in forests, parks, and residential landscapes.

GSOB larvae feed beneath the bark of certain oaks near the interface of the phloem and xylem, the nutrient and water conducting tissues of plants. The larvae damage both of these tissues as well as the cambium, a unicellular layer between the phloem and xylem that is responsible for the radial growth of the tree. Trees die after several years of injury inflicted by multiple generations of the beetle, causing significant economic, ecological, cultural, and aesthetic losses to the region. GSOB poses a major threat to susceptible oak species throughout California and southern Oregon. Currently there are no effective tools for protecting trees once infestation occurs.

Source: Goldspotted Oak Borer Field Identification Guide
            University of California IPM, Jan. 2011

Read more about the goldspotted oak borer situation in the GSOB Issue Paper.

Table of Contents


Learn how to identify GSOB adults, larvae, and oak damage.


See a map of discovered goldspotted oak borer infestation areas in San Diego County.

Host Oaks

Find out what we know about the oaks being attacked by GSOB.

Pest Impact

The impact of GSOB infestations affect regional oak tree populations, contributing to their death. Get more information about what else is affected by this pest.


We have provided answers to some of the most frequently asked questions concerning GSOB.

GSOB Management Story Map

View an interactive Storymap outlining GSOB distribution, management guidelines, preventative treatment strategies and more!


Resources to help you evaluate oak tree health and diagnose goldspotted oak borer infestation. Sampling information and reporting options are offered as well.

Management Options

Brief discussions and resources regarding regarding community preparedness, infested live trees, chemical control and other management options.


For information on why you shouldn't move oak firewood, availability, management practices, and additional information on GSOB and firewood.

Related Images

Launch Image Gallery: Larger GSOB Images 


History of GSOB in California

GSOB has been documented since the late 1800s. This is apparent from museum records from southeastern Arizona, southern Mexico, and northern Guatemala (MAP). Collection dates for adult museum specimen ranged from May through September. GSOB was first collected in California in 2004. In southern California, GSOB currently occurs in a roughly 31- by 25-mile area of east San Diego County.

Oak damage associated with GSOB was first confirmed in the County of San Diego in 2008. However, elevated levels of oak mortality have been mapped aerially on and around the Cleveland National Forest since 2002.

At present, there are no reports linking GSOB to damage in oaks outside of California. Although some have attributed its presence in southern California to range expansion from its native populations to the east and south, but reports suggest that GSOB may have been introduced during the last ten years on oak firewood brought in from Mexico.