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Goldspotted Oak Borer

Goldspotted Oak Borer (GSOB) (Coleoptera: Buprestidae), is a flatheaded borer beetle new to California that poses a significant threat to oak trees. The pest is native to southeastern Arizona, where it is found in oak woodlands.  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 saving trees once a major infestation occurs, although management and damage mitigation is possible in low-level infestations.

Source: Goldspotted Oak Borer Field Identification Guide (University of California IPM, January 2011)


Visit these links to learn more about Southern California GSOB research, identification, tracking, management options, and more:



Our RCD team currently supports two GSOB management and research projects.

We support research and a capacity building demonstration project in collaboration with  La Jolla Band of Luiseño Indians.  This project has many facets including felling and processing dead oak trees,  planning,  researching new treatments, and workforce development- to name a few. Joelene Tamm, a Native American researcher, is collecting data to  observe how cultural burning can be used as a treatment tool to combat GSOB to save heritage oak trees. 

Learn more about her research  HERE.


Additonally, we support the Oak Grove GSOB Project  in collaboration with researcher Dr. Tom Scott of University of California Agriculture and Natural Resources (UCANR), and  state-licensed and county-registered pesticide applicator and arborist Green Tree Forest Service.  This demonstration project supports annual monitoring and treatment of hundreds of trees as part of a 10-year research project. This video shows thier developed method of treatment. 


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