The Gold Spotted Oak Borer

What’s yellow and green and likes to bore into oak trees?  

 

Let me introduce to you the Gold Spotted Oak Borer (Agrilus auroguttaus) or better known as GSOB. GSOB is a beetle native to the South Eastern Arizona region, where its larvae feed on native oak trees by eating through the oak's cambium. GSOB isn't considered a pest in its native habitat but when it moved from Arizona to San Diego county California in the early 2000s it had a devastating impact on oak ecosystems of the southern California region. An intense infestation spread from San Diego County to Los Angeles County, where Los Angeles oak woodlands are now facing the same threat.

 

A GSOB infestation leads to a tremendous increase in oak fatality, as the larvae burrow through the tree’s vital vessels that transport sugars and water throughout the tree. Oak trees are essential to Southern California’s ecosystems as they have both cultural and ecological significance. 

 

Here is what you should know: GSOB prefers Canyon Live Oak, Black Oak, and Coast Live Oak trees; and have consistently been found in these oak trees in particular. A GSOB infested oak tree can cause bark staining, leaf loss, heavy woodpecker foraging and decaying branches. Up close on the trunk of the oak tree, you can identify GSOB by their iconic D-shaped exit hole that is 10 mm wide. If you spot a tree that doesn't look healthy or think you spot an exit hole, you can reach out UCANR by submitting this form . Experts will be able to confirm the presence of GSOB and advise on any actions.

 

Additionally, to reduce the spread of GSOB, follow the phrase, “buy it where you burn it”. This means buy firewood locally and burn it in the area you bought it from, as GSOB can be within the bark of your firewood. 

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Article by Kiara Bremner, GrizzlyCorp Fellow