Frequently Asked Questions

Where is the current infestation of the goldspotted oak borer located?

While the original infestation of goldspotted oak borer is centered around Cuyamaca Rancho State Park and the Descanso Ranger District of Cleveland National Forest in San Diego County, satellite infestations have emerged in Riverside, Orange, Los Angeles, and San Bernardino Counties. See Distribution for more details and maps.

How can I save my trees from the goldspotted oak borer?

Lightly infested trees (<25 D-shaped exit holes) and high-value trees can be chemically treated according to management guidelines. Severely infested trees (>120 D-shaped exit holes) are likely beyond saving, as GSOB damage is irreversible once beetles have emerged. Severely infested trees may serve as "amplifier trees," which increase the likelihood of other trees being infested, so they should be removed and the wood should be treated according to management guidelines.

Preventive treatments can also be conducted on large trees (trunk diameter >8 inches) in an infested stand that have not already sustained damage. The best prevention is yearly monitoring on large oaks for exit holes and rapid treatment and management when GSOB is detected.

Where did this beetle come from, and how did it get here?

GSOB is native to the oak woodlands of southeastern Arizona. It was first collected in southern California in 2004 during a CDFA exotic woodborer survey, but has likely been in the area since the late 1990’s. Researchers believe that GSOB was introduced into southern California on transported firewood.

What trees does the goldspotted oak borer attack and kill?

The goldspotted oak borer can attack and kill coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), and canyon live oak (Quercus chrysolepis). This beetle is only currently known to feed on oak tree species. No other oak species have recorded infestations and deaths comparable to the three known host species.

What are the symptoms of injury from the goldspotted oak borer?

D-shaped adult exit holes on the main stem, dark black or red staining on the trunk and larger branches, and crown thinning and canopy die-back are all signs of injury from the goldspotted oak borer.

How fast is this beetle spreading?

While GSOB are strong fliers and can travel up to 10 miles at once, they commonly stay near their host trees and rarely travel great distances. All satellite infestations (in California counties other than San Diego County) were likely caused by the transport of infested firewood. Buy it where you burn it to stop the spread!