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Oak-Killing Beetle Found In San Bernardino County


An invasive species of oak-killing beetles has been found in the unincorporated San Bernardino community of Sugarloaf.

The goldspotted oak borer, or GSOB, is a species of beetle native to Arizona that’s found its way to California.

It’s been found in San Diego, Riverside, Orange and Los Angeles Counties. It was first found in San Bernardino County when it was discovered in Oak Glen in 2018.

Forest Service officials announced earlier this month that GSOB had been detected in Sugarloaf. It was most likely brought there through infested firewood.

Kim Corella is a Forest Health Specialist with Cal Fire. She says homeowners with oak trees should look for a few tell-tale signs of GSOB infestation.

Corella: “So the symptoms homeowners should look for would be staining on the trunk or the bowl, they'll see these d-shaped exit holes, they'll see some woodpecker feeding, they like to flick off the bark and eat the larvae beneath the bark, and then they might see some crown die-back.”

Corella says if you think your oak trees may be infested with GSOB, you should go online to report it and have it diagnosed.

Corella: “So there's a website, it's www.gsob.org. If you go on there, there's a lot of information and there's a reporting tool. And it goes through the steps of what you're seeing, confirming that it is GSOB, you fill out all that information, you want to take two or three pictures, one picture of the whole tree focused so you can see it, and then one picture of the exit holes. What you're seeing on the trunk of the tree and that that's in focus as well. And then attach those to that report, and then send it in and it'll get sent to a database where it's read by Cal Fire personnel and Southern California and then the closest person that knows how to identify GSOB will come out and contact you and look at your tree and then will diagnose it.”

Corella said GSOB could be lurking in other parts of San Bernardino County.

Corella: “Yes, definitely, I believe so, yes. Firewood is the movement of where this insect spreads and infested firewood could be moved unknowingly by a homeowner into a new home, into their house for heating and they don't know they have it, and so yeah, it definitely could be in other places in San Bernardino County that we just don't know. So people should be on the lookout for this insect, check their trees and see if they see any of these exit holes or staining or crown die-back. And then if they do, report that on the tool on gsob.org.”

Corella says that GSOB, if left unchecked, could pose a threat to a large number of oak trees in San Bernardino County. But she says aggressive treatment can limit its spread.

Corella: “It's definitely in the area and if they do management very proactively then they can minimize the spread, but if management's not done in an appropriate amount of time, then this insect can spread and it builds up population levels and then it can increase and kill more trees. So aggressive management is the way you want to go to try to keep this insect under control. Probably not going to eradicate it, but you can keep it under control with aggressive management and examples of that are Idyllwild and Green Valley and even Oak Glen area, they've aggressively treated their trees and managed them and that population hasn't spread as fast as it has in other areas.”

You can learn more about the goldspotted oak borer at gsob.org.

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