A tiny insect, so small that six of them could fit on a penny, is threatening some of the most iconic trees in the Central and South Coasts.
The destructive goldspotted oak borer has been spreading in Southern California. Now, it's been found in Ventura County.
"It's a very scary pest for our beloved coast live oaks and black oaks here in California," said Beatriz Nobua-Behrmann, an ecologist who serves as Urban Forestry and Natural Resources Advisor with the University of California Extension. "The goldspotted oak borer is a beetle...from the group of jewel beetles. It's shiny and very beautiful. It has thick golden spots on its back. But, despite the fact that it's quite beautiful, it causes a lot of damage."
According to Nobua-Behrmann, they’re not native to California. They hail from Arizona.
"They came to California and started attacking the oaks here. The oaks in California are not adapted to being attacked by this beetle, and they can't defend themselves. As the beetles bore inside the tree, the larvae feed on what would be the vascular system of the tree, all the vessels with water and nutrients. That causes enough damage that the tree starts to decline, and eventually the tree dies."
They were first spotted in California in 2008, and since then, a string of infestations has slowly worked up the state, starting in San Diego County. They spread to Orange County, Riverside County, San Bernardino County, Los Angeles County, and now Ventura County.
It's estimated that the beetles have killed about 200,000 oak trees in the state.
The first find in Ventura County was in the Box Canyon area, in the eastern part of the county. Nobua-Behrmann said three infestations have been identified at this point, but the beetles haven't spread countywide.
Has it moved further up the coast, to Santa Barbara and San Luis Obispo Counties?
"Not that we know of," confirmed Nobua-Behrmann. "Fingers crossed."
Researchers did some detective work to figure out how the beetles are spreading. The most common way is by people unknowingly moving firewood infested with the beetles.
"It's most likely being moved by people who don't even know they are moving a pest with the," said Nobua-Behrmann.
She added that while predators like woodpeckers like eating the beetles, they can’t eat enough of them to stop the infestations.
Seriously infested trees need to be cut down and removed to prevent outbreaks from spreading. If caught early, pesticides can sometimes save a tree.
Nobua-Behrmann described how to spot an infested tree.
"The canopy is getting thinner, and the branches are wilted and dry. Those things are telling you something is going on with the tree. What you need to find is this D-shaped exit hole (it looks like a capital D) in the bark."
According to Nobua-Behrmann, the most effective tool is to isolate the outbreaks, which prevents the spread of infected firewood.
She said you should be wary of moving firewood. The best bet is to get heat-dried firewood, which is sold in stores. You can also use locally-sourced firewood.
What is potentially dangerous is bringing in backyard firewood from areas like Los Angeles and Orange Counties.
The researcher believes the spread of the destructive beetle can be stopped if the public cooperates and doesn’t move firewood infested with the insects.
