Pest killing many of the oaks in Inland Empire's Oak Glen

OAK GLEN, Calif. (KABC) -- Pests are causing devastation to trees across California.

And that includes an area of the Inland Empire named after its centuries-old oaks.

The day after Christmas, Oak Glen was packed with people driving up to the 4,700 foot level - not only for the apples, but to take in the incredible scenery, punctuated by majestic oak trees. Many of them are more than 100 years old.

Arborist Doug Chudy with the Wildlands Conservancy says more than half the trees in Oak Glen are oaks.

But look closely and you'll a find a little pest that threatens their very existence: the goldspotted oak borer.

He says it's already killed at least 20 trees since they discovered it a few weeks ago.

"It's heartbreaking, to know these trees, especially the bigger, larger diameter trees that are so majestic are going to die in your lifetime," Chudy said. "It's inevitable. A tree has a life and time, but it's hard to say goodbye to them, especially so many that are so well-established."

Chudy thinks this pest got here by way of firewood - specifically, people bringing in firewood from places already invested with the beetles.

For example, Idyllwild has been dealing with this pest since 2012. He says the pests don't wipe out every tree - but can destroy half of them in a region.

So what's their plan of action? They'll probably have to remove all of the trees that have been killed by this pest, and that could be very expensive.

Beyond that, they only hope that people get the message not to bring firewood up here from outside the area.