Foreigners. They come over here, take our jobs, make delicious burritos. Now their insects are killing our trees. And nowhere is the problem worse than in Griffith Park.

The polyphagous shot hole borer is a tiny (between .05 and .1 inches long!) beetle that arrived in the United States from Vietnam about six or seven years ago. The goldspotted oak borer came up from Mexico, through the Southwest to Southern California. Together, they are decimating the trees of Griffith Park.

Actually, the problem may be quite a bit worse than that, since the word “decimate” technically means to kill one out of 10 of something. Steve Dunlap, a supervisor at the Department of Recreation and Parks Forestry Division, estimates that as many as 20 percent of Griffith Park's trees could be killed as a result of the two foreign pests, although he admits there's no way of really knowing just how bad the carnage will be. Especially vulnerable are the sycamore trees, many of which have already died and have been hauled away.

“We have some that have died and have already been removed, and some that have been infected,” Dunlap says. “I can’t give you an exact number. Probably in the next year to five years, we will lose a significant amount of our sycamores and other trees.”

Rec and Parks' Tracy James says she expects the park to lose 92 percent of its sycamores within just a couple of years. 

Close-up of a dying Sycamore tree; Credit: Tracy James

Close-up of a dying Sycamore tree; Credit: Tracy James

So far there is no cure or treatment for the trees once the pests have gotten into them. The polyphagous, in particular, is seen by biologists as a kind of biological supervillain.

“It’s such a smart little beetle,” says Richard Hayden, head gardener at the Natural History Museum. “It reproduces in the tree and hardly ever comes out. It’s not the beetle doing damage, it’s the fungus the beetle carries, which interrupts the tree's ability to take in water and food.”

Hayden says that there are currently researchers in Vietnam looking for biological methods to stop the polyphagous. So far, all chemical treatments have been useless, because of the way the beetle stays inside the tree.

“Once the tree has been infected, it’s pretty much a done deal,” Dunlap says. “It’s just a matter of time. What makes it even more devastating, due to the nature of the insects, [is that] the trees become very brittle and start breaking apart, losing limbs. It makes it a pretty hazardous situation.”

The only thing the city can do now is replant the park with new trees, ones that will hopefully be less susceptible to pests. In the last few months, the Department of Recreation and Parks has planted more than 300 trees in Griffith Park.

As the Los Angeles Times reported in April, the polyphagous shot hole borer beetle “could kill as many as 27 million trees in Los Angeles, Orange, Riverside and San Bernardino counties, including parts of the desert. That’s roughly 38% of the 71 million trees in the 4,244-square-mile urban region with a population of about 20 million people.”

Sycamore trees are among the most vulnerable, but so are oak trees and avocado trees.

Though many avocado trees were attacked by the polyphagous, few of them were actually killed. Tom Bellamore, president of the California Avocado Commission, says: “It’s proven to be less of a problem for avocados then we initially thought. But we’re on our guard, for sure.”

The California avocado growers, he says, have spent around a million dollars researching ways to combat the polyphagous, but so far they haven't come up with a way to eradicate it or treat trees suffering from it.

“We’ve learned a lot about it,” Bellamore says, “but there’s still unanswered questions.”

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