Gearing up to stop oak borer spread

Since discovery of the invasive and dangerous Goldspotted oak borer in Idyllwild two weeks ago, scientists and professional responders from CAL FIRE and the Forest Service have been meeting to devise steps to contain the spread of the destructive beetle.

Kevin Turner, Goldspotted oak borer coordinator at the University of California, Riverside, said the next step is to work with the Forest Service to get an aerial survey of the Idyllwild area to map distribution of California black oak, the local oak Turner said is most susceptible to the beetle. “We’re hoping to identify and map black oak distribution on both public and private land in the Idyllwild area,” Turner said.

“We’ve already done a ‘windshield survey’ of the Idyllwild area, checking trees to see if any have shown the same symptoms of early leaf shriveling and die off that characterized the infected tree recently removed on Highway 243.” Those involved included Turner, Forest Service lead entomologist Dr. Tom Coleman, CAL FIRE Division Chief Kathleen Edwards and UCR’s Dr. Tom Scott. “We did not find any that were similar,” said Turner. He also noted that there will be little movement of larvae during the winter months, and that symptoms of infection would not likely be seen until the arrival of warm weather next year. “We’ve surveyed areas around the infected tree, over where the Woodies cut wood (Idyllwild HELP Center), the County Park and South Circle,” Turner said. “I’ve been up there a lot and I saw nothing obvious that matched the same symptoms.”

Turner requested that private landowners with black oaks on their property report any symptoms that might be indicative of infestation. Again, those include early browning or shrinking of leaves, canopy thinning, and “D” shaped exit holes in the oak bark. Also, if people have firewood they suspect came from infected areas of San Diego County, they should call Turner’s office for someone to come out to inspect it. The number to call is (951) 827-2973.

If property owners suspect their trees are infected, Turner said someone from his working group would come out to check. “We can go back with the property owner’s permission, peel back the bark and look for [oak borer] larvae.”

Scott and Turner met with community members, including the Garden Club and master gardeners and staff at the Nature Center on Tuesday, Nov. 20, as part of a citizen outreach. Scott presented a slide show and explanation of how the beetle infects a tree, the life cycle within the tree and how quickly tree die-off can occur.

He explained that entry is no higher than 30 feet from the ground with most around 10 feet. “The heaviest time of mortality is during times of drought,” said Scott. “Trees with thicker bark are attacked more frequently. And with infected large trees, there is a 90 to 95 percent mortality. What we’ve seen in San Diego County is 80 to 95 percent death, in outbreak mode, within six to eight years after infection.”

The news Scott delivered was sobering given what has already happened in San Diego County. Turner said he and Scott were encouraged to see a large turnout of around 35 people, since locals, here each day, can contribute very helpful information by observing local black oaks.

The Garden Club distributed flyers at the Tree Lighting Ceremony requesting that anyone who has purchased oak firewood from a supplier south of Idyllwild in the last three years, who has noticed any oak trees that are not as robust as they had been and are different in appearance from similar and nearby black oaks, and who knows of anyone importing wood to the Hill from an outside source to call Turner’s office at (951) 827-2973.

Third District Supervisor Jeff Stone has also requested that any roadside wood sellers be reported to his office at (951) 698-7326. Roadside vending is illegal in Riverside County.

Why should local property owners be worried? The cost to bring down an infected oak could run from $700 to $10,000 depending on tree size and proximity to structures. Property values and habitat would also be diminished by loss of Hill black oak. “This is an emergency,” Stone said.

Many states have firewood ordinances because of concern over invasive species damage. Those ordinances are strict and enforceable. Currently neither California nor Riverside County has any specific firewood ordinances that require source labeling and limit transportation.