By Mark Gutglueck
According to the United States Forest Service, there are unmistakable signs that both the Angeles National Forest and the San Bernardino National Forest within San Bernardino County are being threatened by the goldspotted oak borer.
The first time forestry officials were alerted to the pest locally was in 2012 in the area of Idyllwild-Pine Cove, south of the San Bernardino County border with Riverside County, on private property. Since that time, the beetle is recognized to have appeared in at least three other places within either San Bernardino National Forest or the Angeles National Forest, all within San Bernardino County.
The goldspotted oak borer, known scientifically as agrilus auroguttatus, is an invasive beetle native to southeastern Arizona that can kill oaks native to California. In October, it was detected in recently-killed California black oak trees, quercus kelloggii, in the unincorporated San Bernardino County community of Wrightwood, very close to the boarder with Los Angeles County. One of the directors of the Wrightwood Fire Safe Council, who is familiar with the goldspotted oak borer, made the initial discovery in Wrightwood and reported the infestation to the California Department of Forestry and Fire Protection San Bernardino Unit forester. The presence of goldspotted oak borer was confirmed by a U.S. Forest Service entomologist who identified numerous goldspotted oak borer produced D-shaped exit holes on infested trees in the area.
The Wrightwood detection represented the third infestation found in San Bernardino County since the discovery of goldspotted oak borer in the Oak Glen area in the fall of 2018, and the subsequent discovery of goldspotted oak borer in the Sugarloaf area of Big Bear in the summer of 2019. The infestation in Oak Glen occurred on private property. Based on analysis by a Forest Service entomologist, the infestation may have been there for approximately ten years. An infestation was soon after found at the Oak Glen Conservation Camp #25, a California Division of Forestry and Fire Protection facility on Forest Service land under permit. The infestation in the Sugarloaf and Moonridge neighborhoods in the Big Bear area existed on private property. Based on an analysis by a Forest Service entomologist, the infestation may have been there for at least five years.
As with the two previous infestations in San Bernardino County, it is believed this goldspotted oak borer infestation in Wrightwood resulted from goldspotted oak borer-infested oak firewood being brought into Wrightwood. Officials are urging the public to take critical precautions to avoid transporting infested oak firewood to other uninfested areas.
Locally, the U.S. Forest Service’s state and private forest health protection division is assisting a diverse group of land managers on a response to the infestation beyond Forest Service lands. Some of the participants include the local fire safe councils, the counties of San Bernardino and Riverside, the California Division of Forestry and Fire Protection, University of California Extension, the Inland Empire Resource Conservation District and the United States Department of Agriculture’s Natural Resources Conservation Service.
According to the Forest Service, “Any community or area that has coast live oaks (quercus agrifolia), California black oaks or canyon live oaks (quercus chrysolepis) is vulnerable to gold spotted oak borer infestation. Communities with significant oak populations include the San Bernardino mountain communities and surrounding national forest lands.”
The infestation is spread in two ways, according to the Forest Service. One is through natural spread. The beetles can fly short distances and spread slowly from tree to tree. There is also what is dubbed unnatural spread in which the beetles are moved long distances when humans move firewood and cause what’s called a satellite infestation. The Idyllwild, Oak Glen, Big Bear and Wrightwood infestations are believed to be manifestations of unnatural spread.
U.S. Forest Service Spokesman Zachary Behrens told the Sentinel, “Since firewood movement spreads the invasive insect, we continue to ask homeowners and campers to buy firewood locally.”
According to California’s Firewood Task Force, “Our forests are threatened by nonnative insects and diseases. Many of these pests can be transported long distances on firewood. Once transported to new areas, these invasive species can become established and kill large numbers of trees and shrubs.”
The California Division of Forestry advises that residents or visitors to the forest “buy it where you burn it” when it comes to firewood.
The firewood scout webside – http://firewoodscout.org/s/CA/ – provides information on where firewood can be found or purchased locally. If firewood is to be purchased from dealers remotely located from where the firewood is to be used, it is advisable to obtain heat-treated firewood. Heat-treated firewood is preferred, as heat treating eliminates live pests which could be transported in or on firewood. If heat-treated firewood is not available, the next best alternative is firewood that has been cured or seasoned for at least two years, lowering the risk for some – although not all – pests.
According to the California Division of Forestry, “If the firewood has not been heat-treated, be sure it was cut locally and don’t move it out of the area. Firewood that is not heat treated may have pests and diseases that should not be transported to new locations. If the wood is not from a local source, you should consider finding a new firewood vendor selling local or heat-treated wood.”
Golden Spotted Oak Borer Infesting County’s Forests
By Mark Gutglueck