By Zev Blumenfeld
They are tiny, cluster in groups and hang out on oak trees…and, no, they aren’t acorns.
The goldspotted oak borer (GSOB, Agrilus auroguttatus) – a six-legged, oblong-shaped invasive beetle – appeared in Big Bear in August 2019.
While no sightings of the GSOB have occurred in the Crestline, Lake Arrowhead and Running Springs communities, local groups like the Mountain Rim Fire Safe Council, which aims to educate and provide information on wildfire preparedness and prevention, are vigilant of its arrival.
The group’s president, Laura Dyberg, voiced her concern about potential forest destruction in the Rim communities should residents and visitors fail to take the proper precautions.
But how does a goldspotted oak borer relate to wildfires?
To answer this question, it is appropriate to look at an insect native to the San Bernardino National Forest — the bark beetle.
In 2003, California experienced a drought causing pine trees to compete for water. Lacking proper hydration and nutrients, the defense systems of these pine trees were weakened. The bark beetle fed upon the enfeebled trees, decimating forests and pines on mountain properties. Later that October, these dead and dying trees helped fuel the Old Fire, a blaze that caused community-wide evacuations and ripped through over 91,000 acres.
Much like the bark beetle, a future GSOB infestation would weaken and kill trees. “Flashy” fuels, such as weeds and grasses, could become kindling for bigger trees much the way twigs are used to help start a log campfire.
“Grasses that lead to the bushes, that lead to the smaller trees, that lead to bigger trees, ultimately build a fire that is so hot and powerful it ‘ladders’ the flames to the higher part of the tree,” Dyberg said. “If you’ve got a 100-foot tall or 75-foot tall oak that’s dead with no moisture, it becomes a torch.”
The overcrowding of trees in the San Bernardino Mountains creates an environment where trees must compete for resources, such as water. In a drought season, trees like the Canyon Live Oak, Coast Live Oak and California Black Oak will weaken without proper hydration, making them particularly susceptible to GSOB attack.
Native to Arizona, the borer was first identified in San Diego County in 2004. Dyberg said the beetle’s proliferation through Southern California has been almost exclusively contributed by infested firewood.
The fire safe council is addressing the GSOB threat through their campaign, appropriately named “Is There a Killer Lurking in Your Firewood?” The campaign functions on two levels — prevention and identification.
The council implores anybody purchasing oak firewood to find out its origin. According to the U.S. Forest Service, the borer has been found in San Diego County, Orange County, Wrightwood and Big Bear. Purchasing oak firewood from these areas should be avoided.
“Wood was moved by campers coming into National Forest areas or people buying the wood where they lived and bringing it to the (Rim communities). That’s the primary mode of transportation for the GSOB,” Dyberg said.
“Knowing the provenance of the firewood is really important.”
Dyberg also recommended buying debarked firewood.
“If the bark is removed, you can be pretty confident that the beetles are gone,” she continued.
GSOB identification is the second part of the campaign.
Dyberg said the borer prefers feasting upon older trees because the thicker bark provides more protection.
“The beetle will land on the tree and lay eggs on the tree,” Dyberg said. “The larvae will bore into the tree, going under the bark, and then they will populate and propagate for a few generations. When the beetles mature, and they’re ready to leave the tree, they cut out a perfect, flat on one side, D-shaped exit hole.”
These D-shaped exit holes, the size of a pencil tip, are located on the trunk of the tree and indicate the borer’s presence. Additionally, property owners may order GSOB identification kits through the fire council’s website.
Despite methods of identification, experts have yet to develop a treatment to save infested trees; however, Dyberg mentioned topical treatments and sprays might become a possibility.
The fire safe council is working with local legislatures to create legislation requiring the debarking of firewood before transport and sale. But enforcement is problematic — which agency will enforce such legislation, the method of enforcement and an appropriate penalty remain unsettled.
In preparation for the 2020 fire season and the GSOB, the fire safe council recommends property owners space trees at least an arm span apart.
Defensible space guidelines are available on the Mountain Rim Fire Safe Council’s website.
Dyberg said she understands the ambivalence property owners might express when deciding whether to cut down a healthy tree. The fire safe council will be applying for grants to ease the financial burden property owners may experience when clearing hazardous but healthy trees.
“Getting people to consider the spacing issue is a challenge, especially if it may not be in their budget,” Dyberg said. “I love my tree, it’s healthy, you want me to cut it down, and I don’t have any money. What part of that is going to make it work? Providing a financial incentive will go a long way in helping us make the forest healthier for all of us.”
For more information about the GSOB, defensible space and the Mountain Rim Fire Safe Council, visit www.mountainrimfsc.org.