This is KPBS Midday Edition. I'm Maureen Cavanaugh. The state board of forestry is sponsoring an unusual tour in San Diego today. It will focus on areas of massive tree die off caused by insect infestation. Invasive beetles like the goldspotted oak borer have killed tens of thousands of oak trees in San Diego County since they were first discovered more than 10 years ago. The beetles are originally from Arizona, but have continued their creep northward in California. Earlier I spoke with Matt Dias. Acting executive officer of the California Board of Forestry and Fire Protection. Welcome to the show. Earlier this year, the board of forestry said San Diego is considered generally infested by invasive beetle species. Speaking about the goldspotted oak borer , how much of San Diego is infested? In 2016 the board did expand the zone of infestation for the goldspotted oak borer. Currently, it's thought to be about 100,000 acres of the county that's infected. How to the spread? It spread through dissemination of firewood. Any individual that's purchasing firewood should focus on purchasing from within their localized region. If you purchase firewood from an infected area and disseminate that to an area that is not currently infected, these beetles are propagating in that firewood and will spread to uninfected areas. Firewood is the main court -- culprit. I've read even if the firewood is dry or doesn't look like it has insects, it can still be a problem. Yes. To the common person, and infected piece of firewood but that no different than a normal one. They are very small holes. These are very small insects. The entrance and exits from a piece of firewood would look like a very tiny hole to the common eye. You would never know. It's estimated that 80,000 oak trees have been killed by these beetles over the last 10 years. Can you tell us how does that kind of tree die off? We are concerned with the three species, Canyon Live Oak, California black oak and coast Live Oak. That's the species that are present. When these trees are being lost, you are losing the entire oak Woodland. We've had, it's know that there are spans of oaks that of lost 90% of the trees. Of vegetation type change. It's not a couple of trees here are there, what was once present will no longer be. All the habitat changes because of that? Yes oak woodlands are known to be diverse in terms of wildlife, food product produced from the trees, wildlife habitat and the species of those that depend on oak woodlands. What's the connection between a tree susceptibility to an insect and the drought? The relationship is trees rely upon water to produce up which allows them to push out beetles that are infecting them. When water resources become limited, the trees can no longer produce the sap needed. Therefore the beetle population explodes. That's what has happened over the last four or five years. You are with the state board of forestry, you are not only concerned about the goldspotted Oak borer, there are a couple other infestations that are hurting trees in San Diego County. Can you tell us about those? The other two that are also non-native are the Kuroshio shot hole borer and the poly for us shot hole borer. They are from Taiwan or Vietnam, they come in on pallets. They are very small species that affect an entire host of tree species. The Tijuana River Valley, you will notice every single Willow tree along the river has died over the course about of -- a year at a half. Every single Willow tree has died within that Park. When you are talking about the goldspotted oak borer, these beetles have been here in San Diego County for at least a decade. Does this continued spread mean that the prevention methods that the state has been trying to put forward are not effective enough to keep the beetles and check? It's important to realize that this issue did not reside -- does not reside in California holy -- holy. It's not an epidemic that's attacking only our state, they came from Arizona. Prevention measures implemented are expensive and the effectiveness isn't very well-known. There's a lot of research that is ongoing. I think the prevention measures are going to be helpful. I can't make any claims to the fact that they will stop the spread. What needs to happen, people need to raise awareness, we need to raise the education level and people need to understand that firewood is not as simple as a campfire and a warming fire in your home. It really can cause troubles to the resources of the state of California. I've been speaking with Matt Dias acting executive officer of the California Board of Forestry and Fire Protection. Thank you very much. Thank you.
State forestry officials are leading a tour Wednesday across San Diego County, observing parks and campgrounds devastated by invasive beetles. One species, the goldspotted oak borer, has infested more than 100,000 acres across the county.
That species originated from Arizona and was brought to Southern California by infected firewood, according to Matt Dias, acting executive officer for the California Board of Forestry and Fire Protection.
Infected and healthy wood are indistinguishable to the untrained eye, Dias said, so he cautions campers to buy firewood locally to help curb the beetles’ spread. In February, the forestry board said Los Padres National Forest, which stretches from Ventura to Monterey Counties, is considered at risk.
Trees can be especially vulnerable to beetle infestations during drought conditions, Dias said.
“Trees rely upon water to produce sap, which allows them to push out beetles that are infecting them,” he said. “But when water resources become limited, the trees can no longer produce the sap necessary to push the beetles out and therefore the beetle populations explode and that’s what has happened over the course of the last four or five years.”
While the goldspotted oak borer is the most prevalent invasive beetle in San Diego now, other species might not be far behind. The Kuroshio shot hole borer has devastated the Tijuana River Valley, according to Dias.
“If you take a trip to the regional park in the Tijuana River Valley, you will notice that nearly every single willow tree along the Tijuana River has died over the course of about a year and a half’s period,” Dias said. “That’s due directly to the Kuroshio shot hole borer.”
