Dear Fire Safe Councils:
I represent the Education and Outreach Subcommittee that is part of the Emerging Tree Pests working group currently focused in southern California. We are asking local Fire Safe Councils throughout California to help us educate their respective communities about the threat of some new, invasive, tree-killing pests. These pests are already a big problem in southern California, and they can quickly be spread elsewhere in the state through human transport of infested woody material. Please help us equip your community with information so it can be proactive in invasive pest prevention efforts, detection programs and rapid response planning.
Unlike native bark beetles which kill conifers primarily during times of extended drought, these non-nativeinvasive pests are successful killing trees in non-drought conditions. Instead of attacking weakened conifers, these invasive beetles are attacking seemingly healthy broadleaf tree species including oaks, sycamores, cottonwoods, maples, willows, and other forest, woodland, riparian and landscape trees. Their damage is not limited to forests, but includes woodlands, parks, wetlands and landscaped urbanized areas. The resulting dead and dying trees increase fire and falling hazards and result in esthetic, ecological and economic losses.
Unfortunately, there are no simple solutions for controlling these pests once they establish a new infestation. Typically, new infestations are not discovered or identified until after they have become well established making total eradication impossible. Although research is ongoing, to date, the use and effectiveness of pesticides is extremely limited and possible biological controls are in the far distant future.
Although these pests can spread on their own, their natural rate of spread seems to be relatively slow. However, we have witnessed these pests leapfrog over great distances to start new infestations resulting from the movement of infested firewood or other infested woody materials. There is no quarantine in place to stop the movement of this infested material. Our current best available tool is outreach and education to stop the movement of infested wood and woody materials.
Two invasive pests currently ravaging southern California should be of immediate concern to you:
The goldspotted oak borer (GSOB – Agrilus auroguttatus) attacks three species of oaks native to Southern California – coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and canyon live oak (Q. chrysolepis). Native only to southeastern Arizona in the US, the goldspotted oak borer (GSOB) was probably introduced before 2002 to Descanso in San Diego County on infested firewood brought from Arizona. It wasn’t until 2008 that GSOB was identified as the cause of death for thousands of oaks in San Diego; unknowingly, infested firewood from these dead trees was being moved around the county. By 2012, GSOB was attributed to having caused the death of more than 80,000 oak trees in San Diego County. That same year a new satellite infestation of GSOB was discovered in Riverside County some 50 miles distant. Long-distance satellite infestations were subsequently discovered in Orange County in 2014 and in Los Angeles County in 2015. Each of these new infestations are believed to have resulted from the import of GSOB-infested oak firewood originating from San Diego County. GSOB has the potential to be spread throughout California to areas with any of the three susceptible oak species. See www.gsob.org for more information.
The Invasive Shot-Hole Borers (ISHB – Euwallacea sp.) include two closely related beetles that are attacking and killing hundreds of thousands of trees in six southern California counties. These tree borers “farm” a treedamaging fungus (Fusarium sp. which is the beetle’s food source) inside the tunnels they bore in trees. This insect/pathogen complex is known as the Invasive Shot-Hole Borer/Fusarium Dieback complex (ISHB/FD). Both species of ISHB have a large list of reproductive hosts (trees in which ISHB can successfully multiply while they damage/kill the tree), and include native riparian species, oaks, landscaping trees, avocados, and at least one palm (see http://ucanr.edu/sites/pshb/overview/Hosts/ ). New reproductive hosts continue to be identified as the beetle spreads into new areas.
Both ISHB species are thought to have been introduced into California on wood packing material from Southeast Asia. Rapid spread throughout much of California is possible if aided by the movement of infested firewood, green waste, tree trimmings, or other woody materials.The first species of ISHB, Polyphagous shot hole borer and its associated Fusarium fungus, came to attention beginning in 2012 because of damage to backyard avocado trees in residential neighborhoods and a commercial avocado grove in Los Angeles County. The insect/pathogen complex is now known to be found over a wide area including most of Los Angeles County and parts of Orange, San Bernardino, and Riverside counties. In 2013 an outbreak in San Diego County was determined to be a second ISHB species, the Kuroshio shot hole borer and its associated Fusarium fungus. More information about the beetle/fungus relationship, how ISHB/FD weakens and kills trees, a map of current ISHB infestation, lists of susceptible tree/plant species, management options and other information about both species of ISHB can be viewed at www.PSHB.org.
For you to help us, we will be providing you outreach and education resources to share with your communities and keeping you informed with periodic updates on the status of these invasive pests.
The Emerging Tree Pests Education and Outreach Committee interagency group was initially formed in 2010 in response to GSOB, but was expanded to include ISHB/FD in 2016 after the scope, severity and potential spread of ISHB/FD was realized. This group has worked closely with some of the southern California Fire Safe Councils in wildland communities that have already been severely impacted by GSOB and ISHB. We would be glad to share our experience and education/outreach materials with any-and-all fire safe councils in the rest of California. Anabele Cornejo is the chair of the committee and can be contacted at firstname.lastname@example.org
The state-wide interagency California Firewood Task Force is a major partner in responding to GSOB and ISHB/FD. Moving infested firewood can spread these and other invasive pests with frightening speed. Information about the firewood threat can be found at www.firewood.ca.gov . Katie Harrell is the chair of the Firewood Task Force and can be contacted at email@example.com .
We look forward to a partnership with Fire Safe Councils like yours to reduce the possibility of these invasive pests becoming introduced and established in your community. Please don’t hesitate to contact us if you have any questions or suggestions on how we can help each other accomplish effective outreach.
Southern California Invasive Pest Coordinator
California Department of Forestry and Fire Protection