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GSOB Management by La Jolla Band of Luiseño Indians

The goldspotted oak borer beetle (GSOB) has been causing significant tree mortality in the native California oak woodlands. These beetles are invasive to this area, and host oak species have not evolved natural ecological defenses to protect against this new harmful pest. Cultural and economic resources on the lands managed by the  La Jolla Band of Luiseno Indians have been severely impacted by GSOB. Hundreds of trees on the lands managed by the Band are dead or in the process of dying due to this beetle.

A Natural Resource Program has been developed within the Tribal government to mitigate the significant number of hazardous trees, creating falling hazards and high wildfire fuel loads. The Band has been utilizing forestry funding from the California Department of Conservation and the Bureau of Indian Affairs to implement sound forest management practices and develop the capacity to manage the GSOB threat and reduce wildfire fuel loads. With a rapidly changing climate, disturbances to the forest are on the rise. La Jolla works to combat climate change and mitigate these disturbances through active forest management practices.

The natural resource program employs a crew of 7 workers, two of which are seasoned tree cutters, two biomass processors, two managers, and an Intern. Currently, all the forestry work is grant funded, but the Band is researching the viability of revenue from fuel reduction work to provide long-term funding for the program.

Biomass Utilization is vital because wood is a finite resource, and the oak woodlands currently have a negative growth rate. Utilizing the biomass provides an opportunity to promote active forest management and conserve a valuable Tribal resource. It is essential to use salvaged wood to benefit the Band and the oak woodlands. This helps to reduce the importation of firewood from outside areas and to reduce our carbon footprint by producing a value-added product which in turn helps reduce the net carbon production, reducing climate change stressors. Having firewood is an excellent use of the oak resource because it can be quickly processed, and GSOB does not remain in firewood seasoned for two years.
A critical factor in this process is that the firewood stays in an area near where it was taken from to help prevent the spread of forest insects such as Gypsy Moth, the Spotted Lantern Fly, or the Emerald Ash Borer. The Tribe is seeking additional funding to purchase wood processing equipment and a firewood kiln to heat treat firewood and create a local source of insect-free kiln dried firewood. The Tribe is also researching the viability of producing additional wood products such as clocks, slabs, lamps, and souvenirs.

Tree Removal is necessary for La Jolla’s Forest management to cut down and remove dead trees. This is necessary for several reasons, including pest control, public safety, and forest health. A dead tree poses a risk of falling, damaging infrastructure, or property, damaging other trees, or causing injury to humans. Downed trees can also block roads delaying emergency response and traffic. For these reasons, it is critical that dead and dying trees be removed to maintain the forest's health and safety.  The Band is also partnering with local tribes and agencies to develop capacity and provide training for tree felling. The Band has removed over 300 trees in the past few years.

Tree Health Surveys are conducted annually to identify trees infested with GSOB. The first step in this survey is to rate the crowns of the trees. The crowns are rated on a scale of 1-5, 1 being a fully healthy crown and five completely dead crowns. The next step is to rate the bark stain. Bark stain is rated on a scale of 1-4, 1 being 1 to 5 stained areas on the lower stem and 4 being evidence of bark cracking on the main stem. The next step of the survey will be rating exit holes from GSOB. This is done on a scale from 1-3, 1 being at least one exit hole found and 3 being exit holes found throughout the tree’s main stem. This survey will help determine which trees are still healthy, can be treated with pesticides, and which trees are dying and should be salvaged or sanitized.

Integrated Pest Management based pesticide application is one of the ways that La Jolla decreases GSOB damage in oak trees. The pesticide program utilizes GSOB life cycle information to apply timely and targeted pesticide applications directly on the bark surface to reduce unnecessary pesticide applications. Current funding and environmental concerns have limited pesticide application to high-value trees. High-value trees are culturally important trees or trees that provide crucial shade and aesthetic value to campsites.

Silviculture, a registered professional forester prescribes silvicultural practices, including pruning, replanting, prescribed fire, thinning, salvage, and sanitation. Trees must be removed to increase forest health and could be marked for removal because they are hazardous, dead, infested, or to reduce overcrowding. Salvage is the process where dead trees are identified and harvested. Sanitation is the process where infested trees are also identified and harvested in a way that reduces insect population and limits the spread to surrounding healthy oak trees. Thinning is the final step in the forestry prescription. Thinning is the process where trees that are causing overcrowding are removed. In a plot of overcrowded trees, the largest and healthiest trees in a radius of about 15 feet are selected to stay. All other trees in that radius are removed to allow the most significant trees to grow with less competition. Historically this method has been used to treat beetle infestations and can be applied to La Jolla Reservation as another tactic to manage GSOB infestation today.

Outreach on the Jolla Indian Reservation helps spread awareness on how to limit the spread of GSOB. Outreach programs include “buy it where you burn it” signage and outreach cards sold with every firewood bundle. The cards explain that taking wood home from the campground is not safe and may lead to insect infestation.

Internships are funded by the California Department of Conservation and the Bureau of Indian Affairs. The current intern is a forestry undergraduate at Oregon State University and is leading the nursery construction project. The internship allows the student to gain experience while helping the Band to complete planned projects that have been understaffed. The Intern is also working on tree propagation and assisting with tree health surveys and reports.

Research Partnerships with several universities are currently working to solve natural resource problems. San Diego State University has partnered with the Climate Science Alliance and local tribes to investigate oak tree climate change adaptation response. The Bureau of Indian Affairs has also funded the tribe to partner with the University of California Riverside (CAL Fire funds UCR) to investigate heat treatment practices and the potential for Indigenous-based prescribed fire to be used as a landscape-level management tool for the control of GSOB.  The Tribe is also seeking additional funds to partner with UCR to investigate a wasp identified as Balcha indica and its potential as a biological control for GSOB.

(Write-up courtesy of Joelene Tamm, Natural Resource Manager with La Jolla Band of Luiseño Indians)