UC ANR experts, resources guide response to shothole borers in Bay Area

UC Cooperative Extension scientists, partners managed invasive beetle in Southern California

Late in 2023, a potentially devastating beetle was detected in the San Francisco Bay Area for the first time. But land managers, arborists and agency staff have one big advantage as they devise plans to control the invasive shothole borers (ISHB).

Thanks to collaborations led by University of California Agriculture and Natural Resources, they can draw upon the hard-earned experience of their colleagues in Southern California. Over the past decade, SoCal communities have lost “tens of thousands” of trees due to ISHB infestations, according to Beatriz Nobua-Behrmann, UC Cooperative Extension urban forestry and natural resources advisor for Los Angeles and Orange counties.

In one regional park, about 500 trees had to be removed in the span of just one year. “That kind of impact happened in many locations; a whole street might lose 90% of the trees – all of a sudden,” said Nobua-Behrmann, a member of a statewide network studying ISHB.

Spurred by such severe impacts, UC scientists have been studying ISHB and testing various control measures since about 2012. Their lessons are now informing efforts in San Jose – where the first case in the Bay Area was detected in November 2023 – and across the region.

“The UC ANR team is comprised of subject-matter experts,” said Drew Raymond, interim agricultural commissioner for Santa Clara County. “The team has compiled all of the experience from the agencies that have been doing work in Southern California and transplanted that experience here to Northern California.”

Lucy Diekmann, UC Cooperative Extension urban agriculture/food systems advisor, and Igor Lacan, UCCE environmental horticulture and urban forestry advisor, have coordinated regular meetings and trainings of Bay Area agricultural officials, land managers and arborists.

“Lucy and Igor have been instrumental in organizing our partners to establish an effective plan for shothole borers,” said Sara Davis, city forester for San Jose. “Because experts across the broader UC ANR network have many years of firsthand experience with this invasive pest, we are able to draw on their practical know-how to guide our monitoring, management and public education efforts.”

Davis is leading a trapping program in San Jose to determine how widespread ISHB is. Aside from a recent detection in the Santa Cruz Mountains, almost all of the approximately 30 confirmed cases in Northern California have been clustered along the riparian corridor of Coyote Creek through downtown San Jose. This pattern of intense but geographically limited damage was also seen across Southern California – notably in San Diego County along the Tijuana River Valley, where ISHB wiped out the willow population.

“I would expect us in the Bay Area to see this type of localized damage that is not fundamentally different from what they're seeing in Southern California,” Lacan said.

Unusually troublesome pest triggers deadly tree disease

The invasive shothole borers – a term for two species that are virtually indistinguishable, the polyphagous shothole borer and Kuroshio shothole borer – were first detected in Los Angeles in 2003. The tiny beetles, measuring 1.5 to 2 millimeters in length, became a major concern a decade later when swaths of urban forest began dying across LA County.

Infestations are harmful – and fatal for at least 17 tree species in California – because the fungus that the beetle “farms” as its food source causes a disease called Fusarium dieback. Alarmingly, ISHB make their home in a wide variety of trees; Nobua-Behrmann said 65 tree species in California have been identified as “reproductive hosts” where they can grow their populations.

“The fact that they are such a generalist species means that they can find a host almost anywhere,” she said, noting that sycamore, box elder, cottonwoods, oaks and willows are favorites of ISHB.

Furthermore, typical tools in the integrated pest management toolbox are unavailable or ineffective for this invasive beetle. Unlike most insects, these shothole borers mate with their siblings before leaving the tree, so they don't need to search for mates afterward. This means they are not attracted to the pheromone traps typically used for pest control; traps used for ISHB only work to track their numbers, not reduce them.

“Their biology limits what we can do,” Nobua-Behrmann said. “Since the beetles spend most of their lives inside the trees, it's also hard to reach them with insecticides.”

Largely hidden within trees, ISHB can build up their numbers, undetected for years. A tree with green and plentiful leaves may in fact be harboring a significant infestation. “It's easy for this beetle go under the radar and create a big population and a big problem before you even notice,” Nobua-Behrmann said.

Monitoring and early identification of infestations are crucial

Given this pest's elusive nature, monitoring and early intervention have proven to be essential in Southern California.

“All of the success stories have a major component of monitoring and detection; if you have a good monitoring program and you can quickly identify the trees that are infested, timely action can make a big difference,” said Nobua-Behrmann, citing Disneyland in Anaheim as one example where frequent surveys and robust monitoring prevented major impacts.

As most municipalities don't have the abundant resources of a world-famous theme park, Nobua-Behrmann pioneered a program in Southern California to train community members on recognizing telltale signs of the beetle. Specifically, they looked for its entry holes, which have a characteristically round shape and size, comparable to the tip of a ballpoint pen.

Beginning with UC Master Gardeners and UC California Naturalists and then members of the general public in LA and Orange counties (and later other SoCal counties), the program trained about 100 people on how to look out for the beetle. After verification by experts, volunteers were found to be nearly 90% accurate in identifying ISHB.

Although the volunteer monitoring program is on hiatus, Nobua-Behrmann said it had clear benefits that could potentially help other regions. “It would be great to get this program going in Northern California and hopefully get volunteers and people in the general public to help identify infestations there as well,” she said.

Statewide ISHB network spreads essential information

In addition to coordinating an in-person public training in San Jose in April, Lacan and Diekmann, the UC Cooperative Extension advisors, have been educating local UC Master Gardeners on how to spot signs of the invasive beetle.

For about a decade, Lacan has been warning people about the possibility of ISHB in Northern California, routinely including shothole borers in his presentations on “tree pests to watch.” “I've been doing this since before ‘day zero,' but there was not a whole lot of interest in ISHB, as you might imagine,” Lacan recalled. “But then all of that changed in fall of last year.”

In the past year, Lacan has done a dozen ISHB presentations, workshops and webinars, attended by a total of about 260 people – predominantly city foresters, land managers, production arborists and members of tree-related nonprofits.

Lacan noted that the most effective presentations have been at in-person events featuring UC ANR-affiliated experts such as Nobua-Behrmann, UCCE environmental horticulture advisor emeritus John Kabashima, and ISHB program staff Randall Oliver and Hannah Vasilis.

“Here is where we tap into our network,” Lacan said. “This is the power of the statewide shothole borers program.”

Another vital asset has been the collection of practical resources gathered by the ISHB program, the UC Integrated Pest Management team and partner organizations. One example is a deck of identification cards depicting how symptoms of infestation differ from species to species. Such detailed information can help managers determine whether a tree is truly infested – and thus allocate their limited resources more judiciously.

“These very specific, very seriously considered materials are the kind of thing that people really appreciate,” Lacan said. “It's not just a generic ‘it's kind of like this.'”

The symptoms, broken down by tree species, are also listed on the ISHB website. Raymond, the interim agricultural commissioner for Santa Clara County, said his team uses the website to get informed about ISHB and regularly refers community members to it.

“The ISHB website has been a great resource,” Raymond said. “It's full of important and user-friendly information.”

Communities learn to protect trees, adapt to shothole borers

If community members believe a tree is infested, they should review the symptoms of ISHB-Fusarium dieback. If the signs match what they are seeing, they should take a photo of the entry hole (with the tip of a ballpoint pen placed next to the hole as reference) and send images to their county agricultural commissioner's office or local UCCE advisor, who may then seek confirmation.

Extra eyes on urban forests are crucial to help experts identify potential “amplifier trees” – heavily infested trees, with more than 150 entry holes, that are often repeatedly reinfested by subsequent generations of beetles. They contribute to the recurring pattern of severe but localized infestations seen across Southern California – and now in San Jose.

New research suggests that removing severely infested trees – or just the most impacted limbs of those trees – can significantly lower the overall ISHB population and help less-infested trees in the area recover over time.

“You're not going to eradicate ISHB (at least not in Southern California); you're not going to get rid of them – you're going to have them forever,” Nobua-Behrmann said. “But you can keep them at a manageable amount.”

She also emphasized other actions the public can take to prevent the spread of ISHB, such as correctly disposing infested plant material – ideally chipping it to less than an inch in length (or as small as possible) and then composting the chips.

“It's also important to not move firewood and instead buy it where you will be burning,” Nobua-Behrmann said. “It's one of the best things people can do to protect trees from invasive pests.”

After identifying and removing amplifier trees, land managers and landscape arborists should have a plan for replanting, Lacan added. He said they should prioritize species that are less susceptible to the beetle, using his Pest Vulnerability Matrix tool that lists the major pests for different mixes of trees.

“We need to figure out how to have sustainable urban forests, even with this pest,” he said. “We know we can do it, largely thanks to our colleagues in Southern California. So the key lesson is to replant soon – choose smartly, but replant right away.”

Lawn-pocalypse! Surviving Drought

Ah, summer! The season of sunburns, pool parties, and… lawn droughts. If your once lush, green carpet now looks like a crunchy brown doormat, you're not alone. Let's dive into why your yard is staging a dramatic death scene and what you can do to...

Bermuda grass and weeds overtaking drought stressed turf grass.

A patch of former lawn, mostly dead, with a few green weeds and Bermudagrass

Shot Hole Borer Volunteer Training

Attend our training to become an invasive shothole borer monitor!

*Results from March 2023 ISHB Monitors Training*

Invasive shothole borers (ISHB) are wood boring beetles that attack many native and non-native trees in Southern California. These beetles bore tunnels into trunks and branches where they grow a fungus they use as food. The fungus causes a disease called Fusarium Dieback. Trees infected with Fusarium Dieback show branch dieback, canopy loss, and may eventually die. Infested trees become sources of beetles that can spread to surrounding hosts. This pest can also spread long distances through infested green waste and firewood, affecting new areas.

How you can help: Get trained, become an ISHB Monitor, and help us gather infestation data! In previous editions of the program, we learned that trained volunteers can identify ISHB-infested trees with 96% accuracy. This high accuracy of volunteer observations allows us to include the data collected through this program directly into the ISHB statewide distribution map. Knowing where beetles have spread will assist scientists, municipalities, and many other conservation agencies plan for management. Also, detecting infestations in their early stages allow for better chances of successful management. Your participation is needed to detect infestations throughout southern California.

Training for Monitors: You can become an ISHB monitor trained by scientists from UC Agriculture and Natural Resources. California Naturalists, Project Learning Tree Educators, and Master Gardeners are especially encouraged to attend, but curious minds of all ages are welcome.

Dates: Online training 7/7/2023. In person dates Ventura County 7/8/2023, Santa Barbara County 7/9/2023, San Diego County 7/14/2023, and Inland Empire (Riverside County or San Bernardino County) 7/15/2023 (specific locations to be determined).

Cost: Free.

Training Requirements:

• Registration is required.
• Attendance to online session is required.
• Attendance to one in-person session is required.
• Completion of the 1-hour free online eXtension Invasive Shothole Borer training is required.
• Monitors must create or already have a free account on iNaturalist.
• After the training, monitors must upload at least 5 observations to the UC ANR ISHB Monitoring Project on iNaturalist using the correct protocols ( UC ANR Invasive Shothole Borer Monitoring Project iNaturalist Guide ).

Note: Past participants of this program may choose not to attend the online session, but in-person session is required. Please make sure you contact us and let us know beforehand if you will not attend the online training.

AGENDA:

ishb sycamore

Climate-Change Resources

University of California UC ANR Green Blog (Climate Change and Other Topics) https://ucanr.edu/blogs/Green/index.cfm?tagname=climate%20change (full index)

Examples:

     -  Save Trees First: Tips to Keep Them Alive Under Drought https://ucanr.edu/b/~CdD 

     - Landscaping with Fire Exposure in Mind: https://ucanr.edu/b/~G4D

     - Cities in California Inland Areas Must Make Street Tree Changes to adapt to Future Climate  https://ucanr.edu/b/~oF7

Drought, Climate Change and California Water Management Ted Grantham, UC Cooperative Extension specialist (23 minutes) https://youtu.be/dlimj75Wn9Q

Climate Variability and Change: Trends and Impacts on CA Agriculture Tapan Pathak, UC Cooperative Extension specialist (24 minutes) https://youtu.be/bIHI0yqqQJc

California Institute for Water Resources (links to blogs, talks, podcasts, water experts, etc.) https://ciwr.ucanr.edu/California_Drought_Expertise/

UC ANR Wildfire Resources (publications, videos, etc.) https://ucanr.edu/News/For_the_media/Press_kits/Wildfire/ (main website)

      -UC ANR Fire Resources and Information https://ucanr.edu/sites/fire/ (main website)

            -Preparing Home Landscaping https://ucanr.edu/sites/fire/Prepare/Landscaping/

UC ANR Free Publications https://anrcatalog.ucanr.edu/ (main website)

- Benefits of Plants to Humans and Urban Ecosystems: https://anrcatalog.ucanr.edu/pdf/8726.pdf

 -Keeping Plants Alive Under Drought and Water Restrictions (English version) https://anrcatalog.ucanr.edu/pdf/8553.pdf

  (Spanish version) https://anrcatalog.ucanr.edu/pdf/8628.pdf

-  Use of Graywater in Urban Landscapes https://anrcatalog.ucanr.edu/pdf/8536.pdf

-  Sustainable Landscaping in California https://anrcatalog.ucanr.edu/pdf/8504.pdf

 

Other (Non-UC) Climate Change Resources

Urban Forests and Climate Change. Urban forests play an important role in climate change mitigation and adaptation. Active stewardship of a community's forestry assets can strengthen local resilience to climate change while creating more sustainable and desirable places to live. https://www.fs.usda.gov/ccrc/topics/urban-forests

Examining the Viability of Planting Trees to Mitigate Climate Change (plausible at the forest level) https://climate.nasa.gov/news/2927/examining-the-viability-of-planting-trees-to-help-mitigate-climate-change/

Reports and other information resources coordinated under the auspices of the United Nations and produced through the collaboration of thousands of international scientists to provide a clear and up to date view of the current state of scientific knowledge relevant to climate change. United Nations Climate Action

Scientific reports, programs, action movements and events related to climate change. National Center for Atmospheric Research (National Science Foundation)

Find useful reports, program information and other documents resulting from federally funded research and development into the behavior of the atmosphere and related physical, biological and social systems. Search and find climate data from prehistory through to an hour ago in the world's largest climate data archive. (Formerly the "Climatic Data Center") National Centers for Environmental Information (NOAA)

Think tank providing information, analysis, policy and solution development for addressing climate change and energy issues (formerly known as the: "Pew Center on Global Climate Change"). Center for Climate & Energy Solutions (C2ES)

Mapping Resilience: A Blueprint for Thriving in the Face of Climate Disaster. The Climate Adaptation Knowledge Exchange (CAKE) was launched in July 2010 and is managed by EcoAdapt, a non-profit with a singular mission: to create a robust future in the face of climate change by bringing together diverse players to reshape planning and management in response to rapid climate change. https://www.cakex.org/documents/mapping-resilience-blueprint-thriving-face-climate-disaster

Cal-Adapt provides a way to explore peer-reviewed data that portrays how climate change might affect California at the state and local level. We make this data available through downloads, visualizations, and the Cal-Adapt API for your research, outreach, and adaptation planning needs. Cal-Adapt is a collaboration between state agency funding programs, university and private sector researchers https://cal-adapt.org/

Find reports, maps, data and other resources produced through a confederation of the research arms of 13 Federal departments and agencies that carry out research and develop and maintain capabilities that support the Nation's response to global change. Global Change (U.S. Global Change Research Program)

The Pacific Institute is a global water think tank that combines science-based thought leadership with active outreach to influence local, national, and international efforts to develop sustainable water policies. https://pacinst.org/our-approach/

Making equity real in climate adaptation and community resilience policies and programs: a guidebook. https://greenlining.org/publications/2019/making-equity-real-in-climate-adaption-and-community-resilience-policies-and-programs-a-guidebook/ 

Quarterly CA Climate Updates and CA Drought Monitor Maps (updated each Thursday) https://www.drought.gov/documents/quarterly-climate-impacts-and-outlook-western-region-june-2022

 

 

 

 

Drought focus of Water Resources IMPACT magazine special issue

UC ANR experts address emotional toll of drought

Preparing the American West for prolonged drought is the focus of a double issue of Water Resources IMPACT magazine. The California Water Commission staff are guest editors for this special open-access edition of the magazine, which is published by the American Water Resources Association.   

Faith Kearns, academic coordinator of University of California Agriculture and Natural Resources' California Institute for Water Resources, is among the authors delving into how drought impacts people and the environment and how we can better prepare for the inevitable. 

The first issue, published on Feb. 14, focuses on water scarcity issues confronting California and the ways these issues affect different sectors. 

In “Trauma, Care, and Solidarity: Addressing the Emotional Toll of Chronic Drought,” Kearns highlights the effects of drought on mental health. She points to the spike in suicide hotline calls when wells ran dry in Southeast Asian communities in California's Central Valley.

By listening to Southeast Asian farmers, Ruth Dahlquist-Willard and Michael Yang of UC Cooperative Extension were able to “lighten the load” for them by providing pragmatic support, Kearns writes.

“The scale of some of these highly emotional issues – drought, wildfires, climate change – can make them seem incredibly difficult, if not impossible, to deal with,” Kearns said. “At the same time, they are affecting everyone living in the western U.S. on a daily basis. I wanted to highlight and provide models based on work that people – whether they are researchers, clinical psychologists, or Cooperative Extension advisors – are doing right now to ease the way.”

The authors who contributed to the double issue are a diverse array of Tribal experts, academics, nongovernmental organization thought-leaders, water managers and water policy influencers, each of whom brings their own perspective on the topic of drought. Their expertise and perspectives in climate science, water policy and water management will help inform drought-related decision-making and support policies that better prepare the state to thrive during periods of prolonged water scarcity.

In addition to Kearns, the first issue includes articles contributed by:

• Samantha Stevenson, University of California, Santa Barbara
• Jay Lund, University of California, Davis
• Ron Goode, North Fork Mono Tribe
• Andy Fecko, Placer County Water Agency
• Jeff Mount, Public Policy Institute of California, and Ted Grantham, University of California, Berkeley/UC Cooperative Extension
• Nat Seavy and Karyn Stockdale, National Audubon Society
• Kjia Rivers, Community Water Center
• Cannon Michael, Bowles Farming
• Michelle Reimers, Turlock Irrigation District

The January/February edition of Water Resources IMPACT magazine can be accessed, free of charge, on the American Water Resources Association website at https://www.awra.org under “Publications.”

The second issue, to be published in March, will focus on drought response, considering the options for adaptation. This two-part series complements the Commission's work on strategies to protect communities and fish and wildlife in the event of a long-term drought.

 

 

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