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:

When tiny tree-killing beetles first arrived in Southern California several years ago and began destroying urban and riparian forests, they raised widespread concerns among both tree experts and affected communities. More recently, invasive shothole borers have captured far less attention, and many people may think the pest threat is over. Unfortunately, it's not!

While significant progress has been achieved in invasive shothole borer research, surveying, trapping, and management programs, these beetles are still an ongoing threat to the state's urban and wildland trees. Continue reading to find out what you can do to be part of the solution to this invasive pest issue.

What are invasive shothole borers?

Invasive shothole borers (ISHB) (Figure 1) are sesame seed-sized beetles. They tunnel into trees and introduce a fungus that they use as their food source. As the fungus grows, it causes a plant disease called Fusarium dieback that leads to branch dieback, tree decline, and, in many cases, tree death.

The beetles and fungi can live and reproduce in a wide range of tree species including more than 65 types of trees found in California. The most highly susceptible trees include many species that are commonly used for landscaping like sycamores, some oaks, cottonwoods, and box elder. Invasive shothole borers can attack healthy, stressed, or diseased trees.

What's the problem?

Urban trees provide us with many benefits to our health and our economy. The trees around us reduce our stress levels, provide shade, allow for energy conservation, improve air quality, reduce stormwater runoff, and provide habitat for wildlife. It is important to protect them from invasive pests, like invasive shothole borers, which could potentially kill one out of three urban trees in California.

ISHB-infested trees can quickly become a public safety hazard. Trees with heavily infested branches can be especially hazardous. The combined damage of the fungal disease and the beetle's tunneling activity weakens the wood, causing limbs to break and fall (Figure 2). In addition, severely infested trees will become a constant source of beetles that can disperse and infest neighboring trees.

Where are they found?

These non-native beetles are now established in many areas of Southern California and the Central Coast. Female beetles are capable of flight over short distances, allowing the pest and its associated fungi to spread into new areas. Beetles can also be transported in infested firewood and green waste, leading to dispersal over much greater distances.

What to look for

Because they are very small and spend most of their lives inside their tree hosts, you probably won't see the beetles themselves, but there are several common signs and symptoms associated with their infestations: ?Beetle entry holes: When the beetles tunnel into the trees, they make small, perfectly round holes, each about the size of the tip of a medium ballpoint pen (Figure 3).

• Tree response symptoms: One or more of the following symptoms usually accompany the presence of entry holes (symptoms vary by the tree species): dark, wet staining; thick gumming; sugar-like buildup; or boring dust (resembles fine sawdust).
• Dieback: Dead or wilting branches can be a sign of a severe infestation. If you see dieback on trees, check for entry holes on the trunk or the branch collars.

What you can do

Several steps can be taken to prevent pest problems and manage infestations.

• Keep your trees healthy. Proper irrigation and maintenance will keep trees strong and help protect them from ISHB and other pests.
• Check your trees. Look for the common signs and symptoms listed previously. Regular monitoring ensures that infestations are managed early, before they cause dieback or tree death.
• Confirm suspected infestations using the detection tool on www.ishb.org. ?Know your management options. When possible, pruning infested branches is recommended. Low and moderately infested trees can be treated. You will need to contact a licensed professional to apply the treatments. Severely infested trees may require removal.
• Take care of green waste. The beetles can survive in cut wood for weeks or even months. Proper disposal of green waste includes chipping infested wood, followed by solarizing or composting the chips.
• Consult a professional. A certified arborist or pest control professional would be able to provide recommendations based on the conditions of your tree. Your County Agricultural Commissioner's office and UC Cooperative Extension office may have more knowledge about current ISHB monitoring and management programs in your area.
• Use locally sourced or heat-treated firewood. These beetles and other tree-killing insects often reach new locations by hitchhiking in firewood. Buy firewood where you will use it, and only buy the amount of firewood you need.

Visit www.ishb.org for more information about invasive shothole borers.

[Originally featured in the Summer 2022 issue of UC IPM's Home & Garden Pests Newsletter.]

Results help inform best practices for managing the disease-causing beetle

The University of California, Irvine campus is home to a vast urban forest consisting of approximately 30,000 trees located in a mix of landscape, riparian and open space settings. In the mid-2010s, that forest came under threat from an invasive species of beetle that arborists and pest researchers were just learning about – the polyphagous shothole borer.

The tiny beetles, which may have arrived in California from their native Southeast Asia via infested shipping materials, tunnel into trees and introduce a fungus that serves as food for adult beetles and their larva.

As the fungus grows, it colonizes the tree's vascular system, blocking transport of water and nutrients. This causes a disease called Fusarium dieback that can kill branches or entire trees.

Shothole borers attack more than 100 species of trees and can live and reproduce in more than 65 tree species found in California. However, they seem to prefer box elders, sycamores and willows.

One reason the beetles were such a threat at UCI was the high number of sycamores on campus, especially in Aldrich Park at the campus center. Hundreds of cottonwoods, native willows, golden rain and coral trees also were affected. In total, the beetles attacked more than 2,000 trees, including 75 different tree species.

A variety of approaches to controlling beetle

To better understand and tackle this problem, UCI's Facilities Management department and Office of Environmental Planning and Sustainability collaborated with researchers affiliated with UC Agriculture and Natural Resources and UC Cooperative Extension. In addition, pesticide-manufacturing companies, pest control advisers and arborists provided materials and labor to help offset the cost of research.

“UCI was the perfect testing ground to determine integrated pest management strategies for this beetle/disease complex,” said John Kabashima, UCCE environmental horticulture advisor emeritus. “Our research was multifaceted, delving into early detection, monitoring and sampling, and cultural and chemical management.”

Kabashima said UCI provided the researchers with “a lot of freedom” to try a variety of approaches and study the results over time.

“We could cut down and sample trees or leave selected infested trees alone; we explored a variety of pesticide/fungicide combinations and application techniques,” he said. “That freedom resulted in many of the management solutions that are used today to effectively control this pest.”

UCI and the researchers also established a full inventory of affected trees on campus, evaluating severity of infestation by the number of entry/exit holes and signs of dieback. One important key to management is getting rid of “amplifiers” – heavily infested trees that are both hazardous and a source of beetles to spread to other trees.

“Typically, shothole borer infestations begin with just a few trees that for some reason are highly attractive to the beetles – perhaps based on tree species, tree spacing, irrigation conditions or other factors,” Kabashima said. “Over time, the beetles and fungus multiply largely undetected in those few trees. When the beetle population reaches a critical point and the trees begin to die, the female beetles fly to adjacent trees in a secondary invasion, eventually infesting many trees over a large area.”

An opportunity to diversify UCI's urban forest

At UCI, that initial invasion took place in landscaped areas containing many large, majestic sycamores that were planted when the campus began operations in the mid-1960s.

Over several years, UCI removed 700 heavily infested trees, including many of those historic sycamores, and replaced them with other tree species.

“We tip-toed into tree diversity, looking for other tree species that might be less susceptible to attack; we looked at 300 tree species that could be suitable for creating a more diverse tree forest as opposed to a street tree approach.” said Matthew Deines, senior planner with UCI Campus Physical & Environmental Planning. “We also planned for some redundancy in how we planted: If we had space, we would plant two trees of a single species and then plant backups with other species – what we did not want was a monoculture.”

Today, the forest at UCI is very different than it was in 2015. While shothole borers have not been eliminated completely, their presence is reduced significantly, and UCI now has the tools to manage them effectively. Reforestation efforts resulted in a diverse treescape that is not only more sustainable but also beautiful.

“Managing a 1,500-acre campus with 30,000 trees is a never-ending process,” said Richard Demerjian, UCI's assistant vice chancellor, Campus Physical & Environmental Planning. “Our forest continues to evolve, with an ongoing focus on increasing diversity and plant health.”

Demerjian also noted that UCI is now starting to consider planting new sycamore trees on a limited basis.

A primer on effective shothole borer management

Whether managing a forest of thousands of trees or just a few trees, landscape managers and residents can apply many of the lessons learned at UCI to control invasive shothole borers and other tree pests.

• Avoid monocultures. Tree diversity provides beauty and resiliency.
• Keep trees healthy. Proper irrigation and maintenance will keep trees strong and help protect them from shothole borers and other pests.
• Check trees. Look for the common signs and symptoms of infestation such as beetle entry/exit holes. Regular monitoring ensures that infestations are managed early, before they cause dieback or tree death.
• Confirm suspected infestations. Use the detection tool at www.ishb.org.
• Review management options. For trees with low infestation, prune the infested branches and monitor the tree's health over time. In non-riparian, urban settings, consider treating low and moderately infested trees with pesticides/fungicides demonstrated to be effective against the pest-disease complex (A licensed professional will be needed to apply the treatments). Severely infested trees may require removal.
• Call in a professional. A certified arborist or pest control professional would be able to provide recommendations based on the tree's condition. The local county Agricultural Commissioner's Office and UC Cooperative Extension office may have additional knowledge about current shothole borer monitoring and management programs in your area.
• Take care of green waste. The beetles can survive in cut wood for weeks or even months. Proper disposal of green waste includes chipping infested wood, followed by solarizing or composting the chips.
• Replant wisely. Begin planting new trees only after removing all amplifiers and establishing an ongoing monitoring program. Consider the current concentration of tree species when deciding what type of trees to plant.

UCCE's Dr. Beatriz Nobua-Behrmann will present "Using an Integrated Pest Management Approach to Shothole Borers" at the Long Beach Landscape Expo at noon on Oct. 14.

This workshop will be focused on the invasive shothole borers (ISHB; tiny invasive beetles that attack trees) and Fusarium Dieback (FD; the fungal disease vectored by the beetles). This insect-disease complex is responsible for the decline and death of hundreds of thousands of trees in Southern California.

The workshop will include information on the basic biology of the beetles and fungus and how to identify infested trees. I will also share the latest research findings on ISHB-FD management and distribution in Southern California. I'll review the best management practices and what to consider when making decisions regarding management of individual trees.

Learning Objectives:
1. Understand the basic biology of ISHB-FD and how it affects trees
2. Learn about management options for ISHB-FD and when to use each of them
3. Learn how to prevent the spread of this dangerous pest

Seminar Date: October 14, 2021 12:00 PM

Seminar Cost: $30 - Save 20% on this seminar using coupon code: 20TLE2021Lx

Click here for Seminar Details

Click Here to Register

Beatriz Nobua-Behrmann, Ph.D.

Urban Forestry and Natural Resources Advisor, University of California Cooperative Extension

Dr. Beatriz Nobua-Behrmann's research background is in insect-plant interactions. She got her PhD in insect ecology from the University of Buenos Aires, in Argentina.

Dr. Nobua-Behrmann joined the University of California Cooperative Extension in 2017 as a Research Associate and managed the invasive insect pests project until she became an advisor.

Currently, Dr. Nobua-Behrmann is the Urban Forestry and Natural Resources Advisor for the University of California Cooperative Extension, serving the counties of Los Angeles and Orange. Her program is focused on the management of urban forest pests, like the Invasive Shot-Hole Borer beetles and the Gold-Spotted Oak Borer.