Fall 2025 Newsletter
By Nikki Evans and Brooke Ryan
Image 1: Brooke Ryan holding cat-faced orb weaver (Araneus gemmoides)
The relationship between trees and wood-boring beetles is stunning in its chemical complexity. Wood-boring beetles tunnel into trees, using them for food, shelter, or as a space for farming fungus to feed their young. These beetles tend to prefer stressed trees because they are less able to fight back. Healthy trees have natural defenses to recover from and prevent injury including the production of lethal compounds in response to a beetle infestation and the ability send out chemicals that prompt other trees to increase their own chemical defenses. Healthy trees also respond to wounds by producing callus tissue and sap to contain damage, which can kill or trapping wood-boring beetles and their larvae.
But stress weakens a trees ability to enact their natural defenses, and so many species of wood-boring beetles prefer stressed trees. Beetles have even evolved ways to detect which trees are stressed: ethanol. Trees release ethanol as an emergency energy source when stressors such as fire, drought, or disease impair a trees ability to produce energy from aerobic respiration. Wood-boring beetles can detect ethanol and so the tree’s desperate bid for survival also becomes a beacon for beetles to attack.
What happens when you introduce prescribed fire to the equation? Prescribed fire is an important land-management tool, intended to protect human and natural communities by preventing fuel buildup that could lead to scorching-hot wildfires, but it is also a stressor. Can prescribed burns inadvertently boost beetle populations, potentially increasing tree mortality? This is the question that Brooke Ryan is studying at Sedgwick Reserve, relying on the Reserve’s mosaic of prescribed burns conducted over the last four years.
Having graduated from UCSB with a double major in Environmental Studies and Spanish in the spring of 2025, Brooke works as a lab technician with plans to get a PhD in Entomology or Invertebrate Ecology. As an advocate for the ecological role of fire in native landscapes, she hopes her research will help improve forest management techniques related to controlled burning in oak woodlands and aid in understanding how these beetles should be managed in fire-prone ecosystems. Brooke was willing to take a break from her busy schedule to answer some of our questions about beetles, fire, and field work. Read on to learn more!
Image 2: Unidentified bark/ambrosia beetle collected from an ethanol-baited pheromone trap at Sedgwick Reserve on July 25, 2025
Tell us a little about your research at Sedgwick.
I am investigating the relationship between native wood-boring beetles and fire
events in oak woodlands. I hypothesized that prescribed burning would increase beetle activity in oaks due to increased stress, ultimately leading to worsened tree health conditions. To learn more, I surveyed visual symptoms of beetle activity such as bore holes, bore dust, and galleries. I
also looked at overall tree condition, implemented pheromone traps baited with
ethanol to get beetle counts, and did a xylem staining method to understand how
the trees are impacted on a physiological level. Preliminary results suggest prescribed burning may increase the likelihood of beetle infestation, or that fire and beetle impacts are combining to reduce tree health.
Fire has been a vital part of California’s ecosystems for thousands of years and was long used by Indigenous peoples for cultural and land management purposes. After centuries of Indigenous oppression and fire suppression, Western society is beginning to make reparations, with practices such as prescribed fire and cultural burning returning across California. I hope research such as this can help improve forest management techniques related to controlled burning in oak woodlands.
Tell us a little about the lab you work within, and how your research connects.
I work with the Anderegg Landscape Ecophysiology and Function (LEAF) Lab and Carla D’Antonio’s Vegetation Ecology Group (VEG) Lab, both at UC Santa Barbara. The LEAF lab strives to understand how environmental factors affect plants and landscapes from a physiological perspective, using methods such as remote sensing, hydraulic conductivity testing, and pressure chambers to find plant water potential. Carla D’Antionios lab focuses on understanding various triggers of vegetation change such as fire, invasion, drought, and environmental processes to inform restoration methods.
Can you tell us a little about bark beetles in our local oaks in general. Are they a major threat to our trees? Are there things the general public can or should do to protect their oaks from bark beetles?
Wood-boring beetles target stressed and dying trees, creating tunnels known as galleries. Some beetles species use these galleries to lay their larvae and introduce fungi that serve as their food. Other species use the galleries as shelter while feeding on the tree’s cambium, a vital living layer responsible for transporting nutrients.
Native bark beetles and wood boring insects are a natural part of most forest ecosystems and generally do not cause significant harm. However, factors such as global warming, drought, and invasive species can significantly alter native ecosystems, so it is important to be aware and pay attention to your oaks. Look into the symptoms of Sudden Oak Death (SOD) and invasive pests in your area, such as the Goldspotted Oak Borer (GSOB). If you notice an unusual amount of beetle activity, fungus, or rotting on your oaks, you should report it to your county Agricultural Commissioner’s Office!
Image 3: Evidence of wood boring beetles.
What is your relationship with fieldwork like: e.g. What do you like about it? What do you find challenging?
Field work is one of my favorite parts of doing research. Even though it can be physically and mentally demanding at times–especially when you have to wake up before dawn to go out and collect samples–it is extremely rewarding. For me, being outside is the best reminder of why it is so important to continue learning about our natural environment.
Do you have any advice for people hoping to launch a career in the field sciences?
Don’t get discouraged if something goes wrong in the field! While we can do research to better understand the natural world, we will never be able to control it. You can’t expect to anticipate what might happen when you are doing fieldwork, but it is all about adapting and finding a solution. By the end you’ll walk away with new discoveries about the natural world, along with some awesome tales of your adventures!
Thank you, Brooke for sharing your research with us!
Image 4: Pheromone trap for catching beetles