A California oak moth caterpillar outbreak is currently sweeping the campus, leaving trees defoliated and the campus community concerned.
The caterpillars, Phryganidia californica, are native to the Bay Area and outbreaks such as the current one that campus students and staff are facing happen sporadically along the California coast, according to Peter T. Oboyski, executive director of the Essig Museum of Entomology.
“No one knows why they explode in specific locations,” Oboyski said in an email. “They do not seem to attack the same place twice.”
Last year, Oakland experienced a similar outbreak of oak moths and caterpillars, however, they did not do any lasting damage to the California live oaks, according to the San Francisco Chronicle.
If weather conditions stay favorable, the campus may experience a second round of both moths and caterpillars, although the current invasion should start disappearing over the next few weeks, said Oboyski in an email.
“I was a GBO leader and these caterpillars just came out of the trees,” said Kayleigh Nealon, a campus junior and member of the campus’s entomology club.
She said she recognizes them as caterpillars — not worms — and upon hearing how they most likely will not return to campus for a while, described them as a bit of a “blessing.”
Some of the concerns about the large number of caterpillars center around the defoliation of trees on campus. Defoliation has been extreme this year due to the higher number of caterpillars, Oboyski said in the email. Once the leaves are gone, the caterpillars will hang from silk draglines looking for more food or places to pupate. They will then go through the metamorphosis required to become mature moths.
“Caterpillars are one of my biggest fears and the past two weeks of the semester, being on campus with them has not been a fun experience,” said campus junior Mollie Tessler in an email.
According to the University of California Agriculture and Natural Resources website, if the caterpillars are disturbed, they tend to “wiggle vigorously” and often release from their threads, dropping onto unsuspecting victims below.
Gillian Edgelow, a staff member in the department of gender and women’s studies, has noticed the numerous caterpillars outside of Barrows Hall, where she works.
“The trees nearest where I work are totally denuded of leaves, and the handing larva are everywhere,” Edgelow said in an email. “It’s quite an obstacle course to get into and out of the building without acquiring one on your shoulder. Eww!”
Although the trees may be less aesthetically pleasing without their foliage, Oboyski said the campus trees will recover with fresh leaves during the springtime. He also cautioned against spraying pesticides, which would kill other native species, including the natural predators of the caterpillars.
“While the naked trees do appear unsightly, and the bungee jumping caterpillars are a nuisance, it is all cosmetic and a small price to pay to work and study on a campus that hosts native ecosystems including streams, redwoods, peregrine falcons, monarchs, and yes, oak moths,” Oboyski said in the email.