UC Irvine fights infestation of tree-killing bug

A deadly infestation of tiny tree-boring beetles from Southeast Asia has reached the UC Irvine campus, and school officials say several hundred trees will be removed in a matter of months while scientists grapple with the serious problem spreading throughout Southern California.

Infested trees have also been identified in surrounding property, including residential neighborhoods and public areas in University Hills.

“It’s a significant threat to all of our trees,” said Richard Demerjian, UCI’s director of environmental planning and sustainability. “We are in an ongoing inventory and really in the early assessment stage.”

Campus groundskeepers first noticed signs of a serious problem in December, and officials were able to confirm widespread infestation early this year. Tiny tell-tail boreholes in trees are often undetectable unless the bark is removed. It’s estimated the pest may have been introduced at UCI two to three years earlier.

The invader is known as the Polyphagous Shot Hole Borer, a tiny beetle about the size of a sesame seed. It was first identified in Southern California in 2003, with major infestations beginning to surface in 2011, first in Long Beach and then Los Angeles. It has now spread to Riverside and Orange counties and, more recently, San Diego.

The beetle infects a wide variety of tree species by boring to the core to begin its reproductive cycle. A fungus secreted by the beetle chokes the pulp and kills or seriously damages the host tree. Scientists have traced the beetle’s origin to Southeast Asia.

UCI has assembled a faculty team to work on a management strategy with experts from the UC Division of Agriculture and Natural Resources as well as UC Riverside plant pathologist Akif Eskalen, who first identified the beetle fungus as the source of disease in the trees. There is no known treatment for infected trees.

According to a news release on the UCI website, of the more than 25,000 trees on campus, about 1,000 have been identified as infested, most of which will need to be removed. At least 16 species of trees have been infected, with varieties of sycamores a favorite host of the beetle.

In an April 15 email to students and faculty, Vice Chancellor Wendell Brace explained of the problem and the developing emergency plan.

“We regret that many large trees will have to be removed as part of this management process, but this is a necessary step in protecting the remaining healthy trees in our urban forest,” he said in the message. “Experimental treatment and prevention programs will place a priority on saving large mature trees, such as the 40- to 50-year-old native sycamore trees in the central campus.”

The university will develop a program for planting replacement trees as information becomes available on species resistant to the Polyphagous Shot Hole Borer infestation, school officials said. Proper disposal of the infected wood is also under examination.

Officials from the Irvine Campus Housing Authority will be made available to work with off-campus neighbors who have concerns.

As the UCI spokesman on the matter, Demerjian expressed some of the sentiments among the scientists and students who lament the only course of action right now is tree removal. “It’s hard to watch so many trees get cut down, but people understand the necessity of this in order to manage the problem.”