The university is combating a tiny invasive beetle that has emerged as a virulent pest in Los Angeles, Orange and Riverside counties.
The polyphagous shot hole borer beetle, which is native to Southeast Asia, is only about the size of a sesame seed, but can damage and kill trees. Female beetles bore through the tree’s bark and create voids, depositing fungus that spreads throughout a susceptible tree. The female then lays eggs in these cavities and when the eggs hatch, the larvae eat the fungus. When mature beetles leave the burrow, they carry the fungus to another tree.
The university began an active inspection program after the beetle was discovered on campus in 2015. Vendors and county and state agencies have visited campus to inspect, observe, advice, treat and collaborate on treatment protocols.
About half of the 6,000 trees on university land are maintained, and one in five of them shows signs of infestation. However, in the past 15 months, more than 67 percent of the 600 affected trees have been treated and saved, says Richard Farmer, manager of horticulture and landscape services.
“Unfortunately, some trees are not responding and must be removed to ensure the safety of our students, staff and visitors,” Farmer says. “When a tree is determined to be too severely damaged, we will always put the safety of the campus community first.”
All species of trees on campus, except for ficus and pine, are at risk of infestation.
Symptoms of a beetle attack differ among trees, but one of the telltale signs is a tiny round entry hole bored by female beetles. The fungus deposited by the beetles can cause dark stains around the black entry holes, discolored wood, leaf discoloration and wilting, and dieback of branches.