Sycamore trees at Sayre Village Apartments in Sylmar could not survive despite the treatment against the dreaded Polyphagous Shot Hole Borer (PSHB) pest.

In June, an owner of the Sayre Village Apartments in Sylmar noticed that one of its large Sycamore trees was in decline, and asked the landscapers for the complex to examine it.

The landscaping company for the apartments, Stay Green, examined the trees and then contacted Arborjet, the company that fights a voracious tree-killing beetle known as the Polyphagous Shot Hole Borer (PSHB). Arborjet is a source provider for Stay Green.

The trees were scheduled to receive life-saving trunk injection treatments on July 6. But when the trees were inspected again, it was determined that too much pest damage had already occurred. One tree was already dead and the other was too infested with the beetles to be saved by the injections. 

Instead representatives gave demonstrations of how the treatments would be administered.  

Dawn Fluharty, an Arborjet regional technical manager and California pest control advisor based in San Francisco who attended the planned demonstration, described the PSHB as “an exotic ambrosia beetle” not native to the state. It came here from Southeast Asia, and was first detected in 2003 in Southern California. It is currently found in L.A., Orange, San Bernardino, Western Riverside, and San Diego Counties.

The actual beetle is no bigger than a half-grain of rice, Fluharty said, but breeds constantly and multiplies rapidly.

“The beetles colonize and live in the tree, where they breed,” Fluharty said. “As long as the tree has water and moisture flow, the beetles keep multiplying. When the tree dies, all the beetles leave.”

The beetle attacks a large number of plant species, the majority of which are hardwoods, Fluharty said. The “ambrosia” name refers to a symbiotic fungus that is carried by the female in special organs in her mouth parts. Infection with the fungus can cause leaf discoloration and wilting, dieback of entire branches, and will eventually kill the tree.

This invasive pest can endanger more than 300 species of trees including California native oaks, sycamores, palm trees and even avocado trees.

An infestation of beetles can kill healthy sycamores like the ones at the Sylmar apartments in as little as six months, Fluharty said.

Because it is not a native pest, it has no natural predators here and the endangered trees have no natural defenses, Fluharty said. Companies like Arborjet are fighting and killing them through the chemical injections into trees, which can be effective up to two years.

Many homeowners don’t know about the destructive PSHB and have been left on their own to figure it out if something is wrong, Fluharty said.

“Depending on the tree, the beetles can reproduce every six weeks, and a lone female can reproduce 20-40 new beetles,” she said. “About 80 percent of new beetles are female, and the brothers and sisters will mate. When new beetles are born they start reproducing before they will exit a tree. If the tree is healthy, the preying females will bore right back into the trees.”

She suggested that homeowners and property owners should constantly examine trees for wet spots on tree trunks as an indicator of a possible infestation. The wet spots can be caused by the fungus created by the females. 

Calls were placed to the Encino offices of Taylor Burke and Associates, which manages the Sylmar apartment, and to Stay Green in Santa Clarita but no one at either location was available to comment on what the next step would be for the infested trees.

Leave a comment

Your email address will not be published. Required fields are marked *