Longhorn Borer Beetle Found in the Bay Area

The dreaded longhorn borer beetle that has ravaged eucalyptus trees throughout Southern California has been found in the Bay Area, the first discovery north of Santa Barbara.

Originally from Australia, the inch-long pest has no natural enemies here and has killed thousands of eucalyptus trees since it was first detected in this country five years ago.

Forestry officials had hoped to contain its spread by cutting down infested trees and regulating the transportation of eucalyptus firewood. But since last month, officials have captured some of the insect’s larva in three trees in Alameda County.

Entomologists are uncertain how well the black-colored insect, which has long antennas and zigzag markings on its tough outer shell, will adapt to the cooler Bay Area climate. Some experts say it could kill thousands of trees in what was once the world’s last concentration of eucalyptus groves free of borer infestation.

“It has a potential of killing a third of all trees” in the Bay Area, said Jim Laughlin, a state forester in San Bernardino County, where the beetle killed hundred of trees.

Wait-and-See Attitude

Bay Area officials say they are taking a wait-and-see attitude about the significance of the new pest.

“The environment up here is more favorable to the eucalyptus than in Southern California. So the extent of damage shouldn’t be as severe. The truth remains to be seen,” said John Nicoles, a land management specialist for the East Bay Regional Park District, where eucalyptus groves cover more than 1,500 acres of parkland.

The true impact of the pest will be felt by homeowners who will have to pay up to $10,000 for removing eucalyptus trees killed by the beetle from their yards, Nicoles said.

Forestry officials fear trees killed by the beetle will become fire and safety hazards.

“Very, very hot fires develop from eucalyptus” and are harder to extinguish, said David Neff, a state forestry official.

Imported From Australia

Eucalyptus trees were imported from Australia at the turn of the century. The trees grew well in California’s semi-arid climate. The trees are not grown commercially.

The borer typically attacks trees that are older, unhealthy or under environmental stress, such as drought and frost damage, said Tim Paine, an entomology professor at UC Riverside. Healthy trees can thwart the beetle by drowning its larva with sap.

The beetle attacks the trees by laying its eggs beneath their bark. The hatched larva bore deeply into the tree, drilling deep holes that eventually kill the tree.

Paine said the beetle was probably shipped from Chile to California in wooden crates infested with beetle larva. Though the borer beetle can fly, he said it most likely made its way to the Bay Area by hitching a ride in a stack of firewood.

Pesticides are ineffective against the pest, because the larva are so deeply embedded in the tree, Paine said.

Researchers at UC Riverside are experimenting with introducing some of the beetle’s predators from Australia to keep the beetle population in check. Researchers have unleashed the Australian beetle-killing wasp, which preys specifically on the longhorn borer’s larva. But so far, the wasp has adapted poorly to its new environment. “It’s simply one of those things you have got to shrug your shoulders about. We’re going to have to live with it,” Nicoles said.