Eucalyptus Killer Found in Valley : Beetle Infestation, Often Carried in Firewood, Is Deadly to Weakened Trees

A deadly beetle infestation that could threaten millions of eucalyptus trees in Southern California has spread to the San Fernando Valley, authorities said Thursday.

Evidence of the long horned beetle, a wood borer, has been found in three dead trees in Sylmar, prompting warnings from Los Angeles County forestry officials against transporting eucalyptus firewood in the Valley.

“It’s a time bomb,” said Herbert Spitzer, senior deputy forester for Los Angeles County, who made the Sylmar discovery. “Before this insect came, eucalyptus was insect-free--there wasn’t a pest that could harm it. That’s not true anymore.”

No Known Protection

Tree experts say there is no known pesticide that will protect eucalyptuses from the beetle, which burrows under bark and cuts off the supply of nutrients.

“They’re in stress from several years of drought conditions,” said Robert E. Johnson, head deputy forester for Los Angeles County. He said such weakened trees do not have sufficient sap pressure to keep the beetles out.

Officials said they are urging homeowners to begin “deep watering” trees to the limbs’ farthest drip line with a dribbling garden hose for 24 hours every few weeks.

Forestry experts said the 1 1/2-inch-long beetle can fly up to nine miles at night--putting it within striking distance of Southern California’s original eucalyptus grove in Canoga Park.

Four of those first trees still survive at the Shadow Ranch Park at 22633 Vanowen St. The 150-foot-tall giants were planted 115 years ago by pioneer West Valley rancher Albert Workman and are said to be the parent trees for most Southern California eucalyptus.

Australian Imports

Workman imported the eucalyptus seedlings by sailing ship from Australia in the early 1870s. Later, offshoots from Workman’s grove were cultivated as railroad steam engine fuel supplies and as windbreaks on ranches.

Ironically, say forestry experts, the eucalyptus beetle apparently smuggled itself into the United States 19 months ago in a load of eucalyptus lumber shipped from Australia to the El Toro area.

Los Angeles County officials first noticed the insect about six months ago, when eucalyptuses began dying in several county parks in the San Gabriel Valley.

The Sylmar infestation was discovered two weeks ago in three dead trees on a vacant lot next to a gas station at the intersection of Foothill Boulevard and Maclay Street. No beetles were found at the three trees, although insect burrows known as “galleries” were clearly visible between the bark and the hardwood. Telltale oval-shaped exit holes used by the emerging adult beetles were also found.

“The adults fly at night and are attracted to trees, where they lay eggs in bark crevices,” Rosser Garrison, entomologist with the Los Angeles County agriculture commissioner’s office, said Thursday.

“The eggs hatch, and young larvae bore into the wood. If the tree is healthy, the sap will flood the gallery and kill the insect. But, if it’s weakened, it continues to bore underneath the bark, in the cambium layer between the bark and the hardwood. A single beetle can girdle the tree,” he said.

Adults Emerge

As the larvae grow, they bore into the heart of the wood as well as back toward the bark. After about 10 days, the adult beetles emerge and fly out of the oval-shaped escape hatches, Garrison said.

Robert E. Johnson, head deputy forester for the county, said the beetle “is moving rapidly and killing a lot”--although no tally of dead trees is being kept.

Johnson said the infestation is accelerated by independent firewood sellers who move from place to place with wood chopped from infected dead trees.

“Eucalyptus is one of the better firewoods, and it’s transported throughout California,” he said. “There is no law that covers the treatment of infected wood.”

Infested Wood

Spitzer said owners of eucalyptus trees killed by the beetle should either bury the wood or pay a tree-trimmer to turn it into small chips to prevent unhatched beetles from escaping and spreading the infestation.

Trees cut into firewood should be sprayed with lindane, a pesticide used by professional pest control operators. The treated woodpile should then be covered with plastic for six months, Spitzer said. Johnson said the chemical dissipates within that period and poses no danger to those handling the wood.

He said distressed trees can be detected by viewing them through a photographer’s yellow filter. The leaves of drought-weakened trees look lighter than those of healthy trees.

Researchers at the UC Riverside who are studying the eucalyptus beetle plan to travel to Australia in two months to look for parasites and other natural predators that can be imported to combat the insect, a university spokeswoman said Thursday.

Eucalyptus Tree Owners’ Guide

Irrigate trees for 24 hours with a trickling hose to help head off infestation. If necessary, form dirt basins to hold the water.

If you see oval-shaped holes in the bark, your tree is infested and will die soon.

Immediately remove dead trees and destroy the wood or have it chemically treated by professionals before storing for firewood.

Source: Los Angeles County officials