Voracious Beetles Making Mincemeat of Eucalyptus Trees

A spreading beetle infestation that could threaten millions of eucalyptus trees in Southern California has prompted warnings from Los Angeles County officials against transporting eucalyptus firewood in the Los Angeles area.

“It’s a time bomb,” said Herbert Spitzer, a senior deputy county forester who discovered three beetle-infested trees in Sylmar in the San Fernando Valley two weeks ago.

“Before this insect came, eucalyptus was insect-free--there wasn’t a pest that could harm it. That’s not true anymore.”

Tree experts said there is no known pesticide that will protect eucalyptus trees from the Long Horned beetle, which burrows under bark and cuts off the trees’ nutrient supply. They said that trees that have been weakened by drought conditions during the last two years are vulnerable.

Because of that, officials are urging homeowners to immediately begin “deep watering” trees beneath limb drip lines by letting a dribbling garden hose run 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 early trees survive at the Shadow Ranch Park. The 150-foot giants were planted 115 years ago by pioneer rancher Albert Workman and are said to be the parent trees for most Southern California eucalyptus.

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

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

Since then, the insect has killed trees in Irvine, Riverside County and in the San Gabriel Valley, said Robert E. Johnson, head deputy forester for Los Angeles County.

Johnson said the beetle “is moving rapidly and killing a lot”--although no tally of dead trees is being kept.

“Once they are in the tree, essentially it’s a goner,” Rosser Garrison, entomologist with the Los Angeles County agriculture commissioner’s office, said Thursday.

“The adults fly at night and are attracted to trees where they lay eggs in bark crevices. 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.”

As the larvae grows, it forms a pupa and bores into the heart of the wood as well as back toward the bark. After about 10 days, the adult beetle emerges and flies out of an oval-shaped escape hatch.

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

Spitzer said owners of eucalyptus trees killed by the beetle should either bury the wood or have it “chipped” into small pieces by a tree-trimmer to prevent unhatched beetles from escaping.

Trees cut into firewood should be sprayed with Lindane, a chemical 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 tree owners can detect distressed trees by viewing them through a photographer’s yellow filter. The leaves of drought-weakened trees look lighter than those of healthy trees.