Oaks Under Siege : Bark-Burrowing Bugs, Squirrels, Drought Killing Historic Trees

Besieged by bark-munching beetles and burrowing ground squirrels, smothered by smog and weakened from eight years of drought, Chatsworth’s oak trees--many of them hundreds of years old--are dying a slow death, Los Angeles officials said this week.

“The oaks are croaking,” said Dennis LaFrance, tree surgeon supervisor at the Los Angeles Department of Public Works.

The Chatsworth oak trees are viewed both as a precious ecological resource and a vital part of the region’s history, drawing the protection of city and county ordinances that require replacement of oak trees that are cut down.

The trees have a special significance in the San Fernando Valley, which was once known as Valle de los Encinos-- the Valley of the Oaks. An oak known as the Lang Oak, located on Louise Avenue south of Ventura Boulevard in Encino, is believed to be 1,000 years old.

Officials now warn that two species--the California valley oak and the California live oak--are either dying or are in a state of “serious decline.”

“If nothing’s done, I’d give them maybe another 20 to 25 years of survival,” said Alex Costa, horticultural supervisor of the Los Angeles Department of Water and Power.

Though nearly all of Southern California’s trees are suffering because of lack of rainfall and heavy air pollution, Chatsworth’s oak trees are at particular risk, say officials. They are being attacked by “twig girdler” beetles--pests that bore through bark--and by ground squirrels that dig holes through the oak roots, allowing precious moisture to evaporate.

Man, the two-legged animal, also bears some responsibility for the trouble.

“Because of development, California oaks are becoming rarer and rarer,” said Lynne Plambeck, a Sierra Club member involved in local efforts to save oaks. “They are our native species and they provide acorns and sustenance for our native flora and fauna. Oaks once represented a major part of our local forest. They’ve been here for hundreds of years, and they’re meshed in our history. They have a special beauty and eloquence.”

Although city officials are particularly worried about oak trees in Chatsworth--about 60 oaks live on the dried-up Chatsworth Reservoir, which DWP owns--the problem reaches throughout Southern California.

“The problem isn’t just in Chatsworth, though it may be worse there due to the girdlers,” said LaFrance, the public works department tree surgeon. “Humanity is encroaching. People are over-watering their lawns and creating conditions ripe for oak root fungus. There’s air pollution. There’s really not much you can do besides control pests.”

DWP officials say they will not spray insecticides on the oaks without the permission of the community. Prompted by several residents worried about the oaks, DWP has scheduled a meeting Monday with the Chatsworth Coordinating Committee to discuss spraying the trees. The noon meeting, open to the public, will be held at the Chatsworth branch of the Glendale Federal Bank at 21821 Devonshire. Michele DeGaetano, a Chatsworth resident, said she noticed several months ago that the oaks in her neighborhood appeared to be dying. She called DWP and met with some department officials, who examined the trees and confirmed her fears.

Oaks in DeGaetano’s neighborhood, which is located near the Chatsworth reservoir, turned a sickly shade of rusty brown this summer, long before the fall season.

In an attempt to control the ground squirrels, DWP workers have been leaving poisoned bait--oats laced with a chemical called diaphacinone--then filling in the squirrel holes. The squirrels must ingest the chemical two to three times before it kills them and the risk of other wildlife dying from the oats is low, Costa said.

While the spraying of insecticides may have its critics, at least some Chatsworth residents said they don’t mind the treatment if the oaks can be saved.

“People liked the way it used to look around here,” said Dee Gould, a 21-year Chatsworth resident whose back yard borders the reservoir. “Nobody wants to see the oaks die. They’re brown and they look all dried up.”

If nothing is done, “the community will lose oxygen, its own heritage, valuable shade and a vital part of the ecosystem,” said Helen Treend, founder of the Oak Tree Coalition, which in the early 1980s helped draft the city’s oak tree ordinance geared at preserving some of the city’s oldest trees.

“It’s a serious concern, those oaks,” Costa said. “They’re awesome critters.”

Oak Trees at Risk The California valley oak and live oak trees at Chatsworth Reservoir and surrounding communities live under adverse conditions. In addition to pollution and drought, they are subjected to “oak twig girdlers,” beetles that eat their bark, and ground squirrels that dig through their roots. *

California live oak Quercus agrifolia Height: 30-80 feet or larger Trunk size: Two feet in diameter Bark: Dark, furrowed and checked Habitat: Grows mostly in thin, sandy, rocky soil in the mountains from southern Oregon to Southern California. Leaves: About two inches long, deeply lobed, ending in bristly points Longevity: Can live 800 years or longer *

Oak Twig girdler Agrilis angelicus Description: Small beetle, gray-brown in color to blend into bark Habits: Insect bores into bark of twigs, lays egg. Hatched larvae bore through center of twig, pupate and eat their way to surface. Cycle repeats. *

California valley oak Quercus lobata Height: 70 feet Trunk size: At least two feet thick Bark: Thick, light-colored ash gray, distinctly checked Habitat: Grows in deep, well-drained soil generally in valleys Leaves: Three to four inches long, deeply lobed, but its lobes are rounded Longevity: Can live 700 years or longer, average 400-450 years Source: Theodore Payne Foundation; Tree Life Concern Inc.