Torrey Pines Imperiled by Beetle Pests, Experts Say

The gnarled but picturesque Torrey Pine tree, the rarest species of pine in the United States and a revered part of the coastal landscape just north of La Jolla, have been jealously guarded from human harm here like a jewel in a vault.

But now the Torrey Pines that cling to a 4-mile stretch of sandstone bluffs face a new threat. Weakened by two years of drought and several days of hellish heat in late summer, they have been hit by a bark beetle infestation which, if unchecked, could seriously deplete the Torrey Pines State Reserve.

The pest, called the “confused five-spined beetle” because of the aimless path it bores under the bark of a tree, has already killed a dozen Torrey Pines at the 1,750-acre park and threatens to lay low more than 100 others. State officials worry that the problem could spread even further into the park’s Torrey Pines population, estimated at 7,000 trees.

Source of Concern

“We’re deeply concerned and a bit alarmed at the extent of the infestation,” said Bob Wohl, supervising ranger at the reserve. “It’s located in the heart of the park, the areas with the highest visibility and the most prominence.”

Aside from the pines along the San Diego County coast, the trees exist in only one other place in the world--on Santa Rosa Island, one of the chain of Channel Islands southwest of Santa Barbara.

State parks officials are hopeful that rain will continue through the winter, bolstering the health of the pines and increasing the production of sap that typically wards off the pests.

“We hope the rain we’ve had since Thanksgiving Day and the tremendous drop in temperature will knock the beetles off,” Wohl said.

Plans for Counterattack

If the pests are still prevalent by spring, however, authorities probably will begin a counterattack, even though park policy encourages a laissez faire management approach to help maintain the reserve’s ecosystem.

Bill Tippets, a state park ecologist, said officials would probably begin by thinning out unhealthy trees. Bark on infested pines probably would be stripped to create an inhospitable environment for the beetles. If necessary, some of the affected pines might be cut up and hauled out of the forest.

Authorities suspect that some weakened and fallen trees have served as incubators for the infestation.

Insecticides would be considered only as a last resort. Tippets said chemicals typically prove only partly successful and could potentially kill insects that may prey on pests like the beetle.

The beetle, Ips paraconfusus, hardly looks like a feared invader. Less than a quarter-inch long, the insect has a dark brown body with tiny rounded antenna. The slow-moving, winged insect is capable of wandering among several trees during its lifetime.

Effects of Insects

It devours the cambium layer, the thin coat between the bark and inner hardwood that serves as the circulatory system for the tree, processing photosynthetic products as well as nutrients tapped from the ground.

A male finds a susceptible tree--typically one weakened by drought or aging--and sends out a sex attractant that lures female beetles. Together, they hollow out a larval chamber in the tree where the female lays eggs. The hatched larva do most of the damage.

Clusters of needles that characterize the Torrey Pine begin to drop. If the larva circumnavigate the trunk, severing the cambium layer connecting roots and branches, the pine eventually will die.

On a tour of the grove, Wohl pointed to a graying tree. Reaching up, he grabbed a small branch and with an easy twist pulled off a ring of bark, ready proof that the tree had been infested.

“I would say what we’re talking about here is a doomed tree,” he said.

Problems Noted

Wohl said rangers first noticed problems in April, when the needles on several trees began to brown and drop off. The problems persisted through the summer and Wohl said several days of 100-degree temperatures produced a “blast furnace effect on the trees.”

By Labor Day, experts had isolated the beetles as the problem. In mid-December, a state forest pathologist conducted tests. He agreed that the drought had weakened the trees enough to allow the beetle infestation.

Much like the battle between a human immunological system and foreign bodies, Torrey Pines fight a continuous war with the beetle and other pests. A healthy flow of sap serves to repel the invading hordes, pushing their eggs out or encasing an attacker in a coat of resin.

“The bark beetles are always here, but the trees can normally repel them,” Wohl said.

The problem has spread to several of the most prominent spots in the park that feature some of the oldest and most beautiful pines, which can live about 300 years. Beetles also have spread to several trees surrounding the park headquarters.

Given a New Name

Once known as the Soledad Pine, the trees were renamed in 1850 by Dr. C.C. Parry, a botanist for the U.S. Mexican Boundary Survey. Parry chose the botanical name, Pinus torreyana or Torrey Pine, in honor of his former botany professor, Dr. John Torrey.

In 1883, Parry returned to the site and began urging that the land be acquired to preserve the species from what he feared would be certain extinction at the hands of man. The City of San Diego designated 369 acres as a public park in 1899.

Ellen Browning Scripps acquired adjacent groves in the years that followed, and those lands were added to the park in 1924, when it was enlarged to nearly 1,000 acres. In 1979, a 154-acre extension area was formed on the sloping hillside to the north of Los Penasquitos Lagoon.

There have been numerous infestations. Most recently, bark beetles killed 18 trees in 1984 and 1985. Eventually, rains helped bolster the surviving trees, and they repelled the beetles.

Some authorities suggest that the Torrey Pines State Reserve’s trees have been weakened not only by the recent drought, but by increased competition for water among the proliferating pines.