Capitol Alert

Bark beetles empowered by drought threaten rare Torrey pines

The famous Torrey pines at Torrey Pines State Natural Reserve in San Diego are being hit hard by bark beetles and drought conditions, which have made the trees especially vulnerable over the past few years.
The famous Torrey pines at Torrey Pines State Natural Reserve in San Diego are being hit hard by bark beetles and drought conditions, which have made the trees especially vulnerable over the past few years. Special to The Bee

The rarest American pine tree, sinewy branches full of needles and cones, towers in clusters along the sandy trail of Torrey Pines State Natural Reserve.

Then, three bare, brown trees droop on a nearby slope. And then another – its trunk a mere ghostly shell – perches above a canyon.

That tree “will eventually fall into the canyon,” said Darren Smith, district services manager for the San Diego Coast District of California State Parks.

The reserve has many Torrey pines with round, healthy canopies. But lifeless skeletons of once vibrant trees pepper the trail. They are dead or near death.

“They’re little beetle-incubators,” Smith said of the dying ones. “They’re weak and already messed up.”

State park officials are concerned about the effects of the state’s drought on the trees their namesake reserve is intended to protect. The dry conditions have weakened trees, making them unable to fight bark beetles that have infested and killed dozens of trees at the reserve. To help combat the problem, state park officials have expanded trapping efforts in hopes of treating sick trees and isolating the infestation.

So far, about 150 of the reserve’s roughly 4,600 Torrey pines have been affected, Smith said. Of those 150 trees, about 100 have been removed in the last year, but the rest remain. Removing them may be too destructive or hazardous, particularly if the tree is on a slope or cliff.

To prevent other trees from becoming infested, park officials have added more black funnel traps to capture the beetles. The nontoxic traps are designed to look like broken tree limbs and contain simulated beetle pheromones to attract the insect, said park ecologist Charlie Kerns, who regularly monitors the trees and traps.

The trapping program is not new for the reserve, but in recent months, the number of beetles caught has increased from a steady average of 500 a week to about 3,500 a week, Kerns said.

Beetles have become a chronic worry.

“This is beetle nirvana,” Kerns said. “They get to live year-round.”

Kerns collects the beetles in plastic baggies and places them in a park freezer, both so he can count the beetles and know more about the types in the trees. Smith hopes that entomologists will study them to learn more about what’s happening at the park. In the late 1980s, about 840 trees were lost due to the Ips paraconfusus – a beetle that is part of the current infestation, he said.

In another spot, Kerns finds a dead red turpentine beetle that drowned in a Torrey pine’s red sap – the way in which the trees are supposed to fight off the beetles.

Torrey pines only grow naturally in two places: the Torrey Pines State Natural Reserve and Santa Rosa Island in the Channel Islands National Park – about 25 miles offshore of the city of Santa Barbara. The island harvest is expanding, said Yvonne Menard, park spokeswoman. There are about 3,000 mature trees with thousands of young trees expected to grow fully, she said.

Trees in the wild generally can grow as tall as 60 feet and live an estimated 100 to 150 years, according to “Trees of the California Landscape: A Photographic Manual of Native and Ornamental Trees” by Charles R. Hatch.

Part of what makes the trees so special is their ability to thrive in a dry climate, said Joe McBride, professor emeritus of forestry at UC Berkeley.

“It is able to grow in these really hot, low rainfall areas,” McBride said. “This is an example of a tree that is adapted to the changing climate.”

Nonetheless, the extreme dry conditions of the last few years have taken their toll.

Torrey pines naturally have resin that protects them and pushes insects out from their bark. Under drought conditions, the trees produce limited resin, McBride said.

The trees are important because they can help provide shading of housing and streets, reducing air conditioning usage. Additionally, the trees may provide wildlife habitat for certain birds and mammals, McBride said.

“And they have a real potential for contributing to the beauty of the urban landscape,” McBride said.

The California Native Plant Society, a nonprofit dedicated to saving and celebrating the state’s native plants, has designated Torrey pines as endangered since 1971, said Dan Gluesenkamp, the society’s executive director.

“The Torrey pine is a very special plant – very charismatic,” Gluesenkamp said. “It’s a part of California’s ancient history that’s still here, and yet it’s so precarious.”

Journalist Marisa Agha is based in Southern California.