Evergreen Trees Fall--Victims of Fungus

Evergreen trees in national parks from Lassen to Yosemite and Sequoia are dying from a chronic fungus that rots out roots, UC and U.S. government scientists said Monday.

The disease is spreading so fast in Yosemite National Park that most of the conifers in the densely covered six-square-mile valley floor will be dead within 40 years and replaced by oak, said John R. Parmeter Jr., a plant pathologist at the University of California, Berkeley.

Jack Moorehead, Yosemite park superintendent, said the root rot problem is most serious in the valley floor, which is just a small section of the 760,000-acre park. Even so, Moorehead does not see it as a threat to all the conifers in the valley.

The root rot has become so significant that National Park Service officials this summer allowed logging of some pine, cedar and fir trees, prompting complaints from campers in the heavily used park.

But the university research group headed by Parmeter had suggested the selective logging to try to slow the spread of the disease, known as Fomes annosus , and avoid accidents.

Weakened and diseased trees have blown down and been blamed for half a dozen deaths in the last 15 years, said Dick Smith, a U.S. Forest Service pathologist who heads a unit that detects and controls disease and pests on federal lands in California.

The problem extends far beyond Yosemite. Parmeter and Smith called it among the most serious disease problem facing the U.S. Forest Service and National Parks Service.

The Forest Service estimates that at least 15% of the trees lost yearly in California to disease and pests die because of Fomes annosus , and the toll is rising. Officials and plant pathologists said the damage may be far greater.

“We just don’t have a precise handle on the amount of damage. We know it is considerable,” said Bill Otrosina, a Forest Service pathologist in Berkeley.

In Sequoia National Park, about 20 giant sequoias have fallen in recent years because of the problem, and in the Cannel Meadows area of Sequoia as much as 60% of the stumps are infected.

Also hit hard have been trees near Big Bear Lake, the Table Mountain section of Angeles National Forest and the Laguna Mountain area of Cleveland National Forest, Smith said.

Also in Southern California, half a dozen campsites in Barton Flats are without trees. The problem extends north up the eastern slope of the Sierra, where the particular pine species there is especially susceptible to the malady. The problem also has been noted in Lassen Volcanic National Park.

“Once it’s there, there is nothing we can do but watch it,” Smith said.

The disease, first identified in the late 1960s, spreads when the roots of an infected tree touch another’s roots. Once a tree is infected, it will die within three to five years, Smith said. The death often is hastened because the tree becomes weakened and more susceptible to insect attack.

Because the fungus attacks trees more readily when they have been cut, the Forest Service now requires stumps left by logging operations to be treated with borax, which serves as a pesticide.

Parmeter believes the disease always has been present in Yosemite but that Indians used to burn the trees to maintain open oak woodlands for acorn harvests, a practice that kept the evergreens scattered.