Ancient Oak’s Bark Is Worse Than Its Blight

Famed arborist Dr. Alex L. Shigo poked the patient’s bark with two metal prongs and concentrated on the digital readout that would help him with his diagnosis. He then announced that the landmark 1,000-year-old Lang oak tree will shade Encino residents for many more generations to come.

“You’ve got a remarkable tree here,” said Shigo, an arborist from Durham, N.H., who was a top scientist for the U.S. Forest Service for 26 years. “The less you do to this tree the better it’s going to be.” Shigo was in town to address a group of tree surgeons at the L.A. County Arboretum in Arcadia.

The tree, a California live oak, is south of Ventura Boulevard in the middle of Louise Avenue. The tree’s trunk is 24 feet around and its thick canopy of branches is 150 feet across.

Shigo diagnosed the tree Friday with a “Shigometer,” a device named in his honor that measures the tree’s resistance to electrical currents. Current readily passes through a healthy tree.

Using the car stereo-sized device, Shigo determined that the east side of the tree’s trunk has been ailing for as long as 15 years and that a 10-square-foot patch of bark should be removed to make it well. Once the bark is removed the wood should be cleaned to rid the trunk of the burrowing insects that are weakening it, Shigo said.

“What the bark is doing now is protecting the insects,” Shigo said.

He also prescribed trimming unhealthy branches that have sprouted near the tree’s top. The leaves on those branches “lack luster and they lack size compared to the leaves on the lower branches,” Shigo said.

He said tree’s illnesses are probably a result of damage to the roots on the tree’s east side from road construction projects.

Controversy over the tree’s health sprouted in April of 1991, when free-lance arborist Robert Wallace said the tree suffered from slime flux, a tree ailment that can be deadly. Wallace prescribed chiseling small holes in the bark to release the toxic sap that he said was slowly killing the oak.

Shigo disagreed. He said the slime, though not healthy for the tree, has actually helped to protect the tree from decaying.

He said the tree told a different tale.

“I think this tree is saying, ‘I have lived here a long time and I deserve the respect and I deserve dignity, so when I get sick don’t inject me with spikes and don’t start doing heroic things to me,’ ” Shigo said.

On a more positive note, Shigo had high ratings for the oak’s soil.

“It’s excellent soil for this tree,” Shigo said. “It’s porous and so it’s able to hold moisture and it’s filled with earthworms.”

Shigo’s diagnosis came as a relief to Bob Kennedy, superintendent of the city’s street tree division.

“I feel great comfort that he feels we’re on the right track,” Kennedy said.

The bug-infested portion of the tree will be removed next week by three tree surgeons from the city’s street tree division, Kennedy said. But the unhealthy branches won’t be removed until March or April.

What if the prescription proves unsuccessful and the tree dies?

“I’ll probably look for another job,” Kennedy said.