Beetles, Fungus Killing California Oaks
12/16/99
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Title: Beetles, fungus killing California oaks
Source: The Associated Press
Status: Copyright 1999, contact source for permission to reprint
Date: December 16, 1999
An army of beetles and a predatory fungus have been killing off
natural habitats and picturesque landscapes created by native oaks,
the most common trees in California.
About 30,000 of the coast live oak and its cousin, the tanoak, have
died in recent years, said Bruce Hagen, an urban forester with the
California Department of Forestry.
"I'm sure it's part of the natural scheme of things, but there's no
historical record of this occurring before," Hagen said. "It's really
a strange and kind of unexplained phenomenon at this time."
Researchers believe the combination of drought in the mid-1980s and
early 1990s followed by heavy rain from El Nino between 1997 and 1998
may have caused "stress" in native oaks, leaving them susceptible to
bark-eating beetles and damaging fungus.
"The bottom line with trees and people is that if you have a lot of
stress, you'll get some disease and problems," Hagen said.
Roots mired in soggy soil can lead to hypoxlyon fungus, which in turn
attracts bark beetles to the trees, said Larry Cooper, spokesman for
the state Department of Food and Agriculture.
"The female beetle bores into the tree and sends out a pheromone that
attracts other beetles," Cooper said. "And they attack the tree until
it's dead."
Bark beetles, which are about the size of fleas, typically move in
first and are followed by the rice-sized ambrosia beetle that feasts
on fungus, Hagen said.
The beetles and fungus can destroy a tree in about two weeks.
The oaks, which have a life span of 250 to 300 years, have little use
as lumber, but are valued by property owners for aesthetic reasons.
The silhouette has become an emblem of sorts for California and the
trees also have become the namesake of several cities.
The native oaks, which are found mostly on private land, also provide
habitat for more than 300 species of animals and more than 5,000
insects and other invertebrates, said Bill Tietje, a natural
resources specialist with the University of California Cooperative
Extension in San Luis Obispo.