Sudden oak death examined

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December 18, 2002
By BEN SHOUSE
Sentinel Correspondent

U.S. Rep. Sam Farr on Tuesday kicked off the largest-ever
conference on sudden oak death, a tree disease that is scarring the
landscape of the Central Coast.
Rarely does a small conference among tree-disease experts garner
Congressional attention, but this is no ordinary disease. Since its
discovery in 1995, the disease has killed hundreds of thousands of
trees, leaving enormous bald spots in oak forests from Big Sur to
Sonoma County.
It was recently found in at least 4 percent of redwoods in Henry
Cowell Redwoods State Park. Those trees are infected but the disease
is not killing them, as it is oaks.
“It really is the season to talk about trees,” said Farr, D-Carmel.
He praised the roughly 300 researchers for their efforts, but said they
must fight to keep their research budgets.
“Sudden oak death (research) is new on the radar screen, and the
only thing that keeps it going is pressure from the public,” he said.
“Be that squeaky wheel,” he said, urging scientists to publicize their
fight and not just talk to each other.
The science presented at the conference suggested cuts to research
budgets could not come at a worse time.
Very little is known about the way the disease organism, a
fungus-like microbe called Phytophthora ramorum, spreads over long
distances or what can be done to stop it.
And what is known is not good. The organism displays the sinister
calling card of an aggressive invader: the majority of the killer
microbes are genetically identical, they kill in just a few years, and
they infect more than 20 species.
And if El Niño brings wet weather this year, that could enhance the
growth and spread of the mysterious killer, said David Rizzo, a plant
pathologist at UC Davis.
But that’s assuming the disease acts like its many cousins in the
genus, which includes “late blight,” the cause of the Irish potato
famine. And so far it has defied that assumption fairly regularly.
The disease travels short distances in splashing rainwater. New
research presented Tuesday also suggests it may travel in stream
water, underground through soil, or on the boots of hikers. But one of
the big mysteries is how it moves over medium distances, and why it
infects some areas and not others.
For example, the disease is common at Henry Cowell, but not at Big
Basin State Park, Rizzo said.
Answers will have to wait for more research results, and so will
homeowners and nature lovers hoping to fight the disease.
Lab studies have found a pesticide containing phosphoric acid can
cure trees by injection. But an effective treatment still must undergo
testing to prove acceptable to the California Department of Pesticide
Regulation, said UC Berkeley pathologist Matteo Garbelotto.
Even if the treatment is approved, it would be costly and difficult to
apply to wilderness areas. A cheaper option might be aerial spraying,
but that would have to undergo much more extensive testing for
environmental impacts and would likely face public disapproval.
Federal funding cuts would only add to those woes, Garbelotto said.
On the other hand, hundreds of scientists are now working on the
disease where there were only a handful three years ago.
Said Farr, “They’re getting major funding. Others should be so lucky.”

The Sudden Oak Death Science Symposium concludes today.