some news on sudden oak death plaguing the SF Bay Area
- To: m*@ucdavis.edu
- Subject: some news on sudden oak death plaguing the SF Bay Area
- From: S* A* O*
- Date: Fri, 09 Mar 2001 14:09:45 -0800
The following was posted to the CA-Natives listserv this morning. Good
news about this horrible problem that has been sweeping through parts of
California.
Sean O.
March 9, 2001
By MARY CALLAHAN
THE PRESS DEMOCRAT
In the first promising news since scientists began tracking the deaths
of tens of thousands of Northern California oaks in 1995, researchers in
Sonoma County have identified a potential treatment.
Testing over the past seven months indicates a substance used to combat
a fungus in avocado trees also helps infected oaks, UC Berkeley pathologist
Matteo Garbelotto said.
"This is just a basic first step," Garbelotto said Thursday. "It's not
like we have a cure. But it's a first step that is really significant
because it's going in the right direction."
Garbelotto will present his findings today at a conference on sudden oak
death in Marin County, which is considered ground zero for the pathogen now
known to affect coast live oak, black oak, Shreve's oak and tan oak, as
well as California huckleberry and rhododendrons.
The fungus, called a Phytophthora, is related to the species that caused
Ireland's 19th century potato famine. It has been found in trees from Big
Sur to Sonoma County, and as far inland as the Sonoma-Napa County border.
Just weeks after Garbelotto and a UC Davis scientist isolated and
identified the pathogen that's been killing oaks for a half-dozen years,
Garbelotto and a team of researchers started experimenting with potential
treatments in Petaluma.
They applied four substances, including a water-based control substance, to
90 potted trees infected with the sudden oak death fungus, he said.
The most successful, a phosphorus- and potassium-based fertilizer called
Phosphonate, reduced the size of cankers on the infected trees by an
average 75 percent, Garbelotto said.
"In terms of area, it was about a 15-fold reduction," he said.
Garbelotto said he chose to experiment with a fertilizer in part because
of its success with avocado trees and because the disease-causing pathogen
can't develop a resistance to it.
Phosphonate also lacks the toxic properties of a fungicide and "would
have better consequences for the environment," he said.
But it doesn't kill the microbe that causes sudden oak death. Instead it
contributes to the vigor of the tree and helping it battle the bleeding
lesions the fungus brings on.
A second chemical, used in the tests, a fungicide called Metalaxyl that
has been somewhat successful in treating potatoes, shows promise in
actually killing the fungus in the lab, Garbelotto said.
It reduced the size of lesions, too, though not as successfully as
Phosphonate.
Unfortunately, the oak fungus, if treated with Metalaxyl, could develop a
resistance that would render the fungicide ineffective, he said.
"It may be in the end a combination of the two may be the most effective
treatment," Garbelotto said.
Scientists will continue tests using the two substances, as well as
others, to pinpoint how they work -- and how they work best.
The federal government recently set aside $3.5 million for research,
monitoring and management efforts related to sudden oak death.
State and federal funds totaling $1.6 million already have been
allocated to help fight the disease.
The California Oak Mortality Task Force, formed last August, has
estimated $10 million is needed over the next two years.
Researchers tried several different applications for the recent
experiments, but injection so far works best and has fairly low
environmental impact because it delivers the chemical directly into the
tree, Garbelotto said.
The trees, tested at an undisclosed location in Petaluma under what
Garbelotto called "pretty rigorous conditions," were all about five to
seven years old, standing about 9 feet to 14 feet, he said.
By infecting the trees in August and then again in November, researchers
were able to simulate young and old cankers, he said.
Though the treatment worked best on the younger lesions, "we still got
significant control in the older cankers," Garbelotto said.
"That could be a good indication that the earlier we catch them, the
better," he said.
h o r t u l u s a p t u s - 'a garden suited to its purpose'
Sean A. O'Hara fax (707) 667-1173 sean.ohara@groupmail.com
710 Jean Street, Oakland, CA 94610-1459, U.S.A.
