Re: some news on sudden oak death plaguing the SF Bay Area
What a pity there doesn't seem to be more international link-up between
botanists or plant pathologists or whatever. Here in Western Australia we've
been using phosphonate or phosphonic acid for the phytophthora infecting our
native plants for quite a number of years. More and more uses are found for
it all the time, and it's a comparatively benign fungicide I believe.
Margaret Moir
Olive Hill Farm
Margaret River, Western Australia.
www.wn.com.au/olivehill
----- Original Message -----
From: Sean A. O'Hara <sean.ohara@groupmail.com>
To: <medit-plants@ucdavis.edu>
Sent: Saturday, March 10, 2001 6:09 AM
Subject: some news on sudden oak death plaguing the SF Bay Area
> 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.
>
>
