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Posts Tagged: Phytophthora ramorum

Coast redwoods increasingly susceptible to fire damage

Fire consumes a once-healthy California redwood tree. (photo: USFS)
California’s renowned coast redwood trees, previously believed to be fireproof, are now more than four times more susceptible to wildfire injury in coastal forest areas infested with the sudden oak death pathogen. These redwoods are now as susceptible to wildfires as other trees.

Millions of trees, including tanoaks, coast live oak, California bay laurels, and many other forest species have been killed by sudden oak death in coastal areas of central and northern California, and Oregon. The pathogen, Phytophthora ramorum, was first linked to the massive tree death in the mid-1990s.

David Rizzo, professor in the Department of Plant Pathology at UC Davis, and his research team are studying how the coastal forest ecology is changing since sudden oak death appeared, and why coast redwoods (Sequoia sempervirens) are subsequently so much more susceptible to fire.

It is the presence of the sudden oak death pathogen in forests that poses heavier fire risks for redwoods.

“If redwoods didn’t live in forests affected by the disease, they could withstand fires just fine,” says Margaret Metz, a postdoctoral research scholar working with Rizzo.

Professor David Rizzo, UC Davis.
An initial explanation for the higher redwood mortality following wildfires is heavier fuel loads (such as fallen, dead branches from tanoaks) in forests affected by sudden oak death. Tanoak, Notholithocarpus densiflorus, is the primary host dying from sudden oak death and the main source of pathogen inoculum.

According to Rizzo, “The disease likely created more fuel for wildfires as dead tanoak branches fell. The loss of the oaks also would have decreased the amount of shade, drying out the forest and turning it into a tinder box, one not even redwoods could survive.”

A real key, though, is the finding that dead tanoaks, still standing, carry flames high into tree canopies, scorching the crowns of adjacent redwood trees. It’s this crown injury that is believed to have caused so many redwood trees to die in a number of fires that occurred in 2008.

Dead tanoaks in a redwood forest in the scientists’ California study area, pre-fire. (photo: Kerri Frangioso/UC Davis)
“Humans are causing widespread changes throughout our world, including greater wildfires related to changing climate and from increasing infectious disease due to more modes of transportation,” said Sam Scheiner of the National Science Foundation, which funded some of this research.

Rizzo, noting that an increase in fire severity is resulting from climate change and global movement of species, says, “There may be all sorts of consequences, among them, dead and dying coast redwoods.”

Additional information:

  • California's iconic redwoods in danger from fire and infectious disease. National Science Foundation report on Rizzo group’s work, August 2013
  • The effects of sudden oak death and wildfire on forest composition and dynamics in the Big Sur ecoregion of coastal California. General technical report
  • Ecology research article, Ecological Society of America
  • California Oak Mortality Task Force website
Posted on Wednesday, September 4, 2013 at 7:21 AM

UC Berkeley scientist surprised by SOD incidence

The Forest Pathology and Mycology Laboratory at UC Berkeley used 10,000 tree and plant samples collected by 500 citizens between April and June to document a dramatic increase in the Sudden Oak Death infection rate from Napa to the Carmel Valley, according to the San Francisco Chronicle.

"We found that the number of positives were double and in some cases triple what they were last year," said Matteo Garbelotto, the UC Berkeley forest pathologist who organizes the annual surveys. "We were surprised. That was a big jump."

Old Farmer's Almanac: 220 years of useful advice
Sam McManis, Sacramento Bee

The Sacramento Bee ran a feature story yesterday about the 220-year-old "Old Farmer's Almanac." The article said that most readers of the publication these days are not farmers. When the Bee contacted the California Farm Bureau Federation to find farmers who use the almanac as part of their work or even just for entertainment, its spokeswomen suggested asking Chuck Ingels, farm advisor and director of UC Cooperative Extension in Sacramento County.

"I honestly have never looked at the almanac, but I've seen it on bookshelves," Ingels said. "It's never mentioned by the farmers I'm in contact with."

Dramatic increase in Northern California Sudden Oak Death.
Dramatic increase in Northern California Sudden Oak Death.

Posted on Monday, October 3, 2011 at 8:37 AM

Sudden Oak Death appears in San Francisco's Presidio

A coast live oak tree on the southeastern edge of the Presidio National Park in San Francisco was found to have Sudden Oak Death disease, according to an article in the San Francisco Chronicle.

The disease was believed to have made its way to the tree from an ornamental plant at a nearby home, reported Matteo Garbelotto of UC Berkeley's Forest Pathology and Mycology Laboratory. Scientists are concerned about the find because it means the microbe escaped from an ornamental and infected a wild tree despite an intensive nationwide effort to control the disease in nurseries.

“I was surprised by the finding because the Presidio is located in an urban setting, far from any other known infestation,” Garbelotto was quoted in a news release from the California Oak Mortality Task Force. “With a few exceptions, all known infestations are close to oak woodlands or redwood forests.”

The infected oak is one of the few native trees in the Presidio, wrote Chronicle reporter Peter Fimrite. Of the 60,000 trees in 300-acre park, only about 200 are native oaks.

The infected tree was discovered by an arborist for the Presidio Trust. The Garbelotto lab took samples, which showed a strain of sudden oak death that is normally seen only in ornamental plants. Laboratory workers tested other trees, plants and soil samples from the same area, but no evidence of the pathogen was found.

Garbeletto told the reporter the find should serve as a wake-up call across the United States.

"People's ears should go up in states where they have it in nurseries but not in the wild," he was quoted. "It shows that it can escape."

The Presidio Trust will be conducting a "SOD Blitz" April 29 to May 2, when hundreds of samples will be taken throughout the Presidio and vicinity. Training for the cooperative effort to sample for the pathogen will be provided by Garbelotto on Friday, April 29. Residents near the Presidio have been invited to participate in the training as well as follow-up sampling efforts on their properties. For more information, see

Camellia leaf infected with the pathogen that causes Sudden Oak Death.
Camellia leaf infected with the pathogen that causes Sudden Oak Death.

Posted on Thursday, March 31, 2011 at 9:11 AM

Berkeley lab tracks Sudden Oak Death with citizen help

Scientists at UC Berkeley are using tree and plant samples collected by citizens over the past two years to document Bay Area infestations of Sudden Oak Death, reported the San Francisco Chronicle.

"Last year we had about 240 participants and collected over 1,000 samples. These results were placed on a map so people can see where the positives are," UC Berkeley forest pathologist Matteo Garbelotto was quoted. "This is part of the solution. If we educate and involve individual property owners, we can make a really big difference."

The UC survey documents the following SOD spread:

  • In Atherton, Oakland, Hercules and Mill Valley
  • In Hercules-Pinole area, Orinda, Moraga and in Redwood Regional Park, Wildcat Canyon and Tilden Park
  • Creeping toward south Oakland
  • Recolonizing the Berkeley campus after it was thought to have been eliminated nine years ago
  • Moving southward and eastward along the Peninsula, infesting Woodside and Los Altos
  • All over Tamalpais Valley in Marin County
  • West of Healdsburg and Windsor in Sonoma County
  • In several trees on the edge of Carmel Valley Village
Garbelotto told reporter Peter Fimrite that Carmel Valley Village is a prime area for the disease to explode.

"The houses themselves are in the forest, so I can really see some potentially dangerous consequences," Garbelotto was quoted. "The people there don't really know what is going to hit them."

UC Berkeley Forest Pathology and Mycology Laboratory organizes eight meetings a year it which it trains residents to identify and deal with sudden oak death. Sign up to participate online.

Discoloration characteristic of infection by Phytophthora ramorum, which causes SOD.
Discoloration characteristic of infection by Phytophthora ramorum, which causes SOD.

Posted on Wednesday, October 6, 2010 at 10:28 AM

Volunteers battle Sudden Oak Death

To better understand the extent of sudden oak death in California, UC Berkeley professor Mateo Garbelotto is enlisting volunteers in "SOD blitzes" to scour neighborhoods and wildlands for symptoms of the devastating disease, according to a story in the Oakland Tribune.

Sudden oak death, caused by a fungus Phytophthora ramorum, has resulted in widespread dieback of coast live oak, California black oak, Shreve oak, tan oak and canyon live oak in Central and Northern California and Oregon coastal areas.

The Oakland Tribune article, written by Jonathon Morales, said the blitz isn't comprehensive or scientific, but Garbelotto believes the volunteers' efforts are helpful. The SOD blitzes inform and educate the community about Sudden Oak Death, get locals involved in detecting the disease, and produce detailed local maps of disease distribution.

"If you were to think, 'Oh, I know where sudden oak death is' and you're using data that was produced two years ago, probably you actually don't have a good idea where it is," Garbelotto was quoted.

The blitzes also benefit property owners by letting them know whether their own trees are infected. If detected early, Garbelotto said, there's a chance a property owner can save the tree.

Blitzes are scheduled for April and May. Dates, locations, contact information and reports on previous blitzes are on Garbelotto's Forest Pathology and Mycology Lab Web site.

A Big Sur tan oak that succumbed to sudden oak death.
A Big Sur tan oak that succumbed to sudden oak death.

Posted on Friday, April 16, 2010 at 7:33 AM

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