🚀 go-pugleaf

	If you're considering a vacation in California, you may
want to look this over -- lest you bring a blight back with you.

---------- Forwarded message ----------
Date: Fri, 28 Jun 2002 15:05:36 -0400

  Sudden oak death spreads quicker
  A recent test showed the microbe on the shoes of nine out of 10
  hikers leaving a Santa Cruz Mountains park
  By Lisa M. Krieger
  SAN JOSE MERCURY NEWS

          New scientific evidence indicates that the microbe behind
  sudden oak death is more widespread in infected areas than previously
  thought, raising fresh concerns about whether it will be possible to
  contain the deadly disease.
          Scientists are learning that the predator -- a fungus-like
  pathogen -- isn't confined to oaks. It's present in other plants and
  trees, though it doesn't always harm them, and in soils and streams.
          It also seems to move easily from one place to the next: A
  recent test at a Santa Cruz Mountains park found that nine out of 10
  hikers leaving the park had the microbe on their shoes.
          These findings complicate the murder mystery that haunts Bay
  Area forests. The disease is thought to have arrived only 10 or 15
  years ago -- but has already killed hundreds of thousands of trees,
  particularly in Santa Cruz and Marin counties.
  At a conference last week on forest invaders at UC Davis, scientists
  said it was unprecedented to have a pathogen spread across so many
  native plant species so quickly. Worried scientists are expanding
  their monitoring efforts, using genetic tests to study 5,000 to 6,000
  sick trees in the Bay Area.
          "It was transported in -- and can be easily transported out"
  of local forests, said plant pathologist David Rizzo of UC Davis.
          Sudden oak death is caused by a microbe called phytophthora
  ramorum; Phytophthora is Greek for "plant-destroyer." A relative of
  this fungus was responsible for the potato blight in Ireland in the
  1840s, and another species nearly killed off Scotland's soft-fruit
  industry in the 1920s. A strain of the same microbe introduced to
  Australia in the early 1900s transformed forests into grasslands.
          Scientists fear that sudden oak death will make its way out
  of California and infect the forests of the rest of the country. Lab
  tests show that eastern red oaks are susceptible. At the U.S. Army's
  research institute at Fort Detrick, Md., scientists are now studying
  the vulnerability of 20 eastern species.
          A new federal quarantine bans shipping soil and plants from
  more than a dozen host species from the 10 infected California
  counties. Canada has gone even further, banning imports of soil and
  host plants from anywhere in the state.
  In this woodland mystery, surprising new scientific evidence has
  absolved the lead murder suspect: oak trees.
          Research by Rizzo, forest pathologist Matteo Garbelotto of UC
  Berkeley and others shows that oak trees do not seem to transmit the
  microbe to other plants -- they are merely innocent victims. Oak
  trees are infected for as long as a year before they drop their
  foliage and die.
          The microbe travels to the oaks from other common woody
  plants, particularly the California bay laurel. In a botanical
  version of Typhoid Mary, it lives on these trees' leaves without
  killing them, then spreads by splashing onto adjacent plants during
  winter rainstorms.
          "These plants are just as much, or more, impacted as the
  oaks," said Rizzo. "And because some of its plant hosts do not die,
  the pathogen stays on the site."
  Disturbingly, the microbe also floats through the air, washes into
  the soil and floats in water. It needs water for part of its life
  cycle, thus spreads more readily during wet months and wet El Nio
  winters.
          In Big Sur's Big Creek Preserve, the disease is moving up the
  river canyons toward the ridgetops. In Yosemite National Park,
  scientists fear it will invade the damp Yosemite Valley, home to both
  oaks and bay laurels.
  Concern about spread of the disease has caused scientists to expand
  monitoring at local parks. Preliminary results from an ongoing study
  at Henry Cowell State Park in the Santa Cruz County town of Felton
  found evidence of the microbe on the muddy shoes of about nine out of
  10 hikers as they exited the park. Scientists say this does not mean
  that this particular park has a unique problem -- just that the
  microbe is widespread in this type of forest and that hikers and
  bikers must be vigilant to rinse their shoes and tires.
          Scientists still don't know exactly how or where the disease
  got started.
  A lead theory is that the microbe was brought into the region on
  rhododendrons, a popular nursery plant that carries the microbe
  without killing it.
          It is thought to have arrived relatively recently. Genetic
  analyses of many microbial specimens show that they are genetically
  almost identical, meaning that they have not been around long enough
  to mutate and create genetic diversity in their populations.
          But the microbe has quickly spread to a variety of
  microclimates and forest types. It has been found as far south as Big
  Sur, north to the Mendocino town of Boonville and east to the Solano
  County intersection of Highways 80 and 680. An outbreak in the town
  of Brooking, Ore., is thought to have been eradicated. Along the
  Ocean View Trail in Muir Woods, almost every tanbark oak is infected.
          It is most prevalent in the mixed evergreen forests that are
  a major part of the Bay Area landscape, where almost every species of
  woody plant is at potential risk, according to Rizzo.
          "We've been concentrating on the oaks -- and were surprised
  to learn its broader total impact on the forest," said Rizzo. Contact
  Lisa M. Krieger at lkrieger(at)sjmercury.com or 408-920-5565.

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