Sudden Oak Death linked to rhodendrons
- To: "medit-plants"
- Subject: Sudden Oak Death linked to rhodendrons
- From: J*
- Date: Thu, 11 Jan 2001 18:52:02 -0800
I found this news release extremely interesting; has ramifications galore.
-----Original Message-----
From: Julie K Nelson/R5/USDAFS <jknelson@fs.fed.us>
To: jaknelson@shastalink.k12.ca.us <jaknelson@shastalink.k12.ca.us>
Date: Thursday, January 11, 2001 8:54 PM
Subject: Sudden Oak Death
>
>http://www.berkeley.edu/news/media/releases/2001/01/10_oak.html
>
>UC researchers announce results that could complicate measures to
> halt spread of Sudden Oak Death
> 10 Jan 2001
>
> By Catherine Zandonella, Media Relations
>
> Berkeley - A common nursery plant may lead to
>increased complications
> and possible new management practices in the
>fight to halt Sudden Oak
> Death, a highly contagious fungal disease that
>is killing California oak trees,
> University of California researchers announced
>today (Wednesday, Jan.
> 10).
>
> In a breakthrough in the study of the disease,
>UC researchers discovered
> that the rhododendron, a popular ornamental
>plant, can be infected by the
> same fungus that is causing the oak disease.
>The fungus has infected
> European rhododendrons and, as of yesterday,
>the researchers confirmed
> that it also is affecting California
>rhododendrons, suggesting a
> transcontinental link. Finding this relatively
>new fungus in two different
> parts of the world - and in two species - is
>unusual, the researchers said.
>
> The rhododendron discovery gives insight to the
>potential origin and
> transmission of this pathogen and may suggest
>new ways of spread.
> Previously, the pathogen only was known in
>three other California oaks -
> tanoaks, coast live oaks and black oaks.
>
> "We now know we have a host that could have
>carried the fungus a long
> way," said Matteo Garbelotto, a plant
>pathologist and adjunct professor in
> the Department of Environmental Science, Policy
>& Management in UC
> Berkeley's College of Natural Resources.
>"People don't really export oak
> trees across state lines or around the world,"
>he said, "but they export
> rhododendrons."
>
> The finding may have a major impact on how
>scientists manage the
> disease. Co-investigator David Rizzo, assistant
>professor of plant pathology
> at UC Davis, said it may result in new
>restrictions on the rhododendron
> nursery industry. "The big concern is that
>someone will transport a sick
> rhododendron to a place where there are
>susceptible oak species," he said.
>
> The breakthrough came when a Clive Brasier, a
>British researcher who had
> visited UC Berkeley last summer, later noticed
>in Europe a fungus that
> looked like one he'd seen in Garbelotto's lab.
>The European fungus had
> been found on rhododendrons in Germany and the
>Netherlands. Brasier
> contacted the UC scientists, and researchers
>from all four countries
> determined together that the European
>rhododendron fungus was identical
> to the California oak-killing agent. This
>finding established that the fungus
> is not exclusively found in California and has
>important implications for
> international trade.
>
> But Rizzo and Garbelotto needed more proof to
>confirm the link between
> the two plant species, and yesterday they got
>it. Rizzo and Steve
> Tjosvold, a Santa Cruz County farm advisor,
>found the fungus in a
> rhododendron taken from a Santa Cruz County
>nursery, and Garbelotto
> confirmed with DNA analysis that it was the
>same fungus killing the oaks.
>
> The scientists don't know whether the disease
>was transmitted from
> California to Europe, or vice versa, or whether
>it traveled to both places
> from a third, as yet unknown, location. The
>fungus, first noted in European
> rhododendrons in 1993, has not been found in
>European oaks. However,
> European scientists are concerned that the
>disease will spread to European
> oak forests, particularly those in areas with a
>climate similar to that of
> California.
>
> Since the discovery of the mysterious
>oak-killing illness in California in
> 1995, researchers have been scrambling to
>understand the disease and
> design strategies to stop its spread. It is not
>known if the fungus recently
> was introduced into California, or if it is a
>native fungus that recently
> became a tree-killer because of environmental
>changes. Tens of thousands
> of oak trees have succumbed to the disease, and
>the researchers have
> reported up to 80 percent mortality in some
>infected groves.
>
> Through molecular sleuthing, Rizzo and
>Garbelotto determined that the
> disease was caused by a never-before-seen
>strain of fungi from the genus
> Phytophthora (Phy-TOFF-thoruh). A relative
>belonging to this 60-member
> group caused the Irish potato famine, and
>another relative is linked to the
> dieback of cedar trees in Northern California
>and southern Oregon,
> eucalyptus trees in Australia and oaks in
>Mexico, Spain and Portugal.
>
> In California, Sudden Oak Death has been
>reported from Sonoma Valley in
> the north to Big Sur in the south, a 190-mile
>range, as well as east to the
> Napa County border, about 25 miles inland. The
>hardest hit counties are
> Marin and Santa Cruz. The disease affects
>tanoak (Lithocarpus
> densiflorus), coast live oak (Quercus
>agrifolia), and California black oak
> (Quercus kelloggii) found along the coastal
>belt in California. To date, the
> disease has not been found in other oaks such
>as blue oak or interior live
> oak.
>
> The dieback is alarming, researchers say, for
>its potential to disrupt the
> coastal forest ecosystems. Oaks provide habitat
>for wildlife and a food
> supply for small mammals and are frequently
>planted as ornamentals in
> gardens and parks. Additionally, downed dead
>trees create a fire hazard
> from the resulting buildup of dry fuel.
>
> There are similarities between the disease in
>oaks in California and
> rhododendron in Europe. In both cases, the
>fungus attacks above ground
> parts of the plants. In oaks, the fungus enters
>through the trunk and
> causes the formation of bleeding cankers on the
>trunk. On rhododendron
> plants, the fungus causes similar cankers and
>spreads from twig tips to the
> stem base, according to the European
>researchers.
>
> The researchers have notified agricultural and
>ecosystem managers in the
> affected areas of the rhododendron discovery.
>Research is underway to
> determine if native rhododendrons - those that
>have not been imported -
> are being infected. Research also is being
>conducted to determine how
> many other susceptible species may be affected
>by the fungus.
>***************************
>Dr. Andrew J. Storer
>Division of Insect Biology
>201 Wellman Hall
>University of California
>Berkeley, CA 94720-3112
>USA
>Tel: (510) 642 5806
>Fax: (510) 642 7428
>email storer@nature.berkeley.edu
>
>
>
