On April 7, the Garber Park Stewards were pleased to host a Citizen Science Workshop focused on Sudden Oak
Death, presented and led by Lech Naumovich, Ecologist, of the Golden Hour Restoration Institute.
Well-attended by naturalists,
arborists, landscapers, trail workers, and interested citizens, the workshop
provided in depth instruction and commentary on the current state of research
and understanding about the disease. Click here for a PDF of Lech’s excellent 4 page handout on SOD resources. In some ways more compelling than an update
on the research, this workshop provided hands on and eye witness evidence of
the existence and the material indicia of SOD infection in the oak forest of
Garber Park.
It is one thing to look at
photographs of the pathogen and its effects on living forests, but it is quite
another to recognize the characteristic bleed of an infected tree right in
front of you. Perhaps
counterintuitively, the pathogen slowly and methodically kills an oak tree by
girdling the main stem. Looking directly
at this process, you cannot avoid an increasing appreciation of the complexity
of the SOD blight in the landscape that surrounds you. Even the ground breaking
research of Matteo Garbelotto’s UC Sudden Oak Death Lab does not suggest a
strategy for “saving” a forest under attack.
The pathogen itself is a
recent (within the last 20 years) stowaway on nursery stock (probably rhododendrons)
and within its own biological limits has spread rapidly into Northern
California backyards and forests which are evolutionarily unprepared to fend it
off. The bleed on an infected oak is
evidence of resistance in the victim, but the functions of immunity are poorly
understood to date. The highly vulnerable tan oak forests of Marin County
exhibit a mortality rate over 90% while the Coast Live Oaks exhibit only 55%
mortality—perhaps due to innate or developing immunity. Currently available chemical treatments aim
to boost the immune response of particular trees in order to save them. But a
forest is a great deal more than a de facto gathering of particular trees.
In the complex riparian
woodland of Garber Park, each of the four constituent trees (and many shrubs)
is affected by the pathogen. The Big
Leaf Maple and the California Buckeye are passive carriers. The pathogen aggressively feeds on the leaves
of the Bay Laurels without killing the tree and the Bay Laurels serve as a vector for the
conveyance of the pathogen through the forest.
The Coast Live Oak appears to
be an unintended victim and a dead end for the pathogen. An infected oak has not been shown to
transmit the pathogen to another host. Yet, the possible consequence of 55%
mortality of Garber’s Coast Live Oaks is a circumstance of great magnitude from
every point of view including the loss of mature canopy and fire hazard that
would exist from numerous downed heritage oaks.
As the Workshop demonstrated,
there are no solutions or prescriptions at this time for “saving” an infected
forest, though there may be ways to “save” an infected tree. Deepening research and increasing experience
of arborists may hasten the time when there are proven strategies. But there are many things we can do now as
interested individuals and groups. We
can support the work of the SOD Lab by participating in the upcoming SOD Blitz
at the end of April. The Garber Park
Stewards are using the SOD Blitz to better assess the rate and range of infection exhibited by Bay Laurels. Using a grid system we will collect apparently symptomatic leaves and submit them for testing. The results will be available in October.
Sign up now to help with the SOD Blitz 2012 on the
weekend of April 28-29 Attend a one-hour long training offered by U.C. Berkeley
Dr. Matteo Garbelotto, and then collect symptomatic bay leaves. Return samples to a drop box at the training
site by Sunday evening. To sign up for the UC Berkeley training, go to http://sodblitz2012.eventzilla.net. To help in Garber Park contact garberparkstewards@gmail.com
We can hone our
understanding by recognizing the pathogen and closely observing its operations
in Garber Park’s forest. Phytopthera ramorum is an invader which
may become endemic. Whether by direct intervention or more passive
strategies, it behooves us to do as much
as we can to spare our native landscape the worst effects of this pathogen.
