Some musings on current local tree diseases

I don't know if this newest possibly affected species
made the international news as well, but researchers
in California are worried.  They've found the same
Sudden Live Oak Death fungus growing at basal shoots
of the mature Coast Redwood trees, and are still
unsure if it will damage them or they just serve as a
host species.  Amongst the trees being examined, are
several on the nearby University of Calif Berkeley
campus.

In my neighborhood, I haven't seen many signs of 
Coast Live Oaks, coast Redwoods, Tanbark Oaks or Black
Oaks being harmed, and in my yard have several
susceptible species with no dieback.  The fungus seems
to prefer trees growing in wild areas with more
coastal influence, rain and regular low fog, typically
closer to the sea or bay. So far, most trees in
gardens are not being impacted.  One wonders if this
is a natural phenomenon or linked with air pollution
and accumulations of heavy metals and soil pH change. 
Could it be the first indication of acid rain effects
along the coast as well as  the Sierra Nevada
mountains and higher peaks surrounding the Los Angeles
basin?  These higher peaks have for some time been
becoming more acidic, with spikes in tree losses
amongst species such as Ponderosa Pines, reduction of
higher altitude amphibian populations, etc.

The article sounded alarmist, as if the entire
population of trees around the state were at risk.   
There hasn't been much ongoing discussion of spread
and mortality reports of different species, except to
continue citing worst case examples such as China Camp
State Park, right along San Pablo Bay. They have
closed  campgrounds there to allow removal of entire
groves of dead Quercus agrifolia endangering
campsites.  Nearby San Rafael and Sausalito have just
as many Live Oaks, with few reports of similar die off
so far.  

The insect and fungal attacks on Monterey Pines in
Monterey and San Mateo Counties to the south of San
Francisco is an ongoing problem as well, but hasn't
gotten much continued local press coverage.  It is
possible to see signs of the first symptoms, dead
branch tips in many urban plantings, such as along
Highway 280 around Daly city, leaving San Francisco. 
The worst affected trees seem to be located where it
is the most foggy and windy, ordinarily considered to
be their ideal habitat.    

The slower growing Giant Sequoia/Sequoia giganteum is
generally more susceptible to disfiguring fungus
attacks at branch tips in lower elevation coastal
urban plantings, but usually it doesn't kill the tree.
 Coastal Redwoods can also suffer twig dieback, but
more often when trees are under environmental stress. 
In most of northern California, S. sempervirens simply
thrives with good soil and sufficient water.  It can
suffer in smoggy parts of Los Angeles, and rarely ever
looks as good as it does in northern California.  The
coast Redwood also does surprisingly well in dry hot
summer locations with cool/cold winters, such as The
Napa Valley and Sacramento Valley.  They do need
supplemental irrigation or tapping into a water table
to survive on just rainfall in these inland locations.

For those in other European mediterranean climate
areas, Coast Redwoods that I've seen at their best
were all located in generally mild, cool winter areas
with regular rains or summer fog.  They grow so well
in the Italian Lake District, that Lago Como reminded
me of Tiburon/Sausalito/Mill Valley in Marin County. 
Coast Redwoods also were beautifully adapted in the
hills of Sintra, Portugal, with its regular wet fogs
in summer, keeping the ground plenty wet.

I wonder if the Phytophora fungus involved is as
active in other parts of the world besides California,
western Australia and England?  It is interesting that
all three locations are coastal and exposed to
prevailing westerlies over vast oceans. 

  


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