The Trail Companion
Oak Mortality Syndrome
So far the disease has
only been seen in wildlands, not in street trees or
in yards [where it appears near homes it has always
been in trees that are functionally part of adjacent
open space]. There are other diseases that also
occasionally kill trees, particularly those that have
been stressed through injury, compacted soils,
overwatering, air pollution, etc, but the causitive
organism for the oak mortality syndrome has not been
identified as occurring except in wildlands so far.
Wildlands with much human use, like China Camp State
Park on the shore of the Bay in Marin County, does
seem to be a possible correlation, however.
It is difficult to
make any recommendations yet. The main ones are:
don't move infected wood to new areas, and don't move
mud from the vicinity of infected trees to new areas.
Dead wood should be allowed to dry out.
It has been shown that
the disease comes first, then the insects, so
insecticides are not considered promising for
New understandings are
expected to be coming along in the coming weeks and
months, since we now have a much better idea what we
are dealing with and it is being studied intensively
by many people.
Some arborists present
at the meeting said they are seeing a marked increase
also in wetwood infections -- another disease, caused
by bacteria. Part of the problem is that we have so
many very old oaks, not so many middle-aged or young
ones. Old oaks seem to be more vulnerable to
I thought it was a
great idea to bring in an expert on the pine pitch
canker disease containment problem, Richard Hawley of
Greenspace The Cambria Land Trust, though it is
caused by a totally different organism in different
ways, the lessons learned are worthwhile. He brought
a great publication "Programs for Capturing,
Handling, Utilizing, and Disposing of Infected Pine
Material in San Luis Obispo County". One little
tidbit I picked up from his discussion is the problem
of pallets. Packing materials are typically built
crudely of unfinished wood, and sometimes still have
the bark on them -- and thus are a probable vector
for spreading disease from continent to continent,
sort of the botanical equivalent of ballast water,
which has brought so many foreign organisms to San
Francisco Bay that an estimated 80%+ of the biomass
of the Bay consists of introduced organisms.
All three panelists
gave us some historical perspective on other tree
declines, of which there have been many in the last
100 years, most notably the loss of the American
Chestnut, which began in 1904 and was complete by the
1950s. The first slide was a very old photograph of
American Chestnuts -- so big their trunks looked like
old growth redwoods -- the trees grew to 10' in
diameter and over 100' tall, and over about 45 years
all were at least top-killed in their extensive
native range, where they were once a dominant tree,
with huge ecological effects. In North America in
this century there have been significant declines of
oaks, maples, birches, ashes, sweetgums, beeches ...
also in trouble in recent decades the Monterey pines,
some Colorado pines, aspens and dogwoods. Western
Australia suffered a particularly serious decline of
Eucalyptus, involving many species with very high
mortality, turning some forested areas into
Jeffrey A. Caldwell
Garden Habitat Network
Jeffrey A. Caldwell, along with
Andreas Reimann are preparing an initiative to
establish a garden habitat network to preserve and
restore biodiversity in our inhabited landscape - the
California Garden Habitat network. If interested,
contact Andreas at
email@example.com or 530-754-9478.
This letter originally appeared in the California
Natives mailing list and is reprinted by permission.
To subscribe or for more information, see the California Native Plants Discussion
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