Gotta be that
“fuzzy science” that politicians complain about.
No, not the
government-funded stuff about crack babies, LSD-induced
mutations and how marijuana has no worthwhile medicinal
purposes. This is about scientific research that suggests a need
for precautions that would affect powerful economic interests
with friends in high places.
Back in 1993,
oak trees in California’s San Francisco Bay area started
dying. The phenomenon became noticeable in forests, mostly on
public land, but soon engulfed the dream houses of those with
the money to build up in the hills. “When trees start dying
next to houses worth three, four or five million dollars for a
two-bedroom home, it starts to affect the value,” noted Dr.
Matteo Garbelotto, a University of California - Berkeley plant
pathologist and the speaker at the August 19 science lecture at
the Smithsonian Tropical Research Institute’s Tupper
Auditorium.
The subject was
the search for knowledge about Sudden Oak Death, which
Garbelotto characterized as the worst contagious tree disease to
hit North America since the chestnut blight that ravaged the
eastern woodlands beginning with its introduction from Asia in
1904.
The epidemic was
germane to Garbelotto’s field of expertise, and his lab was
conveniently located near its epicenter, so it was logical that
his services would be called upon. However, he soon found that
the job was “not something you can do just being a plain
scientist.” Lots of public relations and politics would be
required for this task, and because this is, after all, taking
place in California, a sense of humor about the weird also
helps.
The case was
baffling because there wasn’t an easily detected cause for
the disease. Moreover, the way it spread and the way it killed
trees looked a lot more like the work of tropical fungi than any
know temperate forest blight. A number of journalists who felt a
need to sound more certain than they should have been picked up
on scientists’ comments about the similarities, and the
unknown disease vector was then frequently and, as it turned
out, erroneously, referred to in newspapers as a fungus.
It wasn’t
until 2000 that the cause of the infection was discovered. It
was not a fungus, nor, as was sometimes mistakenly reported, was
it an algae. It was Phytophtora ramorum, a protozoan related to
diatoms and kelp, “an organism unknown to science” at
the time of its discovery.
Now that the
cause was known, and as the final effects were what put
scientists onto the case in the first place, then the paths were
outlined for some massive and difficult scientific work. It is
not, you should understand, enough to identify a pathogen and to
know that it kills certain trees. If you want to control a
blight, you need to know how the pathogen spreads. If you want
to know how a pathogen that was previously unknown to science
spreads, you need to know basic things like how it reproduces,
and upon which sorts of substrates it can survive and thrive.
That’s even before you get to the point of looking for
something that kills or contains the infection, if such a thing
exists.
Once the
pathogen was identified as a member of a kingdom of water
plants, that was a clue that fit in with previously observed
facts, especially the tendency of trees to die in clusters, some
apparently along the paths by which surface or ground waters
flow. (It’s not so simple, however --- the blight does not
spread along rivers like some plant diseases do. Nor, for that
matter, does it follow roads like certain other blights.) In
that sense, Sudden Oak Death was like the Port Orford Cedar Root
Disease, a water and soil borne malady that’s wiping out a
west coast cedar species, or Oak Root Canker, a blight
that’s killing oaks in Southern Europe and Australia, which
is also water and soil borne.
It turned out
that P. ramorum, an organism that does not use photosynthesis,
does indeed put out spores that spread through water. But oddly
enough, the cankers on infected oaks are not found in the roots
as one might expect would be the case in a contagion spread by
soil and water. A tree that’s dying from Sudden Oak Death
starts to bleed from the bark, and the spread of lesions --- all
above the soil line --- within a few months girdles the tree in
much the same way as if somebody took a machete and stripped
away a ring of bark all the way around a tree. After that quick
girdling process, the tree slowly dies.
The first really
big discovery after P. ramorum’s identification was a
behavior that resembles many tropical phytopthora that both
girdle trees and affect their foliage and fruit. “The
infection comes from down up, and then showers spores
down,” Garbelotto explained. Researchers found the spores
in rainwater. Consider the implications of THAT.
“The life
cycle of these organisms is extremely complex,” the guest
speaker noted, going on to describe a study of the potato blight
that caused massive human tragedy and ultimately revolution in
Ireland, and which also seems to have a life cycle like hat of
P. ramorum.
If the spores of
P. ramorum are spread in the rainwater, that not only makes
containment a serious practical problem. It means that the
infection may be present in many more plants than just the oaks
that people see dying. And in fact, that’s the case. The
organism infects other trees that it does not kill, and from
them emits spores that then attack oaks. It seems that P.
ramorum is especially contagious among bay laurel trees, where
its infection is shown by brown spots, yellow halos and dead
tips on the leaves.
It also turns
out that P. ramorum infects redwoods, causing needle loss but so
far as is currently known, not endangering the lives of the
trees. However, when it became known that these icons of the
Californian identity were susceptible to infection, that became
the basis for more than one sensationalist news report.
Buckeyes,
maples, douglas firs and various understory shrubs also catch
the infection, and as if just to make things difficult for plant
pathologists, tend to cause very different symptoms with each
species.
The infection
thus spreads through whole forests, with the cutting or burning
of infected plants offering no real solution. Garbelotto noted a
tendency for douglas firs to move into areas where the oaks have
been killed by P. ramorum, but that the new firs, too, are also
affected by blight.
The main line of
research now switched to the DNA lab. For many reasons, the
ancestry of the various samples that were being collected in the
field became important.
(Actually, the
DNA analysts were busy all along. One of the reasons why so much
of the battle against Sudden Oak Death has taken place at
Berkeley is that they have a large, well funded biology lab with
a large and highly qualified staff, several of whose members
acquired part of their expertise in Panama by working with the
Smithsonian Tropical Research Institute. Like few other
institutions, Berkeley has the resources to pursue a blight
which at the outset posed an obvious menace to real estate
values and the tourism and outdoor recreation industries.)
The problem was
that it’s very difficult to isolate the DNA of this
organism by the usual means of growing it in a culture. Various
alternatives to culturing were tried, but what seemed to be the
most sensitive and useful was the PCR survey, a technique like
that used to discover whether a few grains of genetically
engineered corn have been mixed into a container load of the
natural stuff.
Now political
pressures kicked in. The PCR technique hadn’t been
previously used in this sort of plant pathogen study. If the
Berkeley researchers found what was appearing increasingly
likely, that the P. ramorum infection is widespread throughout
large parts of California, that would have serious consequences
for a couple of industries. The state’s nurseries export a
lot of trees and potted plants to points all over the United
States, and to a lesser extent so does its organic soil
composting business. You might guess what other states might do
with regard to plants and soils coming from a state that makes
you throw away fruits coming from other places as you cross its
borders, so as to protect its agriculture from introduced plant
diseases.
Thus Garbelotto
was reminded that he’s just a lowly plant pathologist and
the government insisted on DNA evidence gleaned through
culturing rather than PCR assays before making any decisions
based upon the Berkeley research.
(It’s that
“fuzzy science” bugaboo again, folks --- ludicrous
“research” that supports the War on Drugs may be the
sort of stuff that Uncle Sam wants to buy, and if you can use
novel techniques to develop a weapon that kills Muslims but
leaves oil wells intact he may have money for that, too, but
don’t go talking this gibberish about global warming
because the energy industry that brought you the California
electric crisis and the current administration in Washington
doesn’t want to hear about it. And don’t go to
Sacramento spouting off any fuzzy scientific facts or theories
that might devastate the California nursery industry.)
But in the field
and back at the lab, the research continued while the
politicians and lobbyists dithered and denied.
Red oaks and
tanoaks are definitely being killed off by P. ramorum. “It
doesn’t seem to be on the white oaks yet,” Garbelotto
said, but added that in the lab researchers have been able to
induce an infection of that tree species. So far, 18 host
species have been identified to the satisfaction of the
California government, but a bunch of other plant species seem
to also be affected and the research to confirm the suspicions
is underway. What California, and now parts of Oregon, confronts
is “a broad-host infective species.”
The
investigation got more minute. Different mechanisms by which
oaks and tanoaks are infective were noted. It was found that
juveniles of oak species are not affected, but tanoaks of all
ages are. Mortality in diseased tanoaks was found to be very
high, but it’s less than 50 percent in infected oaks.
Studies were undertaken to discover precisely how contagious the
P. ramorum spores are among oaks. It was discovered that spores
showered down from oaks won’t infect bay laurels or
rhododendrons, but infected soil will spread the disease to
these plants. The myriad styles of sporulation in different
plant hosts proved to be “a big headache” for
scientists.
The
investigation branched from pathology into ecology. It was noted
that ants will move soil up trees, infecting and ultimately
killing the trees in that way.
(As the
importance of soil infection became better known, the hydra of
politics, business and law raised its many heads again. It turns
out that US federal regulations can be very strict about traffic
in infected plant materials that may affect interstate commerce.
Other rules of the sort that began after the boll weevil hitched
a ride from Central America to the USA in the late 19th century
and proceeded to do a number on the American cotton industry
attempt to suppress the spread of insect pests. However, there
is nothing at all on the books that contemplates soil-based
pathogens. Will that change in light of Sudden Oak Death?
That’s a lobbying rumble to come, with huge economic stakes
for all concerned.)
Ecological
research also pointed to the hydrology of the P. ramorum
infection. It turns out that in inland areas, the peak time for
the protozoa’s spread is during the rainy season. This
seasonality is not so marked on the coast, where it rains a lot
more throughout the year. Looking a bay laurel leaves,
scientists found that where the morning dew accumulates is the
same place where the infection takes hold. Thus, Garbelotto
opined, “you have to have free-standing water for a long
time --- maybe 12 hours --- to get significant infection.”
On the other hand, he speculated that a lot of rain may wash the
spores off of the leaves and thus limit infection. More research
is underway along those lines.
Back in the DNA
lab, the hunt has been on to find out where P. ramorum comes
from.
In Europe,
there’s P. lateralis, a species of protozoa that’s
related to P. ramorum, which unlike its California cousin
reproduces both sexually and asexually. P. lateralis is an
obnoxious pathogen like P. ramorum, so its importation into the
United States, even for laboratory studies, is strictly
prohibited. However, in these days of Internet communications
the inability to do side-by-side studies in one lab is a slight
annoyance rather than an insurmountable research obstacle, and
preliminary DNA comparisons have been made. Based on those,
Garbelotto believes that P. ramorum was introduced into the
United States from Europe (note the political warning flags
aloft!) but that “these two populations have not seen one
another for a long time.” Whether those beliefs can be
confirmed or ruled out may take longer than the Berkeley
researchers would like, because there aren’t as many data
available from Europe as they’d like. (On the other hand,
this problem provides a perfect excuse for some of them who may
relish the prospect to spend some time living and working in
Europe.)
So is the
scientific work started in response to Sudden Oak Death now
narrowing down to just a few specialized lines of inquiry?
Not a chance.
“Once you
have opened a can of worms, it’s open,” Garbelotto
said. “Now we have three species” of phytophtora out
and about on the US west coast. The other two are not as a
aggressive as the one that causes Sudden Oak Death and may be
native to California.
Moreover, there
are the not-so-small matters of cure, prevention or damage
mitigation. At the moment there are inoculation experiments
underway to study the resistance of various species to infection
and, once infected, to damage caused by infection. “This
pathogen is never going to go away,” Garbelotto opined,
posing the replacement of dead trees by more resistant ones as
one of the primary responses to the blight.
There is also
research into chemical and biological controls. It seems that
certain chemical injections are of some use in preventing
infections to some trees, and other substances are being tried.
The hunt is also on for natural resistance to P. ramorum, and to
the extent that certain biochemical molecules or genetic
sequences may be discovered in that search, other initiatives in
basic and applied science may become timely.
Politics and
plain old weirdness have made themselves felt in the search for
controls. Garbelotto’s lab has been inundated with
suggestions ranging from sprinkling trees with holy water to
strange incantations that would cast P. ramorum into a parallel
universe where they’d be someone else’s problem. Some
of the more bizarrely unscientific suggestions have come from
people with political clout. To humor the California public, the
hard-working scientists and himself, many of these suggestions
have been tested. No, holy water doesn’t work. Nor does
anointment with holy oil. But there comes a point when
researchers with work to do and intelligences capable of being
insulted draw a line, and in one of those Berkeley revolts such
a boundary was inscribed this side of the parallel universe and
people at the lab refused to do a study of that particular
hypothesis.
Meanwhile, much
more serious decisions loom. The Berkeley lab has been testing
plants from commercial nursery stocks, and not only have they
found P. ramorum infections, they have found both sexes of the
species in these samples. A blight-causing organism that appears
to have spread only clonally might now be prepared to reproduce
sexually and that could carry with it many consequences, not all
of which can be foreseen.
Thus, state and
federal authorities may want to control the nursery plant
business and the movements of compost and other soils. Big
industries and people’s livelihoods are at stake. Political
controversy is inevitable. “There’s a huge amount of
pressure,” the plant pathologist concluded.
Also in this
section:
Investigating Sudden Oak
Death
West Nile virus
spreading
