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Center - General
Bioinvasion:
A Great Threat
By
Jerry Pulley
Tree Clinic Quarterly, Fall 2002
About
240 million years ago, the Earth's landmasses combined into a
single continent. That immense plaque of rock we refer to as Pangea
sat amidst an even more immense global ocean. With steady geologic
pace the rockmass fragmented and sailed throughout those immense
waters to create our present continental map.
From the perspective
of the human moment it seems the structure of our planet is surely
one aspect of the world that humans cannot change. Evidence however
suggests otherwise.
With ever increasing speed the world's economy is pushing its
many ecosystems into each other. The currents of human movement
are altering the ancient evolutionary function of the global surface.
Historically,
the structural variety and the uneven surface of the earth have
held living communities in place. The barriers surrounding an
ecosystem set the terms of life within it. They tied a group of
plants and animals together and tended to exclude predators, competitors
and diseases that evolved elsewhere. Perhaps the most well known
example is the island of Galapagos where creatures like the giant
tortoise evolved into forms known nowhere else on earth. Today,
the heretofore physical barriers are losing their ecological reality
as more and more organisms are moved around them.
Until recently
the arrival of new organisms, or "exotic species", was
a rare event. Now it happens any time an airplane lands or a ship
ports. Exotics are arriving thousands of times faster than the
previous natural rate. These non-native species, when introduced
to a new area, can out-compete native species, cause disease to,
and ultimately wipe out native species. In any single ecosystem,
loss of species represents decline.
Under natural conditions the planet's physical structure (oceans,
deserts, mountain ranges, etc) imposes formidable barriers to
cross. Now those crossings are routine. Every few months we hear
of a "new" pest. One example is the Asian Longhorned
Beetle that arrived in shipping
crates at major U.S. ports only a few years ago. It is killing
thousands of maple trees in the New York and Chicago areas. It
has been found in Houston. The Emerald Ash Borer, a native to
Asia also arriving via shipping crates was discovered in Detroit
earlier this summer after the recent large-scale rapid decline
and death of ash trees. Citrus Longhorned Beetle, a relative of
the Asian Longhorned Beetle was recently found in a nursery in
the Pacific Northwest. It reproduces in the vegetation along river
systems and has the opportunity to impact thousands of trees,
miles of wetlands, wildlife, salmon habitat, fruit orchards and
ancillary services througout the Northwest. It has no known natural
predator in the United States to keep it's population numbers
in check.
Invasive plants
with no natural controls are troublesome throughout the world
from Hydrilla in our own Lake Austin to Kudzu in the southern
U.S. Water Hyacinth in Africa's Lake Victoria comes from South
America. Melaleuca, an Australian native, is choking out native
species in the Florida Everglades.
The list of
invasive exotic species seems endless. Exotic agents of disease
are more numerous than insect pests. Dutch Elm Disease, Chestnut
Blight, Oak Wilt, Sudden Oak Death (see page 4), Hoof and Mouth
Disease- all are caused by non-native invasive organisms.
The effective
collapse of the world's ecological barriers is a phenomenon without
precedent in the entire history of life, certainly human life.
Bioinvasion, the spread of exotics, is fast becoming one of, or,
perhaps the greatest threat to the Earth's biological diversity.
It seems to me that we are experiencing evolution in reverse.
TOP
Ancient
Trees- Our Link with the Past
By Jerry Pulley
Tree Clinic Quarterly, July 2002
I’m
a history buff of sorts-especially Texas history. My mom’s
maternal antecedents were veterans of the battle of San Jacinto,
the decisive event in Texas independence from Mexico in 1836.
I try not to bore folks with tedium but for anyone interested
I am happy to give you a story.
Last March
I took a friend on a historical tour. First, we drove to old Fort
Clark Springs, west of San Antonio. Fort Clark, established in
1852, is the best preserved of all of the Texas frontier forts.
In 1852, it marked the western edge of civilization. Beyond was
the Comanceria- Indian territory so well immortalized in the novels
of Larry McMurtry, Elmer Kelton and other Texas writers. The fort
was commissioned to protect the settlers from marauding Indians:
Mescalero, Lipan, Kiowa, and the war-painted horsemen of the plains,
the fierce Comanche.
The fort’s
original buildings, largely unchanged, surround the huge parade
grounds. The enlisted mens’ quarters, officers’ mess,
and the livery stables are all there. It’s easy to imagine
Buffalo soldiers of the 9th and 10th cavalry milling about.
The fort is
located just up the hill from the headwaters of Las Moras Springs
(the Mulberries). Originally the springs consisted of a strip
1-2 miles wide and extended downstream for several miles. In approaching
the source of the spring, we drove through a modern park with
an asphalt drive, grass neatly mowed, picnic and litter barrels
nicely painted and signs admonishing us not to litter. We found
the source- spring water bubbling up from the ground and contained
by a concrete wall looking something like the Army Corps of Engineers
might have dreamed up. Down stream a couple hundred yards was
a dam creating a concrete pond, or swimming pool.
My friend
commented, “What a shame. What do you think this originally
looked like?”
“It’s
not all gone” I replied, “The trees are still here.”
Grand, majestic
live oaks stand just as they did under Spanish rule, 300 years
ago. These were mature trees when the Alamo fell. They have grown
very little if any, in the 166 years since. All exist in a deteriorating
condition resulting from old age exacerbated by abuse and neglect
from their human keepers. Still, they are the living witnesses
to antiquity and they are there for us to appreciate. (continued
on next page) Few if any of these old soldiers will be there for
my grandchildren to see. The following generations will have to
be content with plaques and historical markers to describe the
first 200 years of Texas history.
Old trees
like old people are our living connection with the past. Go see
them both, and discover something about yourself; discover something
about our history. It’s better than reading about it.
Remember though-
time is short.
TOP
Letter from the President: Old Arboriculture
By Jerry Pulley
Tree Clinic Quarterly,1st Qtr. 2002
Last month
I said, "OK, it's time to formalize a mission statement for
Tree Clinic." As with many groups, we individually have a
notion of our mission, but we had not distilled the concept to
a declarative statement. We agreed that our mission is:
To serve clients
by solving plant health problems through the application of scientific
principles and procedures.
A few days
later, I was introduced to a fellow who, upon hearing my name,
said, "Oh, you're the tree surgeon!" He meant no insult-
it stung nonetheless. I replied, "No, I'm an arborist- a
tree biologist, actually."
My new acquaintance
who used the term tree surgeon was thinking what is called OLD
ARBORICULTURE. It was based on three elements: Cut the branches
close to the stem, paint the wound, and fill the cavity with concrete.
Old arboriculture is still practiced today to some extent. Why?
Ignorance, of course. People want to dress wounds, cut out decay
down to clear wood, and fill holes to prevent rot. In effect,
they want to… "treat trees like they treat animals"
(Shigo, Alex. Modern Arboriculture, 1991, pg.18). Trying to change
public perceptions of these treatments has not been easy, even
with all of the scientific evidence showing that many of the old
treatments do more harm than good. Old perceptions are indeed
very old:
"At the
beginning of recorded history, the Greek and Hebrew writings reference
crop maladies like rusts, mildews and smuts that were assumed
to result from the wrath of gods.
The philosophers Pliny and Theophrastus observed, and speculated
on the nature of diseases. It is interesting to note that Theophrastus
(300 BC) recognized that wild trees were not liable to the ravages
of disease, as were those that were cultivated.
Linnaeus, the
botanist responsible for our binomial system of scientific classification
published Species Plantarum in 1753. His contemporaries attempted
to classify diseases simply for the sake of classification. During
that time occult influences that presumed diseases to be the wrath
of angry gods still persisted although there was some awareness
of the role of the environment. It was during this period the
first pruning wound dressing was developed for fruit trees. This
appears to be the origin of the idea that wound dressings do something
for trees. This occult- fostered idea persists to this day. It
was not until another hundred years had passed that the chemist
Anton deBary demonstrated the causal nature of fungi in cereal
diseases and later identified the fungal causes of potato blight
that decimated the Irish population in the great potato famine.
In the evolution of plant science we see a series of transitions
from philosophical and occult interpretation to descriptive arid
taxonomic classification to the application of scientific investigation."
There is a wealth of information on diagnoses and management of
plant maladies available today to those interested.
We at Tree
Clinic will strive to solve your plant health problems through
the application of scientific principles and procedures.
TOP
Letter
from the President: Professional Accuracy
By Jerry Pulley
Tree Clinic Quarterly, 4th Qtr. 2001
The media
are preoccupied with terrorism, with good reason, of course; it's
certainly an urgent issue. Often though, in the reporting of urgent
issues, information becomes distorted. Pertinent information may
be poorly explained or omitted entirely. Distilled information
easily becomes misinformation. With something as threatening as
the concept of terrorism, or more specifically, biological terrorism
in the form of anthrax, misinformation promotes fear.
The other
day, in a radio report, I heard an officer of the CDC (Center
for Disease Control) refer to anthrax as a virus. Perhaps he simply
misspoke, and promptly corrected himself. If so, the correction
was not reported. That error constituted misinformation, because
it is important to know that anthrax is a bacterium (Bacillus
anthracis), not a virus. Bacterial infections are treatable with
antibiotics, viral infections are not.
Scientists
and reporters alike must be careful to speak accurately. As an
arborist and diagnostician, I must be careful not to advocate
for a tree or its disease. If I can relate the facts in full,
my client can make an informed rational decision about a course
of action to take.
One common
tree disease I see every spring and fall is requiring greater
detail in explanation these days due to its name. The tree disease
anthracnose is caused by a fungus. Fungi are entirely different
from viruses or bacteria. The name, which sounds very similar
to the bacteria disease anthrax, may cause alarm to clients in
these troubled days. Even though the names are similar, they are
not similar diseases. The word root anthrac- is derived from the
Greek word meaning coal, or charcoal (the lesion caused by the
cutaneous form of anthrax is black, or charcoal in appearance).
Add the prefix anthrac- to a suffix -nose, which means condition
or disease, and you have the word anthracnose, meaning "black
disease", which describes a plant disease caused by a fungus
and recognized by black, dot sized fruiting bodies on dead lesions
in the leaf. This disease is not lethal, and is treatable with
fungicides.
In the words
of Jacob Bronowski, "Man masters nature not by force but
by understanding". One way that fear and panic can be avoided
is for all of us who speak to the public to take care to speak
accurately.
TOP
Letter from the President: Spring Observations
By Jerry Pulley
Tree Clinic Quarterly, 2nd Qtr, 2001
Spring is
here, and the phone is buzzing. Lately I've been spending many
a weekday afternoon on the phone with clients who have concerns
about their trees. Reflecting on the many calls of late, it seems
to me that spring is the season when people observe the most detail
about trees. As the year progresses, detail in observations evidently
fades. A late season housecall in August may reveal a major limb
broken or even an entire tree that has turned brown. The homeowner
is often surprised, and will remark; "I hadn't noticed that!"
Spring is
different. After several months of cold and rain, we are anxious
to be out of doors, into the sun, and are delighted with signs
of new growth and new life. It seems that even the slightest detail
of seasonal development is observed. This usually helps when you
and I are trying to get to the bottom of a sick tree problem on
the telephone. For example, when you describe the detail of how
a developing leaf appears eaten away, it is easy for me to explain
the life cycle of the Snoran Tent Caterpillar, and the effect
on your tree.
We humans
suffer runny noses, colds, and flu during winter months. Trees
also suffer ubiquitous diseases, but show symptoms in spring,
when the environment is conducive to growth and reproduction.
Signs and symptoms of insect damage, foliar fungal infections
and nutritional deficiencies seem to show up overnight. Most are
not life threatening if addressed on a timely basis, but as with
human illness, they must be addressed to maintain optimal health
of the whole organism.
Unfortunately,
some tree diseases are life threatening. Oak Wilt is unquestionably
the worst that we deal with. This complicated disease is difficult
to discuss in a concrete matter-of-fact way. It can be discussed
only in the abstract. Almost any statement one can make about
the disease has exceptions, sometimes apparent contradictions.
Despite the best attempts at treatment, we often lose trees to
Oak Wilt. There are no guarantees, just as in treating some diseases
of man. Step one, for me, in helping a client address oak wilt
is to initiate a conversation that educates about what is known
and perhaps more importantly, what we don't know about this devastating
tree disease.
So, go outside-
take a look around. Observe your trees, and if you see anything
that concerns you, give me a call.
TOP
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