Fort Worth daily gazette. (Fort Worth, Tex.) 1882-1891, 1890-08-03

What is Pear Blight?
This is a question often asked, and the
answers offered by persons protesting TO
know IL about such things do not har-
monte in every case so far as relates to
the cause of the trouble Perhaps the
best authority on pear blight that we
have is Mr.. b. NJ. Wait of the United
States department of agriculture. He
says it is a specific disease peculiar to
the pear tree and due TO n species of bac-
terra. In other words, pear blight is
caused by a minute fungus or plant,
which lives in the pear twigs and bark
as true parasite and kills as result of
its presence. The common names
"blight' and "rust'' and Idle back'
are often used rather vaguely to name
any OF the diseases or injuries to Vegeta-
ton. But in this case we are dealing
with q specific disease which is peculiar
to the pear and its allies. This is by no
means the only disease of the pear tree.
Won Thumen, German botauist, EMU
merated twentY-three species of fungi
that are known to occur on the pear. OF
these the greater number are true para
sites which live at the expense of the
pear and are more or less injurious to it.
OF these pear diseases caused by fungi,
only four have done sufficient damage to
attract particular attention.
IT is highly probable, says Mr.. Wait,
that no disease of plants has been more
discussed and written about than pear
blight. The first positive record of the
occurrence of this disease is on the high
land of the Hudson in 1898. The first
American book on fruit culture, pub
lished in 1917, contains a chapter on
blight IN the pear. Since that time there
has been no end of articles in horticultu-
raj papers, books and journals, especially
in recent years. All sorts of theories
and speculations have been INDUCED In
by horticulturists and fruit growers con-
corning the cause of the disease. The
theories are usually as different as the
individuals in whose brains they orig
mated. Some attribute it to the work of
insects, others to freezing and frozen
sap. Some thought it was due to an
over-supply of sap, while others to a de-
ficiency of the same. But it was re-
served for Professor BurrilI of the uni
versity of Illinois to discover the real
cause of blight. This he did in 1880.
Professor Burrill's remarkable discovery
of the bacterial nature of this disease
forever put an end to the wild specula-
practically cancelled all that had been
written previously concerning the cause
of blight The observations of the other
writers as to mode OF occurrence and
distribution still remain of value IN
1883 Professor Burrill published q name
and description of his. new species of
microbe. 1t is now known to botanists
as MicrOcoccus amylOuorus. From 1884
to 1887 Professor Arthur of New
York experiment station, conducted a
very careful series of experiments in the
study of pear blight. He fully corrobo-
rated Professor Burrill's work, and dis
covered valuable new facts about the
disease. Professor Arthur carried out
his experiments with more completeness
than had been done before, and as
result the proof that the microbes cause
the blight is as perfect as any biological
demonstration can ever be. Still, in the
light Of all these discoveries, the only
remedy known is to cut out the diseased
parts, and even this can never be re-
garded as an entirely effectual remedy.
Blight seems to run in periods little
like Asistio cholera, and cutting out the
affected branches may retard the malady
until the period has passed, in which
case the tree stands a chance for recov-
cry, otherwise the tree, even though but
slightly affected, TO all appearances, is
doomed.
Unfortunately pear blight is already
too familiar TO most orchardists TO need
much by way of description. In general
the blight may be recognized as |
rather sudden dying back of the ends of |
the branches without any evident cause.
The leaves, shortly after the death of |
the branches, die as natural result, |
and the dead branches present the same |
appearance as limbs that are accident |
ally broken off. The freshly killed |
twigs present something of blackened |
appearance, as if broken off from the |
tree, though the wood retains a degree |
of moisture that would not characterize |
the severed twig.
The point Of first inspection is almost |
invariably blossom spur. In the ear
her stages of the disease only the fruit
ing SPURS and tips of the branches are
blighted, but Us the disease runs on il
spreads downward, killing the larger
branches, or even the whole tree. 1t
frequently runs around large branch
from diseased spur, and Rirdles it COM
pletely. All above this eventually dies,
although the leaves may remain green
for some time. The disease progresses
on the main limbs only in the inner
bark and cambium layer, this being the
only vital part. 1t appears on the trunk
and main limbs as dead, slightly sunken
patches. The work of the previous year
is told by the dead weather-beate |
branches. The tree at once forms a layer
of cork or bark over the healthy part,
thus healing up the wound. remark
able case is frequently seen in which the