Fort Worth weekly gazette. [volume] (Fort Worth, Tex.) 1882-1891, 1890-08-07
What is Pear Blight?


What is Pear Blight?
This is q question often asked, and the
answers offered by persons protesting TO
know all 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 a species of bac-
terra. In other words, pear blight is
caused by minute fungus or plant,
which lives in the pear twigs and bark
as u true parasite and kills as result of
its presence. The common names
Hblight' and "rustr and "die 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 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 botanist, EMU
merated twentY-three species OF fungi
that are known to occur on the pear. Ot
these the greater number are true para
sites which live at the expense OF the
pear and are more or less Injurious to 1t.
OF these pear diseases caused by fungi,
only four have done sufficient damage to
attract particular attention.
1t is highly probable, saws Mr.. Wait,
that no disease of plants has been more
discussed and written about than pear
blight. Tie first positive record of the
occurrence of this disease is on the high
land of the Hudson in 1893. The first
American book on fruit culture, pub
lished in 1917, contains a chapter on
blight III the pear. Since that time there
has been no end of articles in horticultu-
rel papers, books and journals, especially
i'll 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 1t TO the work of
| insects, others to freezing and frozen
| sap. Some thought 1t was due to an
| over-supply OF sap, while others TO de-
| ticiency of the same. But 1t was re-
| served for Professor Burrill of the uui-
versity of Illinois 10 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 speculh-
| tious and theories concerning 1t, and
practically cancelled all that had been
written previously concerning the cause
of blight. The observations of the other
! writers US TO mode OF occurrence and
distribution still remain of value. In
| 1883 Professor Burrill published name
and description of his new species of
microbe. 1t is now known to botanists
rs Micrococcus amylouorus. From 1884
TO 1887 Professor Arthur of New
York experiment station, conducted q
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 q
result the proof that the microbes cause
the blight is Us 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 Asistic cholera, and cutting out the
affected branches may retard the maladJ
until the period has passed, in which
case the tree stands q chance for recov-
cry, otherwise the tree, even though bu
slightly affected, to ell appearances, il
doomed.
Unfortunately pear blight is already
! too familiar to most orchardists TO neet
! much by way of description. In general
the blight may be recognized as
, rather sudden dying back of the ends o
/ the branches without any evident cause
The leaves, shortly after the death o
I | tha hrenches die as natural result
; and the dead branches present the sam,
appearance as limbs that are accident
. ally broken of. The freshly killet
twigs present something of blackene(
> appearance, as if broken off from In
: tree, though the wood retains a degree
/ ! of moisture that would not characterize
r the severed twig.
[ The point of first inspection is almos
g invariably blossom spur. In the ear
e her stages of the disease only the fruit
0 ing SPURS and tips of the branches ar
= blighted, but as the disease runs on
o spreads downward, killing the large
= branches, or even the whole tree. j
n frequently runs around a large branc
+ from diseased spur, and girdles IL com
r pletely. All above this eventually dies
q although the leaves may remain gree
9 for some time. The disease progresse
b. on the main limbs only in the inne
II bark and cambium layer, this being tn
only vital part. 1t appears on the trun
d and main limbs as dead, slightly sunke
o patches. The work of the previous yea
II is told by the dead weather-bea
% branches. The tree at once forms lays
n of cork or bark over the healthy part
n thus healing up the wound. A remark
e able case is frequently ssen In which II