East Oregonian : E.O. (Pendleton, OR) 1888-current, 1910-07-05

Fire Blight is the most serious of
all the diseases which attack the pear
and apple. 1t is a contagious disease
Of bacterial origin which, under prop
er conditions. may attack any part
OF the tree, besides the pear and ap-
pie. the ounce, wild crab-apple, haw-
thorns mountain ash, serviceberry
and some other pomaceous trees are
subject to attacks Of this disease
Cause of the Disease
Fire Blight is caused by minute
organism belonging to the group Of
bacteria and known technically as
Bacillus amylovorus It Is rod
shaped, motile germ which divides
very rapidly by simple fission and
is found in immense numbers in the
diseased tissue. The germs are so
minute that they measure only about
1-25,000 of an inch in length and are
visible only under the highest magni-
fication OF the compound microscope.
Proofs of the Bacterial Nature of the
Disease.
Myriads of germs are present in all
freshly blighted portions of the tree
and in the stick ooze from exuding
cankers Pure cultures of the or
ganism may be obtained from diseas-
ed tissue and cultivated for genera
tion after generation on suitable cul-
ture medic. Healthy tissue inoculated
with germs from a pure culture will
become characteristically diseased.
The germs are found in abundance in
the tissues so inoculated and when
grown in pure culture and compared
with germs from naturally infected
tissue, and with those used to pro-
duce theTartificial Infection, are found
TO be identical.
Part of the Tree Affected.
The germ lives almost entirely in
the sappy portion of the bark. though
in some vigorous-growing varieties of
pears the germs have been known to
invade the sap wood to a limited ex-
tent. When inoculated into the grow
ing tips OF branches, into the blossom
or the fruit. the germs are found gen.
orally throughout the tissues.
Distribution.
Fire Blight occurs in more or less
severity in nearly all parts OF tie
United States where pears and apples
are grown. 1t was first reported in
the Hudson River valley, N Y. about
1892 and was doubtless indigenous in
the eastern United States. The dis
case has gradually spread westward
as the country became settled and ac-
cording to Waite became known in
California about 1Ss5-1S97. Accord
ing to the same author 1t has been
known in British Columbia for almost
the same period. 1t is probable that
the disease has progressed westward
along two rather distinct routes-one
north into Idaho Washington and
British Columbia, the other south in
to California.
In Oregon Fire Blight has appear
ed in two general localities-one in
the southwestern part of the state.
including the Rogue River valley, the
other in the northeastern part. The
former region has doubtless become
infested by the spread of the disease
north from California, while the east
ern part Of the state has been infect
ed through Idaho or Washington
along the northern route.
life Cycle of the Blight Organism.
Beginning in the spring the first
apparent damage produced by the
disease in an infected orchard is the
blighting OF the blossoms. Infection
ton is brought about by insects, prin-
cipally bees, which have visited a case
OF hold-over blight and become COW
cred with the organisms contained in
the sticky exudation, inoculating the
flowers in their search for nectar The
organisms divide and multiply in the
nectar and are able to enter the living
tissues through the unprotected nee
taries. Having entered the tissues
they quickly blight the blossoms, pass
down the blossom stem and into the
fruit spur, killing the tissues and
cutting off the leaves from water sup
ply causing them to shrivel and dry,
thus producing fruit spur blight"
The latter occurs several weeks after
blossom infection. In very serious