The Oroville weekly gazette. [volume] (Oroville, Wash.) 1905-19??, 1914-02-13
MENACE TO ORCHARDS
Fire Blight In Pear and Apple
Trees a Disease hat Must
Be Guarded Against

Through the courtesy of Prof. II.
-. Jackson, plant pathologist OF the
Oregon Agricultural College, the Ga
4etLe IS permitted 10 publish a valuable
vuleIun ON "rire Blight OF Pear and
apple, togLner with the Illustrations
srOWIng Lhe characteristics OF the dis
ease, prepared by Prof jackson and
pIInLed last fail by the Oregon Agri-
cultural Press.
While sLre blight has not made its
appearance III the Okanogan valley,
tue disease has occurred in districts
both north and south OF this valley
anu, from It's nature, 1t is wise to take
The necessary precautions to guard
against its gaining q foothOld here.
OF these reasons the following ar
ucle, the first installment OF which
appears herewith, is OF particular in
terest, especially since it is authorita-
ave, anu il is worthy OF the careful
loauIng and consideration OF every Or
chardist in this district:
ire blight is the most serious of
all the diseases which attack the pear
ana apple. IL is a contagious dis
ease OF bacterial origin, which, under
proper conditions, may attack any
part OF The tlee. Besides the pear and
apple, the ounce, wild crab-apple,
nav Jnorns, mountain ash, service
berry ana some other pomaceous trees
are subject TO attacks OF this disease.
Distribution
FIRE blight occurs in more or less
verify III nearly ali parts OF the
ulted states where pears and apples
are grown. 1t was tlrst reported in
The Hudson hlVer valley, N. Y, about
IiJG ana was doubtless Indigenous in
The eastern United states. The dis
ease mas gradually spread westward
as me country became settled, and
according to Waite became known in
California about lS55-lS97. According
70 the same author it has been known
III BRUSH Columbia Tor almost the
same period. 1t is probable that the
disease mas progressed westward
along Two rather distinct routes-One
north into Idaho, Washington and
British Columbia, the other south into
California.
tue blight is known to occur in
oregon at the present lime In all the
counties east OF the Cascade mount
aims with the possible exception OF
Wasco county. 1t has been recorded
III Hood hiver county but has not yet
appeared there in serious form nor
caused any appreclable damage. The
disease Is present in that portion of
tne Rogue River valley included in
Jackson and Josephine counties, and
mas spread north into the UmpQua
valley. No authentic record OF the
disease III the Coast region or in the
" IIlamette valley has ever come to
the attention of the writer.
Cause of the Disease
Fire Blight is caused by a minute
organism belonging to the bacteria
and known technically as Bacillus
1t is ROD shaped mOtile
germ which divides very rapidly by
simple fission and is found in i'm
mense numbers in the diseased It's
sue. The germs are SO minute that
they measure only about 1-25000 of an
inch in length and are visible only
under the highest magnification of the
compound microscope.
PIOOfs Oi the Bacterial Nature Of the
Disease
Myrlads OF germs are present in all
freshly blighted portions of the tree
cankers. Pure cultures of the organ
ism may be obtained from diseased
tissue and cultivated for generation
after generation on suitable culture
media Healthy tissue inoculted with
germs from such a pure culture will
became characteristically diseased.
he 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 artificial infection, are found to
be Identical.
Appearance OF the Disease
The name Fire Blight" is given to
this disease because of the character
isuc appearance of pear foliage on
CWlgs OF branches which have been
allied by the blight organisms The
leaves turn black as though scorched
by fire and frequently remain on the
tree during the following winter. The
foliage of the fruit spurs, killed by
the blight has much the same appear
3nce as that of the twigs. On the
apple the foliage of twig and fruit
spur blight turns brown and dry.
The cankers are also quite charac-
tcrlstic but are very variable in ap-
pearance. dependent on the age of the
branch attacked and upon the condl-
ton of the tree. The disease progress
ses most rapidly in the fleshy outer
layer of the bark and at first pro-
duces watery appearance in the af-
iected area. Later the tissues of the
bark are more or less broken down.
and the cankers which become dark
filled with a gummy substance which
in active cankers eXudes. This ex-
udate is at first sticky and contains
myriads of live germs. 1t is attrac-
tive to insects, which visit such cank-
ers in great numbers and become
covered with the organisms
Besides the blight cankers found on
the limbs and trunks, one frequently
finds larger canker at the surface
Of the ground extending up on the
| trunk for some distance and down
the large roots. This condition is a
form of collar rot" and may result
from blight canker appearing on the
trunk and running below ground, or
may result from infection taking
place through twig blight running
down water sprouts which occur at
or near the surface of the ground.
Wounds made by borers or gnawing
| animals NAV furnish the point of
infection.
Continued next week.