Pullman herald. [volume] (Pullman, W.T. [Wash.]) 1888-1989, 1912-07-05
rur FIRE BLIGHT
The OF APPLE AND PEAR
Rex Hunt, Assistant Botanist,
n ah,ngton Experiment Station

entity received 50 many 0oni pl"i" .
~ images resulting from attacks of
q s,,oht that it seems imperative
~, ~ every precaution be taken If an
,,o,n,c of this disease is to be
srolded. Three years ago number
:, orchards and hundreds of indi-
traes were ruined in a single
.munity of this state by fire
~ The following short account
~ disease and control methods is
siven in the hope that it may aid in
.oventing another serious epidemic.
MIRO blight is caused by bacteria
-,,ob work Just beneath the bark of
~ tree. Infection usually takes
.loca through the blossoms or
,h,ough the tender young twigs. In
.ooto get some of the bacteria on
hair feet or mouth parts and spread
IAN from blossom to blossom. The
hootoria multiply rapidly in the
honey of the flower, grow down into
tho spur and attack the limb. Other
nsocts with infected mouth parts
hto into the twigs or water sprouts
and thus spread the disease. In pear
.,oos the diseased leaves and twigs
usually turn dark brown or black, as
,bough charred by fire. The fruit
on affected branches often turns
black also, sometimes exuding a
mmmy substance which is made up
entirely of bacteria. The appear
once of the disease on the pear is SO
Characteristic that it is usually cas-
ily recognized. On apple trees, how
ever, the leaves and twigs are often
only slightly discolored and are sell
dom extremely dark colored as in
the pear. On this account the or
chardist often experiences difficulty
in deciding whether his trees have
fire blight, are spray scorched or
have been subjected to some other
adverse condition. The writer dis
covered a simple means of diagnosis
which has, so far, at least, never
failed when several specimens were
at hand. The method is simply TO
examine the tender tips of affected
twigs and the stems of affected
leaves for beads of gum. These
beads are often so small that a care
full search is necessary in order to
locate any, but if fire blight is pres
ent they can be found. If one of
these beads is dissolved in a drop of
water and examined under a micro
scope giving high magnification, it
will be found to consist of countless
numbers of the bacteria.
The blight is not always confined
to the blossoms and twigs. After
gaining entrance through a blossom,
an insect bite, or other wound it is
quite likely to go down the tree,
sometimes killing it to the ground in
very short time. In California it
was found that the disease killed
many trees by going down water
sprouts to the roots of the tree.
The bacteria live over winter in
many of the infected branches and
provide a source of infection in the
spring This hold-over blight is
more often the result of late infec-
u0ns which do not develop very far
III the fall. Twigs and spurs on the
uunk and larger branches seem par
ucularly liable to infections which
i've over, forming cankers in the
spnhg' These cankers are often the
"urce OF Infection in orchards that
were otherwise carefully pruned in
4 the fall.
When the disease appears in an
Oichard 1t should be taken in hand
y once and every sign of the disease
nuheu out. In case of an epidemic
10 not always possible to take out
VERY infected twig, but at least all
injections that threaten the main
anOS should be kept pruned out. If
~ are any spurs or TWICE near
'ne trunk of the tree they should be
p'uaed out. In pruning out diseased
nnOs 1t should be remembered that
pacterla are further along
.u7 Dark than the dead or discolored
A'A SHOWS. The cut should always
= made at least eight or ten inches
r''0" the lowest sign of the disease.
~ not leave long stumps, etc, any
than you would in ordinary
s.uung. Be very careful to steril-
!, e'ery cut or wound. A solution
sO'rosiVe sublimate l to 1000 or
no.. sA'oolc acid solution may be
lns ior sterillzing. Carry the So
q. III glass or enameled vessel.
anos Tue sponge onto the wound hard
noss 10 drive the solution into the
sho,, fhe pruning instruments