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

however that any disorder Of the root
J system, whether due to pear blight
or some fungus or physiological dis
ease will have similar effect on the
foliage. Whetzel has pointed out that
when the apple is badly cankercd,
either on the larger limbs or trunk
the foliage is pale green or grey, more
or less dwarfed and curled, condf-
/ ton which has been called by grow
ers mouse ear"
The pear and apple tree are cover
ed by a protective layer Of tissue, the
cuticle, through which tn blight or
ganisms cannot enter. except the nee
taries and stigmas in the blossoms
and actively growing tips Of branch
es. Therefore except in cases of
| blossom infection and some cases Of
twig blight the germs can enter only
| through wounds which expose the
sappy portion Of the bark. Wounds
may be caused i'm various ways
punctures of insects, birds (sap suck
ers), gnawing Of animals. barking or
otherwise wounding by careless farm
! hands in cultivation pruning or pick
| ing Germs may also enter through
growth cracks.
Method OF Spreading the Disease.
The Fire Blight germs are natural
ly disseminated chiefly by insects at
blossoming time as described above.
Insects may also carry the germs to
wounds on the branches or trunk. II
| is probable that a portion of the in
fection of the twigs resulting in twig
blight may be brought about by insect
punctures. The feet Of birds may be-
come infected with blight germs and
the disease thus carried long distances.
Sap suckers may "tap" an active
canker and carry the germs to unin-
fected trees. Typical cases Of body
blight have been traced by Waite to
this sort Of infection. Rain may wash
the germs from the ooze Of active cank-
ers to wounds, insect punctures or
growth cracks lower down on the
branches or trunk Of the same tree.
One of the most fruitful sources of
infection has been by the pruning
shears or saw. In pruning, II an ac-
tive canker is cut into, the tools be-
come infected and serve as inoculat-
ing instruments to spread the disease
throughout the orchard.
Infection may spread very rapidly
from one district to another along
highways where Seeding apples and
pears are allowed to grow unmolest-
ed Seeding trees springing from
fruit cores thrown from car windows
make Of the great overland railroads
n natural and easy road over which
Fire Blight may travel for long dis
tances through unsettled regions. This
is one of the possible ways that the
most favored valleys, naturally iso-
lated by mountain barriers, may be-
come infected.
Conditions Favoring the Disease.
The disease is more prevalent in
orchards which are rapidly growing
and in a succulent condition due to
naturally rich soil, abundant cultiva-
ton or application of nitrogenous fer
tiliZers Heavy winter pruning has
n tendency TO stimulate rapid and
succulent growth and renders the tree
more subject to the attacks of the
blight. Irrigation should be reduced
to the minimum in infested or
chards.
Method of Control
The only known method of con-
trolling Fire Blight is to cut out all
eases of hold-over cankers wherever
they appear Spraying with fungi
cides is of only supplementary value
and the various "blight cures" are
worse than useless and 1t is a waste
or time and money to apply them.
Experience has shown that it is of
little permanent value to attempt to
cut out the fruit spur and twig blight
as thcy appear. Unless these forms
Of the disease extend into the branch
es on which they occur and canker
is formed the disease usually becomes
naturally limited and the germs grad
ually die. due to drying out of the
canker so that at the beginning of the
dormant season very few such cases
show live germs present.
The efforts of the grower should he
directed to cutting out all cases of
blight Canker and body canker dur
ing the fall, winter and early spring
when the cankers have become more
or less limited in their growth and are
not actively spreading.
summer cutting intelligently APP
piled is frequently of great value par
ticularlN where there is only a little !
blight In the autumn before the |
leaves fall is a good time to do the |
cutting as all cases of twig blight are |
easily observed and the condition of |
the foliage as already described, Of |
fers a convenient method of determin- |
ing the presence Of cases Of root rot |
or collar rot and obscure cases of |
blight canker on body or lower limbs. |
Every orchardist in an infected dis
trict should examine all pear and ap-
pie trees at the time suggested and |
cut out all diseased portions The
trees should be particularly examined
for cases of the collar rot. 1t is this
form of the disease that causes many
trees to be killed outright.
In infected regions it has been
found practical by the most success
full owners of commercial orchards to
keep one or more men in the orchard
during the summer and fall whose sole
duty it is to locate and cut out all
cases of blight canker as soon as they