The Yakima herald. [volume] (North Yakima, W.T. [Wash.]) 1889-1914, 1905-11-29
THE PEAR BLIGHT.
Micrococus MISUNDERSTANDING
Treatise on the Subject.

Editor Herald: Again we are con-
fronted with the TACT that eastern
nurseries are determined to make
this state the dumping ground for
their infected trees. Thanks to the
vigilance of our state and county in
spectors, we have so far escaped one
of the worst pests that could posi-
bly, have been introduced into our
valley-the pear blight.
What is it? Until recently there
were innumerable theories as to the
cause and cure of the disease; but,
thanks to the investigations of Pro-
fessors Burrill and Arthur, we know
that it is due to the presence Of a
specific germ of the bacteria-so
minute as to require the aid of a
powerful microscope to see 1t. Pear
blight is easily distinguished from
other maladies. Limbs affected by
it become dead and blackened, to-
gether with the leaves, flowers or
fruit they bear. The injury may be
confined to one or a few limbs, OF
may gradually extend to the whole
tree The twigs of apples and GER
tain other pomaceous fruits are also
liable to this disease. The germs of
pear blight are so minute that they
are carried through the air by the
slightest wind. They seem to be un-
able to penetrate healthy bark, but
gain access to the interior of the tree
through the blossom. They alight
upon the sticky surface of the inside
of the flower cup, and are able to be-
gin developing there, passing down
through the stem to the twig below
The germs can also gain access
through the tips of growing branches
where the green growth is sOf. and
succulent, and no doubt they occas-
ionally enter through cracks in the
bark.
After the bacteria have gained ac-
cess to the tissues of the tree they
multiply rapidly, and generally in the
course of few weeks they have be-
come so abundant as to show their
presence by blacken:ng the bark or
the blossoms AS the disease pro-
crosses, Professor Arthur says, the
germs exude on the surface, and the
gummy substance thus produced is
washed off, the gum is dissolved and
the germs set free and washed into
the ground The germs multiply
there in the rich mould, and grow
all winter, or year after year.
In dry time the wind takes up
the germs into the air, or they may
be taken up by simple evaporation.
Now, when the surface of the tissue
is tender and moist, as in spring, the
air, laden with these germs playing
over the trees, brings the germs in
contact with the delicate tissues.
The germs are held there by the
moisture. and enabled to grow. The
disease gets foothold, and in the
course of a month or two it shows
itself by the sudden blackening of
the leaves. Insects also carry the
germs to the blossoms.
| Treatment: No successful meth
cd of preventing the diseases by ar
tificial APPLICATION to the trees has yet
been found. But it has been shown
that If the trees are carefully watched
during the season of growth, and
the affected twigs cut OF Eat least
foot below the lowest point of In
jury) and burned, the damage done
may be greatly lessened. My advice
however. as a nurseryman of fifteen
years experience, would be that un.
der no consideration should nursery
stock affected by the blight, no mat.
ter how slightly, be bought. The
trees may show indications Of pear
blight, and such stock should be al
once burned; for If the disease IL
once generally introduced into the
country, you may as we'll write finis
SO far as the pear is concerned. A
word to the wise Is sufficient.
| PAUL G.. KRUGER.