The ranch. [volume] (Seattle, Wash.) 1902-1914, 1906-06-15
PEAR BLIGHT OR FIRE BLIGHT
BY r. Kent Beattie, Botanist at Wash
ington State College.

ington orchardists, pear blight is not
new disease. For many years it has
caused trouble to growers in the east
ern United States. In some regions
orchardists have gone out of the pear
business several times during the last
hundred years because of pear blight.
Everywhere it's appearance has been
serious menace to the growing of
| this fruit To a less extent 1t also
affects the apple.
The disease reached Washington
several years ago. 1t was first called
to the attention of the experiment sta
ton by J. F. Lafollette, of Wawawai,
Whitman county, in the spring of
1900. A serious outbreak of the dis
ease in his large orchards caused the
loss of practically all of his Idaho
pear trees and destroyed that years
crop of Bartletts. A year or two
later it spread to the upland orchards
of the Palouse country, and since
little effort to combat the disease was
made they are now nearly all de-
stroyed
The symptoms of the disease are
so characteristic that there is little
difficulty in recognizing it in the field
Beginning near the tips of the
branches or on fruit spurs the leaves
and stems turn black. This black
ening travels down the stem at
rapid rate, under very favorable cir
cumstances as much as foot a day.
1t passes from the smaller branches
to the larger ones, eventually reaching
the main trunk. The trees rapidly die
The result is that the tree looks as
if fire had swept over it.
The cause of this disease is well
known. Several years ago it was dis
covered and the work of the parasite
was studied. The work was chiefly
done by the United States department
of agriculture. 1t was found that the
disease was due to the attacks of a
| bacterium. Bacteria do not cause
many plant diseases. Their injurious
work is chiefly felt by animals. Near
ly all of our contagious or infectious
human and animal diseases, such as
smallpox, diphtheria, tuberculosis, etc.,
are due to bacteria. This bacterium
however, lives upon a plant. When it
gains entrance to healthy trees in the
conditions are favorable, it multiplies
very rapidly by division. 1t lives in
the growing layer of the tissue (called
the cambium layer just under the
bark. It's attacks upon this tissue
cause the cells to turn into a black
an affected limb. The slime is filled
with millions of bacteria.
The disease is carried from tree to
tree chiefly by insects. In the early
spring the insects get the germs from
the slime which OOzes from cracks
and injuries on infested trees. 1t
gains entrance to healthy tree in the
buds, flowers and tender growing
points visited by the insects The dis
ease is also often transferred by care
less pruning The cutting of a knife
into a diseased limb and then into
healthy one is likely to transmit the
disease.
Pear blight winters by working SLOW
ly into various parts of the orchard or
by working upon other plants, such
as the apple and wild thorn. Wild
brush or plants related to the pear,
growing near a pear orchard, should
be removed.
When the blight is in an active con-
dition the slime under the bark is in
LIQUID condition and the diseased
and blackened portion shades off grad
ually into the healthy tissue. When
the blight is dead, the slime dries
up and the blackened tissue is sep
arated from the healthy by sharp
line.
How to Treat.
There is but one remedy, and that is
proper pruning. No spray is known
to have any value. AS soon as the
disease appears, prune it out. Take a
knife and cut through the bark at
various places and determine how far
the disease runs down under the bark.
VI; &c, ga inn rYtI n