The Kennewick courier. [volume] (Kennewick, Wash.) 1905-1914, 1912-05-17
PEAR BLIGHT

PEAR BLIGHT
The following article is taken from
the report of the eighth annual con-
vention OF the Washington State
Horticultural Convention which was
held at Charleston, in January, this
year. The report is bound in a
volume of some $50 pages and con-
tains many articles that are of time
ly and important interest to every
horticulturist in this state. The
part we reprint is but one section
on this particular subject.
Mr.. Storland, deputy inspector
states that there are some signs of
the blight in this section, and sug-
gests that the growers read the ar
ticle closely, so that they may be
able to detect the disease.
EXTERNAL APPEARANCE
The blight usually attracts attention
in the spring of the year, and a
month or 40 after the blossoming
period. 1t is then found that the
flower clusters are shriveling and
dying; however. if examination has
been made very carefully, the
blighted blossoms may be seen to
have been infected for some weeks
previous to this time. The twigs
will also be found to be dying. In
some cases the new shoots are seen
to be attacked at the tip and the
disease is running downward, kill
ing the tender twigs completely and
running down the bark of the twigs
and branches in the form of an
ooze, which is Shiny in appearance
and somewhat sweetish to taste.
Usually blossom blight accounts for
the greater part Of the infection
points, but in some cases twig in
lection exceeds blossom infection.
If the season is favorable and the
other conditions are just right the
disease may not run further than a
few inches. 1t may kill only the
blossom clusters or the fruit spur
a few inches down the twig and
then stop. On the other hand if
conditions are very unfavorable for
the tree, which means favorable to
the blight germ, the disease may
run down into the main limbs and
branches and in extreme cases may
continue running downward thru
the growing season until it reaches
the ground. Often it has progressed
much further in the bark of the
branches than appears on causual
examination, tor as a general rule
it works only in the bark and cam
blum layers, leaving the mature
wood unframed. Sometims a very
small strip of cambium is left un-
harmed and the sap therefore is
able to continue to flow upward 80
that the leaves and branches may
still carry their foliage or often ma
ture their fruit. Very often, too,
the bark and cambium may be COM
pletely girdled, but the young wood
is still able to conduct enough sap
to keep the foliage and fruit hang
ing, and often allowing the fruit to
mature.
On microscopical examination of
the diseased tissues they are found
to be completely filled with count.
less millions of minute germs. These
germs are mixed with a gummy.
sticky material formed by the sap
of the tree and is produced by the
decomposition of the tissues The
disease is therefore more in the
nature of fermentation or perhaps
we may say a gangrene of the bark
and cambium produced by the in
vasion of this immense swarm of
bacteria. The bacteria proceeds in
all directions from the point of in.
lection; that is, when they go down
twig or spur or water sprout in
to the branches or bodies of the
trees there is a development of the
disease from this point upward and
downward and laterally. On &C.
count of the vessels and fibers of