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

cases nearly all the fruit spurs may
be bllghted In this way and the trees
set no fruit. Usually the germs die
out and no not grow into the twig or
branch on which the spur occurs but
occasionally the germs may continue
into the bark of the branch at the
base Of the fruit spur and form a
typical canker Fruit spurs on the
larger branches are a fruitful source
of body infection and many cases of
blight canker originate in this way.
Blight cankers may also originate
through infection taking place at the
tip of young actively growing branch
es, particularly IL these be water
sprouts on the larger branches, or
trunks or through infection gaining a
foothold in wounds of any kind. Such
cankers on the larger limbs and trunk
may retain active germs over the dor
mant season and form the so,called
"hold-over" cankers which doubtless
afford the only source of infection for
the blossoms in the spring.
Appearance of the Disease.
The name "Fire Blight is given to
this disease because Of the character
istic appearance Of pear foliage on
twigs or branches which have been
killed by the blight organisms. The
leaves turn black as though scorched
by fire and frequently remain on the
tree during the following winter. 1t
should be noted that this color of the
foliage is characteristic OF the pear
when it has been killed during the
growing season. II a grower not ia
miliar with the pear blight desires to
know how the "twig blight" looks let
him girdle a twig in midsummer and
watch the results. The foliage OF
the fruit spurs, killed by the blight,
has much the same appearance as
that Of the twigs On the apple the
foliage of twig and fruit spur blight
turns brown and dry.
The cankers are also quite charac-
teristic but are very variable in ap-
pearance, dependent on the age Of
the branch attacked and upon the
condition OF the tree. The disease
progresses most rapidly in the fleshy
outer layer of the bark and at first
produces a watery appearance in the
affected area. Later the tissues Of
the bark are more or less broken down
and the cankers become dark in col
or and slightly sunken and are filled
with a gummy substance which in ac-
tive canker exudes This exudate is
at first sticky and contains myriads
of live germs. 1t is attractive to in
sects which visit such cankers in
great abundance and become covered
with the organisms. II after becom-
ing infected in this way they visit the
blossoms for nectar they inoculate the
blossom with the germs which find
an easy access to the tissues of the
blossom through the nectaries.
Besides the blight cankers found
on the limbs and trunks one frequent
ly finds in some varieties of pears
and Spitzenberg apples a larger can
ker at the surface on the ground ex-
tending up on the trunk for some
distance and down the large roots.
This condition is called collar rot"
and may result from a blight canker
appearing on the trunk and running
down into the collar. or may result
from infection taking place through
twig blight running down water
sprouts which come off at or near
the surface of the ground. Wounds
made by borers or gnawing animals
may furnish the point Of infection.
A foot rot may be caused by the or
ganisms gaining entrance to the bark
of roots through infection in the tips
of water sprouts which come off
some distance from the tree. This
condition is common in some varieties
OF pears.
4 pear tree when badly cankered is
easily recognized at a distance in the
early autumn by the general reddish
cast to the foliage. When the foliage
of only part of the tree is reddish
it indicates that a large canker has
wholly or partly girdled one of the
large branches. If the foliage of the
whole tree is equally affected we
should look for a canker at the coll
lar or roots. 1t should be mentioned,