Judith Gap journal. [volume] (Judith Gap, Mont.) 1908-19??, 1912-03-15
Dry Rot or Stem
Blight Of Potatoes.
BY n. e. Morris, Assistant Bot
anist and BacterioIogist, Mon
tana Agricultural College.
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/. Many inquiries have been received
US to the cause of the whiting and APP
oparent death of potato vines in yari-
-Uus sections of the state. Judging
from the numerous specimens which
nave been sent in to the Experiment
Station for examination, the main
cause of the trouble is dry rot or stem
0light.
: This disease is caused by fungus
known to scientists as Fusarium oxy-
Sporum. The trouble first becomes
noticeable when the plants are about
sDne foot high, although this may vary
TO some extent. In some cases
younger plants may become affected,
while in others the plants may be al.
most mature before any symptoms ap.
gear.
The leaves of the affected plants
have light green color, and later as.
Fume a dull. unhealthy appearance,
with more or less rolling or curling of
4heir margins. Gradually the tops
Kither and fall over, and the vines are
easily pulled up because the roots are
partly dead and brittle. If an under
ground stem is cut crOsswise a brown
color is visible, and this may in some
cases be traced through the tuber
stems and into the stem end of the pO-
cato itself. Examination of these
brown portions of the tuber stem or
potato under a high magnitication
shows the fungus to be very abundant.
The yield from the diseased hills is
diminished, according to when the
plants We're attacked; in some cases
of an early attack the entire crop is a
failure.
When potatoes are dug there is not
much external evidence of disease on
chem, but the majority OF tubers from
diseased plants are, nevertheless, in
3ected. This may be proved by cut
Ting thin slice from the stem end
and searching for the brown discolora-
Zion. If infected potatoes are stored
In cool place but little change will
fake place; if kept in a warm tempera-
<ure a dry rot soon develops. Pota-
toes but slightly affected are not OBJ
jectionable for cooking, provided they
are consumed promptly or kept in a
cool place.
Diseases of this type are very hard
TO control, because the source of in
lection and the fungus itself are un-
derground, hence spraying with fungi
Cides would be ineffective. 1t there
fore becomes evident that preventive
measures must be relied upon in COM
batting this disease. Many such might
be meptionad, but the following are
The most Important:
First-A good seed supply. Avoid
planting seed potatoes which have
come from infected districts. The
stem end of every tuber should be cut
of and inspected before planting to
Insure using only healthy seed.
Second--practice a system of crop
ISOLATION This should be five or six.
fear rotation. Follow the potato crop
with such crops as grain, clover ETC..
avoiding melons, tomatoes. and similar
crops, as these are subject to a wilt
disease that is very like potato wilt.
Third destroy the vines, small pO
tatoes, etc.. after harvesting the crop
Such refuse. ordinarily left on the
ground, affords breeding place fol
the fungus. thus keeping the disease
alive in abundance year after year.
One may ask, what shall do witt
my potato crop from an infected
6eld?" This is an important question
and the suggestion would be to dis
pose of the crop at an early date. I'm
less one has good facilities for storing
In cool, we'll ventilated place, con
siderable loss may occur from the dc
yelopment of the dry rot in storage
As stated before, potatoes slightly al
fected with the disease are not Obje<
tionable for cooking purposes, provi(
ed they are used promptly or else ker
in cold storage. If diseased potatoe
are to be stored temperature of 4
degrees F. or under must be nair
Aoino6