The river press. [volume] (Fort Benton, Mont.) 1880-current, 1911-11-15
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! Dry Rot or Stem
Blight Of Potatoes.
BY n. e. Morris, Assistant Bot.
anist and 6acteriologist, Mon
tana Agricultural College.

~ Is - VsOIIISs NSSVokdVt 0VS"
anist and BacterioIogist, Mon
tana Agricultural College. :.
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Many inquiries have been received
as to the cause of the whiting and ap-
parent death of potato vines in vari-
GUS sections of the state. Judging
from the numerous specimens which
have been sent in to the Experiment
Station for examination, the main
cause of the trouble is dry rot or stem
blight.
This disease is caused by a fungus
known to scientists as Fusarium oxy-
sporum. The trouble first becomes
noticeable when the plants are about
one 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-
pear.
The leaves of the affected plants
have a light green color, and later as
sumo a dull, unhealthy appearance,
with more or less rolling or curling of
their margins. Gradually the tops
wither 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
cfo1nC on6 into thu C&oy,, orI 0f %ho ,a
tatO itself. Examination of these
brown portions of the tuber stem or
potato under a high magnification
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
them, but the majority of tubers from
diseased plants are, nevertheless, in.
fected. This may be proved by cut.
ting a thin slice from the stem end
and searching for the brown discolora.
ton. If infected potatoes are stored
in a cool place but little change will
take place; if kept in a warm tempera.
ture 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 MENTIONED, but the following are
the most Important:
First-A good seed supply. AvoiG
planting seed potatoes which have
come from infected districts. The
stem end of every tuber should be cut
off and inspected before planting tt
insure using only healthy seed.
Second-Practice a system of croI
rotation. This should be a five or six
year rotation. Follow the potato crol
"AtA ouSA SAoPo "o GILL, CAOVV1S SCS'
avoiding melons, tomatoes, and similar
crops, as these are subject to a will,
disease that is very like potato wilt.
Third-Destroy the vines, small pc
tatoes, etc., after harvesting the crop
Such refuse, ordinarily left on the
ground, affords a breeding place fol
the fungus, thus keeping the disease
alive in abundance year after veal
One may ask, What shall I do will
my potato crop from an infected
feld?" This is an important question
and the suggestion would be to dis
pose of the crop at an early date. I'm
less n has good facilities for storing
in a cool, well ventilated place, con
siderable loss may occur from the de
velopment of the dry rot in storage
AS stated before, potatoes slightly at
fected with the disease are not objec
tionable for cooking purposes, provid
ed they are used promptly or else KEEP
in cold storage. If diseased potatoe.
are to be stored a temperature of d
degrees F. or under must be main
tanned.