South Bend news-times. (South Bend, Ind.) 1913-1938, 1917-01-21
HOW To CONTROL
POTATO DISEASE
Dr.. H. A. Edison Discusses
Seed-Bed Method of Com
batting Diseases.

Potato diseases, Whlcn are snow
ing a tendency 10 become establish
ed or TO spread in various parts OF
the country. can best be controlled
in most cases through the adoption
by farmers OF the seed-bed method
Of control, according 70 DR.. II. A.
Edison, truck-crop disease specialist
OF the L. * department OF agricul-
ture. In discussing the potato
disease situation and possible con-
troll measures in a recent address,
DR.. Edison said:
"A disease of the potato which is
making it's appearance in several
sections of the country is the one
designated by orion as streak. The
cause of this disease is unknown. 1t
Is characterized by the appearance
of angular spots on the leaves,
which have a tendency TO run down
the veins through the steams Of the
leaflets 10 the main petiole, or leaf
stalk, producing a streaked appear
ance. The affected portions of the
plant wither and die. the leafstalks
break over at the axil Of the leaves
that is. their junction points with
the branches-with the result that
the leaves hang directly down,
swinging in the wind, and attach
ed only by a portion OF the epider-
mis- In severe cases the plants are
eventually entirely killed. The
trouble is apparently transmitted
from generation 20 generation by
means OF the seed tubers. and there
is some indication that it is trans
mitted from plant TO plant in the
field. In the absence Of more def
mite knowledge of the disease, it is
recommended that roguing be prac-
ticed as a precautionary measure
wherever it appears.
Heavy Loss from Mosaic.
Mosaic is assuming great import
ance as a potato disease in certain
sections of the country. 1t is char
acterized by a nothing in the green
OF the leaves. sometimes accom-
panied also by a crinkling but not a
rolling of the foliage. The disease
should not be confused with the un-
even yellowing which results from
the application Of excessive water in
irrigated regions nor with the some
what yellowing and rolling associ-
ated with excessive alkali content in
soils. nor should il be confused with
the condition of partial absence Of
coloring matter, possibly chimaera,
seen occasionally in the fields more
particularly in certain sections of
the west The cause of mosaic has
never been determined, but il is
known that the disease is repro
duced when tubers from affected
plants are used for seed The ex-
perimental data which have been
secured both in the United States
and abroad show that the yield from
mosaic plants is less than that from
healthy plants of the same variety
grown under the same conditions or
ir the same field. The average re-
auction in yield in trials made by
the department with various vari-
cites and in several different sec
tons Of the country is approximate
ly so per cent. Roguing out affect
ed plants in the seed plot affords a
practical though perhaps not COM
plete control of the trouble.
The late blight of the potato
caused by PhytOphthora infestans
and the rot of tubers which follows
in the winter are too well known to
call for description. II has recently
been shown, however, that the
planting of tubers affected with
Phytophthora decay affords means
for infestion OF the growing crop.
The development OF the disease.
however. is entirely dependent upon
weather conditions. In dry seasons
one may plant affected tubers with
out insuring the development OF the
late blight, but it has been shown
that the original infections follow
up the stems from the seed tubers
if the weather conditions are favor
able 70 the development 0f the
fungus. It is, therefore, advisable
TO avoid infected seed when possible
in addition TO employing the usual
control of Bordeaux mixture, which
is a we'll established practice.
Recent studies upon the powdery
scab have demonstrated the fact
that this disease is less serious in Its
character in the United States than
was at first feared. IL is apparently
unable TO survive except in the more
northern sections of the country,
and the damage done there is. in
many years. not serious. The disease
is correlated with heavy, rather wet
soils. or more particularly with sub
soils OF this character. The damage
done is 10 a large extent dependent
upon weather conditions even in
these unfavorable types OF soil.
Decay i'm Storage.
Several species OF Fusarium are
now known 10 produce potato dis
eases These may be classified in
two groups. The first is the wilt
producing group which attacks the
vascular tissues and the root system
Of the plant. cutting of the water
supply and causing injury in pro-
portion TO the extent OF the inva-
sion. In extreme cases a yellowing.
or at least an unhealthy green color
and a characteristic rolling Of the
foliage develop 10 be followed by
sudden whiting and death. The
tubers produced upon infected
plants frequently carry the fungus
in their vascular tissue. as may often
be demonstrated by the appearance