Yorkville enquirer. [volume] (Yorkville, S.C.) 1855-2006, 1910-04-22
NO. 80.
BLACK ROT.
Clemson Extension Work Explains Dis
ease of Sweet Potatoes.

Clemson Extension Work Explains Dis
ease of Sweet Potatoes.
One Of the most wide spread and
most destructive diseases in this
state at present Is the black rot Of
sweet potato. This disease occurs
quite commonly and does considerable
damage on potatoes both in the field
and in storage. The rot is caused by a
parasitic fungus, which, under certain
conditions, is able to pass from one
plant to another and thus spread the
disease
! The trouble first appears as brown
or black patches or mottled, discolored
areas on the surface Of the potatoes.
Quite frequently these discolored areas
are observed in potatoes when they are
dug. but at this stage the disease only
seems to penetrate the skin and Is ap-
parently doing no serious harm. Later
the rot extends into the potato and
causes the affected area to turn black
and to emit the odor which Is so char
acteristic Of rotten potatoes. When
such potatoes are stored in warm, moist
places, the rot producing fungus be-
comes especially active and by means
of tiny spores, which are produced in
small black pustules on the surface Of
the diseased areas, spreads rapidly
from one potato to another. Under
such conditions the disease is also
spread by the filaments Of the fungus
faf fn
into adjoining healthy potatoes. In
this way the rot might spread to ev-
cry potato in bank
II slightly diseased potatoes are
stored in a place where conditions are
unfavorable for the development Of
the rot, they frequently remain partly
rotted until spring. The real danger
Of spreading the disease from one field
to another comes in bedding such pota-
toes. Slightly diseased potatoes seem
to sprout as readily as healthy ones,
and the slips from such potatoes are
diseased.
The disease transferred with such
slips to the field remains on the plant
develop. The fungus which causes
black rot also lives over in the soil
from year to year and where potatoes
are planted every year on the same
land, the disease constantly gets worse.
To prevent black rot then we must:
First, secure disease-free seed for
planting. Second, avoid planting pc ta-
toes on the same land for two years in
succession.
Quite frequently 1t is impossible to
secure potatoes for bedding which are
entirely free from disease. In such
case it Is well to use vines instead Of
slips, for the fungus which causes the
disease remains in the vicinity Of the
roots Of the plants. 1t does not live in
the vines and leaves, 80 vines grown
from diseased potatoes, II planted on
land which Is free from disease, will
produce sound potatoes
Now, as 1 have said, black rot oc-
ours on the majority Of the farms in
this state, and Is responsible either di-
rectly or indirectly for the loss Of thou
sands of dollars worth of potatoes an
nually, so it is well for every farmer
to look out for 1t and guard against its
spread. II you have already bedded
your potatoes and are not sure that
they are free from disease, plant as
much Of your crop as you can from
vines and on land not previously plant
ed in potatoes. When you gather these
potatoes, bank separately the ones
grown from the vines and the ones
grown from the slips and note the
keeping qualities Of each.
Potatoes should not be banked for
two years in succession in the same
place, because the fungi which causes
these rots will live over in the old
banks and attack the new potatoes "a
soon as they are banked. Where pota-
to houses or cellars are used for stor-
ing, they should be cleaned out and
disinfected before the new crop Is put
in. This can be done by cleaning them
out thoroughly and then spraying the
walls and floor with a per cent So
luton of formaline or per cent solr-
ton of copper sulpnate (blue stone).
II. w. Barre.
BOtanist S. c. Experiment Station.