Milford chronicle., 1891-03-13
New Ieraey REperlmant station.
SOME FUNGoUs DISEASES OF THE SWEET
POTATO. BY BYRON D. HALsrED.

POTATO. BY BYRON d. HALSrED.
This is the FIRST bulletin to discuss the dis
eases Of the sweet patato, and yet nine def
mite and serious diseases are described. This
is an illustration of the hidden or obscure
difficulties with which the farmer has labored
aud it is an excellent instance, also, Of the
manner in which the stations are coming to
his aid. The existence ofthe sweet potato
diseases is itself sufficient reason for the es-
tabiishzeut ofan experiment station in New
Jersey.
The soft rot (Rhf=obHs NigricaHs)is most
destructive in the store room, although it
may be found in the field at digging time.
The tubers quickly become soft and worth
less. The mould usually enters the tuber
through the upper extremity, where it is
severed from the main root.
SOFT ROT OF SWEET POTATO.
''The mould fungus that causes son rot is
very contagious by contact, as every grower
Of sweet potatoes who has suffered from the
trouble we'll knows. It is quite safe to as
sumo that the mould makes its entrance to
the rost from the surrounding medium, and
usually after the roots are harvested. II does
not, so far as known begin BY injecting the
leaves as the growing plant, aud thea pass
down the stem, as is true with the soft rot Of
the white or Irish potatoes. That it comes
from withoutthe plant. and fuds any broken,
bruised or cut spot in the root favorable
place for entrance, suggests the importance
of being careful in the harvesting and subse-
quent handling, that the least possible harm
shall come to the skin Of the roots. itisalso
true that the soft rot is greatly favored by
moist atmosphere, especially shortly after
digging, at the time when the roots are under
going the process Known as sweating" At
this critical period it is very important that
the potatoes be stored in well ventilated
artificialiy-warmed room, that maintains
temperature ofnot far from seventy
degrees, or about that of living room. Those
growers of sweets" who keep their crop for
the late market, or hold the roots until spring,
are of one accord, that to avoid the soft rot,a
stove or furnace is au essential part Of the
furniture of the storage cellar.
The black rot (Ceratocysfis Jf1s6riafa) is
one ofthe most destructive sweet potato dis
eases, and its habits are obscure. It's dry rot.
The rot begins at a certain point and gradu
ally spreads in all directions, until the
whole root is decayed. When the patch is
Of the size of halfdollar or so, it begins to
break up at the center, as indicated by the
darker irregular places in the middle Of each
decayed spot. The black rot is usually evi-
dent in the roots at digging time, but many
ofthem are so little affected then that they
6nd their way into the market and any
further loss from the increase of the decay
falls upon the middlemen." The disease
first appears upon the young plants, usually
in the hot-bed. The shoots are affected with
a black rust, and spots of the same stand
upon the root Badly rusted plants are
always discarded by growers, but the
slightly diseased ones escape attention, and |
he fungus develops upon them during the
whole season. These diseased vines are |
Usually feeble. The disease is eommuni |
,ated from the vines to the tubers.
BLACK ROT OF THE SWEET POTATO.
''From the investigation ofthe subject it
s seen that the black rot fungus is abun-
lantly supplied with Spores and they may
,e found in one or more forms in every
,atch of diseased substance in the root or
prout. These spores, being formed under
,round, as a rule, tend to charge the soil
With the germs of infection, How long the
pores can remain alive and inactive is not
Known; but very likely for many years, and
he roots of one crop may become inocu-
ated from the fungus of crop upon the
anne soil. In like manner, the spores being
ight as dust can be carried from one field
o another by the winds. The difficulties Of
.pplying satisfactory remedy are not easily
,vercDme, for the trouble is so largely under
round. In the first place, there no doubt
hat only healthy sets should be used, which
means the careful selection Of perfectly
ound roots for the hot-bed In order to get
he best plants, it is possible to use some
emedy in the hot-bed, as, for example,
of copper, the Bordeaux mixture,
r similar substance which will tend to keep
he sprouts from outside contamination.
there is also something in the setting OF
he plants, fof if they get poor start, as
rom chilling rains, they are weakened, and
hereby made more susceptible to the attacks
f the black rot. It is not to be considered
hat the circumstances of the season or con-
itions fthe soil are in any sense the cause
f the black rot, as a specific fungus is neces-
ary for that; but it. like all other living
hings, is dependent upon its surroundings.
t is possible that certain kinds Of manure,
s heavy cow-dung, for example, are more
to the development ofthe rot than
orse manure, and a commercial fertilizer
nav be better than either. Such questions
nust be settled by a thorough testing made
d the field. It seems impracticable to ap-
,Iy any substances to the soil to kill the
erms that have accumulated there As a
ule, the only way is to let the fungus starve
ut, by withholding the crop upon which it
eeds, until the germs become extinct.
While a grower with superior sweet potato
and may be loath to set aside his best crop,
here is no doubt that in some cases, in the
ong run, 1t would be the most economical"
Soil rot is perhaps the most serious
nd obscure of the sweet potato diseases.
The roots are attacked when young, and the
diseased portion ceases to grow, causing the
uber to become CONSTRUCTED or knotty or var
ously misshapen. The fungus exists in the
oil, and attacks plants which are perfectly
lealthy when set "From the conditions
hat surround the growth and preservation
# this soil rot fungus, it is likely that it can
lot be eradicated by any Of the ordinary
Methods ofspraying with copper compounds.
/ is most emphatically in the soil, as every
weet potato grower well knows. With the
lack rot, it has been shown that one Of the
reat precautions is to have perfectly healthy
prouts; but this will avail almost nothing in
he case of the soil rot.