Tensas gazette. [volume] (St. Joseph, La.) 1886-current, 1917-08-10

Crop Rotation.-Healthy plants may
be grown by careful seed selection and
proper care in the preparation of the
hOtbed, but If these plants are set in
soil that is infected with disease, much
of the effort coward control is wasted.
Sweet potatoes should be set In new
ground or ground upon which potatoes
have not been grown for several years.
1t is not known how long the fungus of
stem rot will live in the soil in the alb
Sence of sweet potatoes, but If they are
not planted oftener than once in four
years the fungus will undoubtedly be
greatly reduced.
Black Rot (BIack Shank, Black Root).
Black rot is caused by the fungus
Sphaeronema fimbriatum and may oc-
cur on any underground part of the
plant. On the potatoes the disease Is
characterized by dark, slightly sunken,
more or less circular spots, while on
the stems it appears as small black
spots which soon enlarge until the
whole stem is rOtted off. On the pO-
tatOes the surface of the diseased spots
is of q metallic luster and just under
meath the spots the tissue is green.
When cooked the potatoes are very bit
ter.
ControI.-Black rot is disseminated
i'm about the same general way as stem
rot, but unlike stem rot ii spreads free
ly I'm the storage house if conditions
are favorable. The fungus may be
spread in the storage house by handling
the potatoes, by settling in the bins,
and by flies and other insects which
may carry the spores on their bodies.
The same methods of control used for
stem rot will control black rot, en-
phasis being laid on preparation of the
hotbed. proper selection and handling
of seed, and crop rotation. Where
black rot is prevalent the potatoes aft
er being dipped should be picked over
carefully, and all that show suspicious
looking black spots should be discard
ed. Treating the fields with lime, sui
phur, etc, has no effect on the disease,
and dipping the plants in bordeaux
mixture or lime-sulphur mixture is not
to be recommended.
Foot Rot (Die-OfD.
This disease is caused by a fungus
called Plenodomus destruens. The dis.
ease first appears as small brOwn-tO-
black spots on the stem of the plant
near the soil line. These spots spread
very slowly, but eventually girdle the
plant and extend or 8 inches up the
stem.
Controi.-FoOt rot is distributed In
the same manner as stem rot and black
rot. but unlike black rot it does not
cause heavy damage in the storage
house. Proper seed selection, care in
preparing the hotbed. and crop rotation
will aid in controlling foot the same a.
stem rot and black rot.
Scurf (SoiI Stain, Rust, Jersey Mark)
This Is disease caused by thu
fungus Monilochaetes infuscans and |:
characterized by brown discolOratior
of the surface of the underground part!
of the plant. The discOlOred areas ma!
be spots of varying size and shape. o.
there may be a uniform discOlOratiOi
of the entire surface of the potato
Control.-The fungus lives through
the winter on potatoes in storage an,
on decayed vines left in the field. /
infected potatoes are used for seed, tn
fungus grows from them onto tn,
plants and is carried to the field. N
injury Is caused to the plants i'm tn
bed or in the field, but the growth fol
lows down from the stem of the plan
to the potatoes. Dipping the seed a
for stem rot will destroy all spores tina
} may be on the surface of the potatoes
Deep, clean cultivation, crop rotation
and the selection of disease-free see
J potatoes will aid in controlling scuri
Soft Rot
Soft rot is caused By q mold know
, as RhizOpus nigricans. and this fungi
} is one of the most destructive disease
in the storage house. The fungus eI
( tiers at one end of the potato and grow
: rapidly. With high temperature an
+ relative high humidity few days an
t sufficient to destroy the entire potato
' The potatoes become soft, watery an
stringy at first. but as the mOisture !
r the roots evaporates they become har
= and brittle. When the skin is rupture
while the potato Is soft moldy grOwt
: appears on the surface. The spores {
5 the fungus may be spread by handlin
: the potatoes. or they may be carrie
t about the storage house by flies and IL
!. 1sects.
Y Control.-Careful handling of the p,
] tatoes when stored, so as to avol
: bruises, and proper management Of III
$ storage house. as recommended unds
f Storage" will aid in controlling so
rot.