Milford chronicle., 1928-02-17
CONTROL OF SWEET POTATO
WILT

Sweet potato growers throughout
the county and the southern part OF
= the state no doubt will look with
= much interest to the proposed WORK
which is being planned this coming
year by the Department OF Plant
| Pathology of the Delaware Expert
ment Station to devote further study
to the control of the stem VIII
which has been causing consider
able loss to the sweet potato crop
each season in this section OF the
country.
ARRANGEMENTS are being made by
DR.. Thomas f. Manns, Plant Pathol-
ogist and Soil BacteriOlogist OF the
University of Delaware, in co-opera-
ton with the county agricultural
agents and the sweet potato grow
ers in Kent and Sussex counties to
conduct projects and demonstrations
dealing with the control of this dis
ease which is also known as stem
rot" split STEM" and "yellows."
! AS the stem wilt is carried over
from one season to the next in the
seed and also in the soil, it is very
necessary that the growers select
only the seed that is free from this
trouble and practice clean culture
methods in the seed bed. The pres
ence of this disease in the seed may
easily be seen by cutting a cross
section of the infected potato at the
stem end where the infection will
show as a darkened circular area
about one-fOurth inch below the sur
face. In case of light infection the
disease may show itself in the form
of a speckled or peppered condition
throughout the center of the potato,
and when slices of an infected pota-
to are placed in a moist culture dish
in the laboratory the result is
grayish white mold which in the
field kills the roots and stems of the
growing potato thereby causing the
following and whiting plants.
This disease penetrates the potato
so deeply that seed treatment alone
will not control it, consequently,
there is need for careful seed selec-
ton upon the part of the growers.
Seed selection and treatment, how
ever, are of no value unless the seed
bed is carefully cleaned and disin-
fected, since the organisms live overa
in the seed bed and in the open
fields resulting in a sick soil con-
dition 1t is also important that
soil which is used in these beds be
taken from areas that are not in
fected with this disease. After the
seed has been properly selected it
should be treated with corrosive
sublimate which is of great impOr-
lance not only to destroy the wilt on
the surface of the potato, but also to
check the black rot, soft rot, scurf
and poX. This material should be
used at the rate of one ounce to
eight gallons of water, and the po-
tatOes should be soaked in this So
luton for ten to fifteen minutes. This
seed should be bedded early to allow
for early planting in the field, as
only early field planted potatoes pro-
duce slips early enough to mature
good slip seed.
Successful sweet potato growers
have learned that the slip method
Of seed production is the most prac-
teal way of reducing the prevalence :
Of practically all of the sweet potato
diseases. To accomplish this the
seed must be carefully selected for
freedom from disease and bedded :
early, as early planted potatoes r
should produce vines ready for
slipping about the first week in July
under average field conditions. These
slips should. be planted on well fer
tilted and properly prepared land
that is free from all sweet potato
and care must also be TAX
IN to avoil all fields that are poorly
drained. A proper rotation should
likewise be practiced in which the
sweet potato crop will come only
every third or fourth year on the
same land, and areas which are now
infested with the wilt should not be
used for sweet potatoes for a period
Of five or six years.
In addition to the selection and
treatment Of the seed and crop ro-
alton, another very important fac
or to consider in the control of the
wilt is the careful selection of only
healthy hills of potatoes at harvest
line i nthe field. By this method of
selection every potato is known to
laVe come from high yielding hill,
Is well as from one that is free
rom disease. The stems should be
split open to see that no wilt is be-
ng carried in the plant itself, and as
hese infected plants are discovered
hey should be pulled and removed
it once from the field. AS a rule
)lants grown from vine slips will
how little or no wilt, but in sea-
ons with heavy rainfall in July and
august some wilt may show even in
'lants produced in this manner. All
potatoes that are selected for seed
Iecause of their freedom from dis
ase should be selected early and
laced in the best section of the
forage house where they may be
ept in good condition for next
pring's planting in the bed.