Southeastern U.S. Vegetable Crop Handbook - 2022 - 122

ticipating in the National Clean Plant Network for Sweet Potato:
NC State University, LSU AgCenter, Mississippi State University,
University of Arkansas at Pine Bluff, UC Davis, University
of Hawaii. Please contact your local Extension office for more
information.
Presprouting. Presprouting is a technique that produces two to
three times more slips than seed stock that is not presprouted.
Some refer to presprouting as " waking up " the sweetpotatoes
after they have been in storage. Presprouting encourages more
prolific sprouting in roots. This can decrease production costs
by decreasing the amount of seed stock required. In addition to
increasing the number of slips produced, presprouting produces
slips faster. Conditions required for presprouting are similar to
those required for curing sweetpotatoes. Presprouting involves
placing seed stock in a controlled storage area, such as a curing
room. You must be able to control temperature and relative humidity
and be able to provide ventilation. Be sure that you are
able to replace the air one to two times per day because the roots
require a significant amount of oxygen to facilitate presprouting.
A rule of thumb: if there is not enough oxygen for a match
to stay lit, there is likely not enough oxygen for the sweetpotatoes.
To presprout, place seed stock in a presprouting room for
21 to 35 days at 70 to 80°F with 90% relative humidity. Spraying
the walls and floors with water two times per day can help
maintain relative humidity. Mechanical humidifiers (automatic
humidifiers, misting systems) can help establish and maintain
the required relative humidity. Avoid humidity near 100 percent
or wetting of the surface of the roots as this can lead to the development
of rots.
Bedding. Provide 4 to 5 pounds of 8-8-8 or 10-10-10 type fertilizer
per 100 square feet of bed area. Treat seed with appropriate
fungicides to prevent bedding root decay. After presprouting,
place roots into beds, being careful not to damage them. Be
sure to cover roots completely with 2 to 3 inches of soil. Do not
be concerned if a few sprouts are above the soil line. Keep beds
moist but not wet. After planting roots, cover beds immediately
with black or clear plastic to warm the soil. Punch holes in
plastic for ventilation as needed. Slips are ready to harvest when
they have 6 to 10 leaves (8 to 12 inches long) and adventitious
roots are initiated (roots projected from the nodes or joints of
the stem). Slips from presprouted roots are generally ready one
week earlier.
Preparing Slips for Transplanting. To harvest, cut the slips
about 1 inch above the bed surface. Cutting is preferred to pulling
slips. Always pull the knife up and away from the soil to prevent
contamination from the seedbeds from moving into the production
field. Clean knives frequently by dipping them into a 1:1 (v/v)
solution of bleach and water. This will also prevent the spread
of diseases from the seedbed into the field. Set the slips in the
field within three days after harvesting them from the plant beds.
About 500 slips can be produced from one bushel of seed. One
bushel of seed requires 20 to 30 square feet of bed area.
Transplanting. Avoid planting slips until all danger of frost is
past because they are very frost sensitive. Beds should be 4 to 8
inches high and as wide as equipment will allow. Narrow beds
122
tend to dry quickly and may reduce overall yields. High beds
will aid in promoting drainage, thus preventing water damage
to roots. The most economical method to set a large number
of plants is with a mechanical transplanter. Space slips 6 to 16
inches apart within rows spaced 3½ to 4 feet apart on row centers.
The number of slips needed per acre will depend on your
desired spacings. Be sure to manage water carefully to avoid
transplant shock. Slips set more widely apart in-row will facilitate
root enlargement, while closer in-row spacing can result in
increased competition and delay root sizing.
SWEETPOTATO PLANTING DATES
AL North
AL South
GA North
GA South
KY East
KY Central
KY West
LA North
LA South
MS
NC East
NC West
OK
SC East
SC West
TN East
TN West
VA East (coastal)
VA West (mountains)
5/1-6/30
3/15-5/15
5/15-6/15
4/1-6/15
5/20-6/1
5/10-6/10
5/1-7/15
5/1-6/30
4/15-6/30
4/25-5/20
5/1-7/15
5/25-6/30
5/1-6/10
4/15-6/15
5/1-6/15
5/15-6/30
5/1-6/30
5/15-6/30
6/1-6/20
SPECIAL NOTES FOR PEST MANAGEMENT
INSECT MANAGEMENT
Lepidoptera Larvae: Sweetpotato hornworm, corn earworm,
southern armyworm, yellowstriped armyworm, beet armyworm,
fall armyworm, and soybean looper all feed on foliage leaving
small to large holes. In plant beds and newly set fields, damage
may be serious. Mid to late season foliar feeding may reduce
yields or delay sizing of roots when coupled with plant stress.
After harvest, larvae may continue feeding on sweetpotatoes left
in the field and in storage. Apply insecticide to plant beds and in
fields as needed. Cuttings should be free of insects before planting.
Where worms are abundant at harvest, spray fields 2 to 3
days before digging. Remove harvested sweetpotatoes from the
field immediately.
Cucumber Beetles (rootworms): Adults and larvae of the
banded cucumber beetle, Diabrotica balteata, and the spotted
cucumber beetle, Diabrotica undecimpunctata feed on sweet
potato. Both species are highly mobile and will also feed on several
other host plants including, various vegetable plant species,
soybeans, and corn. Adult beetles feed on sweet potato foliage,
creating irregular holes in the leaves. Adult beetles lay eggs in
the soil and larvae developing in the soil feed on developing
sweet potato roots. Feeding on the roots can occur throughout the
production season, but damage from these insects increases late
season. Feeding injury results in unsightly blemishes on the roots
at harvest. The larval stage lasts from 8-30 days depending on the
temperature and food supply. Pupae are found just below the soil
2022 Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2022

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