The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
FOR COMMERCIAL GROWERS
j... ii. .
FLORIDA COOPERATIVE EXTENSION SERVICE
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA, GAINESVILLE
This guide presents general recommendations for
the production of sweet potatoes in Florida.
Modifications may be necessary as improved practices
are developed through research and experience. These
recommendations may vary according to local situa-
tions and growers are urged to consult with their
county extension agent for suggestions and advice in
developing a suitable production program.
Sweet potato weevil regulations have been es-
tablished to control the dissemination of the weevil.
The entire State of Florida is a regulated area and the
regulations are very specific in terms of what must be
done to satisfy the requirements. Growers should ob-
tain a copy of the regulations from the Division of
Plant Industry, Florida Department of Agriculture
and follow the recommendations closely.
Georgia Red-Skin coppery-red and flesh light
orange in color. Good yielder and good plant
producer. Late. Susceptible to fusarium wilt, black
rot, and internal cork. Roots slightly variable tapered
Coastal Sweet-Skin copper and flesh orange in
color. Good yielder and fairly good plant producer.
Centennial-Skin bronze to copper and flesh deep
orange in color. Very good yielder, but poor plant
producer. Early. Some resistance to stem rot and in-
ternal cork. Roots variably tapered to cylindrical.
(Cuban Sweet "Boniato" Potato)-Skin dark
bronze and flesh white. Sparse yielder.
The sweet potato requires a long frost-free season
Insecticides Rates and Use
Insect(1) Spray Dust To Harvest
Armyworms Registrations for toxaphene and DDT
Hornworms (preharvest) have been cancelled. Try 1
Other quart of malathion 5E per 100 gallons of
caterpillars water soon after caterpillars hatch.
Gold Bugs There is no waiting period for malathion.
Wireworms Apply parathion or diazinon at 2 pounds
active ingredient per acre on mineral
soils. Distribute evenly over the soil
surface 2 to 3 weeks before planting and
immediately mix into the upper 6 inches
(1) Begin applications when insects appear; one to two
applications usually are sufficient. Thorough coverage
is difficult where vines are dense, thus, special effort
should be used to provide best coverage possible.
Sweet Potato Weevil-Practice strict sanitation
to prevent sources of infestation and use certified or
1. Seedbed Treatment-Dust with 2% dieldrin.
The first application is to be made when the first
scattered plants show color in the stems. The second
application should be made when all the plants are
up. Additional applications should be made after each
pulling. Apply the material to cover all the soil sur-
face around the plants. Use 1/4 pound of 2% dieldrin
dust per 100 feet of row where field bedded, or 1/4
pound of the dust per 80 square feet where wide
compact beds are used.
2. Production Field Treatment-Before the vines
begin to meet in the middle or the largest roots are 1/2
inch in diameter, use 75 pounds of 2% dieldrin dust per
acre. Apply the insecticide to the soil rather than the
foliage in a 6 to 8 inch band on each row along the
plant crowns. Harvest all sweet potatoes for the fall
crop before December 1 and cull out infested plants.
DISEASES AND CONTROL
Black Rot (Ceratocystis fumbriata)-The fun-
gus produces dark lesions on the underground parts of
the sprouts in the plantbed, and dark, slightly sunken
cankers on the sweet potato in the field and in storage.
The cankers on the potato are, as a rule, not more
than half an inch in depth. Control: Select clean,
disease-free potatoes for seed, rotate crops and
plantbeds. Cuttings (rather than sprouts) from the
seedbed will give effective control. Cut one inch above
the soil line.
Scurf (Monilochaetes infuscans)-This disease
involves only the outer layer of the underground parts
of the potato. It does not cause a rot or reduce yield,
but causes a dark discoloration of the skin. The dis-
coloration may be only a few spots, or may cover most
of the surface of the potato. Control: Same as for
Wilt or Stem Rot (Fusarium oxysporium f.
batatas)-The fungus, in the vascular tissue, causes
the plant to wilt, become yellow and stunted and, if
the attack comes early in the season, the plant may
die. The water-conducting tissues of the potato stem
turn dark in color, often making the stem appear blue
from the outside. Affected stems may crack open. This
disease can be carried in or on the seed potatoes and is
able to live for long periods in the soil when once
introduced. Control: Select clean, disease-free pota-
toes for seed, rotate fields and plantbeds.
Surface Rot (Fusarium oxysporium)-The
fungus produces circular, slightly sunken spots that
are lighter in color than the lesions caused by black
rot. The lesions are quite shallow. Infection takes
place around harvest time and is usually worse in
years when harvesting follows a wet period. During
storage, moisture escapes through the spots and
results in considerable shrinkage and numerous hard,
mummified potatoes. Control: Do not harvest when
soil is too wet, avoid injuries to the potatoes, rotate
Soft Rot (Rhizopus spp.)-The fungus causes a
soft, spongy moist decay during the rotting process.
An abundant growth of gray fuzzy mold is usually
produced on the surface. When the rotting process is
completed, or checked, the parts of the affected po-
tato become shrunken, dry and hard. Control: Avoid
injuring potatoes at harvest. Cure and store under
warm, moist conditions.
Internal Cork (Virus)-Dark spots are produced
within the potato. These spots have no definite pat-
tern in size, number, or location. If the dark area oc-
curs near the surface, its presence may sometimes be
detected by slight indentations, but for the most part,
cutting the potato into thin slices is necessary for de-
tection. Control: Use of internal cork-free potatoes
A limited amount of work has been conducted on
chemical weed control in Florida sweet potatoes.
However, herbicides have and are being tested in the
major sweet potato producing states and neighboring
states as well. There are several herbicides registered
for use on sweet potatoes at the present time. These
herbicides should be used on a trial basis until grower
experience and/or research data can be obtained.
Follow label instructions very carefully.
Herbicides Rates and Usage
10.5 Broadcast soil
time of trans-
1.5 to 2 Needs to be soil
Rate depends on
type of bed
4 Apply overtop
planting. Do not
areas to crops
not on the label
within 6 months
DCPA Post- 10.5 Broadcast soil
(Dacthal) transplant application at
time of last cul-
up to 6 weeks
Sweet potatoes may be harvested anytime after
he roots exhibit satisfactory size and yield. The roots
an be harvested by using a "middlebuster" to expose
he roots for pick up or by using a sweet potato
arvester which is similar in operation principle to the
rish potato harvester. Whichever method is utilized,
Sweet potatoes are subject to injury from root-
knot, reniform, lesion, spiral, dagger, lance, sting, and
ring nematodes. Control measures must be used in
both seedbed and field plantings in areas where
nematodes have been a problem.
Nematicides Rates and Usage
Overall () Row
Fl. oz./ 1000
chisel Gal./ linear feet
per 1000 Acre(2) (Any row
Nematicide Gal./Acre linear feet (36" Row) spacing)
D-D 20-25 59-73 8-10 73-90
Dowfume 4.5-6.0 13-18 1.5-2.0 13-18
Telone 15-20 43-59 6-8 53-73
Nematicide lbs.(3)/acre (36" Row) spacing)
Mocap 80 40 2.8
(1) The overall rate per acre of fumigants is based on a
12-inch spacing. '
(2) These gallonages are given as a guide to determine
total amount of chemical needed for a field. Closer
row spacing will require more chemical per acre;
wider row spacing, less.
(3) Rates are given in lbs. of formulation.
*PRECAUTIONS! Read pesticide labels thoroughly
before opening container and observe all safety precau-
tions. Dispose of empty containers promptly and safely.
Pesticide usage is subject to changes and cancellations.
Keep current on recommendations and regulations by con-
sulting county agents, experiment stations, and industry
Fertilizer Rates and Usage
Soils(1) Basic Application Applications
Pounds Actual/Acre Pounds Actual/Acre
N PO, K,O N PO, KO
Irrigated 60 120 120 10 0 30
irrigated 40 80 80 10 0 30
Rockland 20 40 40 10 20 30
Marl 40 80 80 10 0 30
S1) Sweet Potatoes not recommended on muck and peat
Basic Application-Banded applications (3 to 4
,inches to each side and 3 to 4 inches deep) at the time
Sof transplanting or during early stages of growth
subsequentt to transplanting have been used with
access for many years. An alternative method for
consideration is the use of split applications which
have shown benefit in other crops where high soluble
salts have been a problem. The method involves
placing 1/2 the recommended basic rate of fertilizer
banded at the time of transplanting or broadcast prior
to transplanting and the remainder in 1 to 2 applica-
tions at later times to the side of the hills. Split
applications favor reduced soluble salts buildup in the
root zone and a reduction in the amount of the basic
fertilizer that may be lost from the root zone due to
leaching. Timing and number of split applications
depend upon weather, the grower's experience, and
Starter Solutions-In some sweet potato regions
outside of Florida, starter solutions are added to the
soil around the plants shortly after they are set in the
field. This application can be helpful in getting the
plants established in the field. The solutions consist of
to 6 pounds of a fertilizer such as 10-52-8 in 100
gallonss of water. One-half to one pint of the solution is
appliedd around each plant in the field.
TRANSPLANTING TO THE FIELD
Exact spacing will be determined by available
pment and the grower's preference.
Between rows 31/2 to 5 feet
Between plants 10 to 12 inches
Height of ridges 10 to 14 inches
No. of plants/acre 9,000 to 12,000
some method of cutting the vines is best used p
the digging. With the "middlebuster," the vines c
cut by utilizing two coulter discs placed 18 i.
apart in front of the middlebuster. Care should
exercised to insure that the depth of the discs is
justed so as not to injure or cut the roots. W
utilizing the sweet potato "digger," a slightly differ
approach is often used. The coulter discs are spact
conform with the width of the bed or hill. Follo'
the discs, a flailing-type beater or a spinning I
mower is used to remove most of the foliage and \
from the row. This allows only the roots to be ha"
over the digger, preventing handling problems ca
by excessive accumulation of vines and leaves.
CURING AND STORAGE
Sweet potatoes are marketed as "uncur,
"cured" roots. Most early potatoes are ma
shortly after they are dug without curing or hav
a brief curing period to "set" the skin. "Cured'
most frequently are stored and sold at a late
Curing facilitates the formation of wound-cork
beneath injured areas on the root. Some wot
occurs during the harvesting process regardless
carefully they are handled. However, careful hE
reduces the amount of injury and reduces the
tial for loss due to shriveling, storage'rots, etc.
The curing conditions should be 4 to 7 days
to 850 F. with a relative humidity of 85 to 90 pe
Following proper curing, storage conditions s)
be: 55 to 600 F. and a relative humidity of 85
percent. Storage below 550 should be avoided b
chilling injury may result.
1. Florida Department of Agriculture, Division of Plant I,
"Florida Sweet Potato Weevil Regulations."
2. Florida Extension Circular 193, "Commercial Vegetab
and Disease Control Guide."
3. Florida Extension Circular 196, "Chemical Weed Co
Florida Vegetable Crops."
4. Florida Extension Circular 225, "Commercial Vegef
5. USDA Agriculture Handbook 388, "Sweet Potato C
6. USDA Farmers Bulletin 1059, "Sweet Potato Dise,'
7. USDA Pamphlet 874, "The Sweet Potato Weevil."
Since extension circulars are revised from time to time
to obtain latest editions.
Range of Planting Dates
Area Bedding(') Transplanting(2)
North Florida Jan. 15 to Mar. 15 Mar. 1 to June 1
Central Florida Dec. 15 to Feb. 15 Feb. 1 to June 1
South Florida Nov. 1 to Feb. 1 Dec. 15 to June 1
(1) 40 to 50 days are required to obtain first sets (draws)
when soil temperature is maintained at about 800 F.
(2) For early crop, 120 to 140 days are required from this
date to harvest. For late crop, 150 days or more are
required for highest yields.
Sweet potato roots are bedded in special plantbed
structures or bedded in the field for the production of
plants for transplanting. Hotbeds with electric heat-
ing coils or other means of supplying heat to the soil
can be utilized to advantage where cold temperatures
occur during the bedding operation. Where field bed-
ding is used, plastic can be of some advantage as an
over-the-row ground cover until initial emergence of
the shoots. This type of covering must be removed as
soon as the shoots begin to emerge or "burning" of the
shoots will occur. Where permanent or portable
structures are used, adequate ventilation must be
provided to prevent excessive heat and humidity ac-
cumulation and thus reduce the possibility of
developing serious disease problems.
Vine cuttings can be used from the seedbed or
from fields set out for early production. However,
where cuttings are used, a longer growing season is
required before harvest maturity is reached. In some
instances where soil-borne diseases are troublesome,
cuttings can be used to reduce losses. In this method,
plants that appear to be disease-free are selected and
cuttings are taken from them. The cuttings are then
placed directly into the production field. For the
production of an early crop, the use of "draws" taken
from the seedbeds is preferred. Plants can also be
purchased from various sources, if desired, but care
must be taken to assure that they are certified free of
diseases and insects.
Seed Conditioning-Take seed out of cold
storage and keep in 75 to 80 F. temperatures with
high humidity for 2-3 weeks before planting to
Bed Fertilization-For plants grown in struc-
tures, the fertilizer can be broadcast over the top of
the soil covering the seed roots. One pound of a 4-8-8
fertilizer per bushel of seed can be used and watered
in. The application should be repeated after each
pulling of plants. For plants grown in field beds, the
fertilizer can be broadcast and incorporated prior to
formation of the raised bed. An initial application of
800 to 1,000 pounds per acre of 4-8-8 can be used
followed with a sidedressing of 200 pounds per acre of
4-8-8 after each pulling.
Spacing-When using plantbeds, place seed roots
adjacent to one another but not touching. Six to
seven bushels of seedstock of 1 1/2 inch or larger
diameter will furnish plants for 1 acre in three
pulling. When field bedding, rows 3 1/2 to 4 feet
apart with roots 6 inches apart in the furrow can be
used. Sixty to eighty bushels of seed roots are required
to bed one acre in this manner and this will produce
plants for about 10 to 15 acres in three pulling.
Disease Control-Strict sanitation should be
exercised at all phases of production, handling and
storage. Residue roots, vines, etc., should be removed
from the storage area and the facilities cleaned with
fungicides or chlorine solutions. Select only disease-
free stock for bedding. Rogue bedded roots frequently
to remove diseased plants. Do not use contaminated
soil or irrigate with water that has drained from areas
where sweet potatoes have grown previously.
Fumigate the soil to be used in the bedding operation.
Bedding cloths, crates, etc., can be sources of disease
contamination. Seed treatments can be used, but they
can only act on surface spores and not spores on the
inside of the root.
PRODUCTION FIELD FERTILIZATION
The basic or initial application of fertilizer may be
applied before, during, or shortly after transplanting,
or in split applications combining any two or all there
of these. Supplemental fertilizer may be applie
whenever needed during the growing season and es
pecially after heavy, leaching rains.
Soil pH and Minor Elements-Optimum p]
range for sweet potato production is between 5.5 anc
6.0. Minor elements may be needed on certain soil
especially those with pH of 6.0 or above.
The use of trade names in this publication is solely for the
purpose of providing specific information. It is not a
guarantee or warranty of the products named and does not
signify that they are recommended to the exclusion of others
of suitable composition.
Prepared by: Stephen R. Kostewicz and James Montelaro with
cooperation with other personnel of the Institute of Food and
Agricultural Sciences. Special assistance was given by Mr. J. E.
Brogdon, Dr. D. W. Dickson, Dr. R. S. Mullin and Dr. W. L.
This public document was promulgated at an an-
nual cost of $393.96, or 3.94 cents per copy to inform
potato growers how to grow sweet potatoes.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30,1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
Joe N. Busby, Dean