• TABLE OF CONTENTS
HIDE
 Front Cover
 Table of Contents
 Introduction
 Plant characteristics
 Seed
 Hybrids
 Cultural requirements
 Nutritional requirements
 Land preparation and planting
 Weed control
 Insects and their control
 Diseases and their control
 Nematodes and their control
 Use of pesticides
 Physiological disorders
 Harvesting and marketing














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 714
Title: Sweet corn production on the organic and sandy soils of Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00027231/00001
 Material Information
Title: Sweet corn production on the organic and sandy soils of Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 48 p. : ill. (some col.) 23 cm. ;
Language: English
Creator: Guzman, V. L ( Victor Lionel ), 1914-
University of Florida -- Agricultural Experiment Station
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1967
 Subjects
Subject: Sweet corn -- Florida   ( lcsh )
Sweet corn -- Soils -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: V.L. Guzman ... et al..
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027231
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 001595656
oclc - 01310906
notis - AHL9751

Table of Contents
    Front Cover
        Page 1
    Table of Contents
        Page 2
    Introduction
        Page 3
    Plant characteristics
        Page 3
        Page 4
    Seed
        Page 5
    Hybrids
        Page 6
        Page 7
        Page 8
        Page 9
    Cultural requirements
        Page 10
        Page 11
    Nutritional requirements
        Page 12
    Land preparation and planting
        Page 13
        Page 14
        Page 15
    Weed control
        Page 16
        Page 17
        Page 18
    Insects and their control
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
    Diseases and their control
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
    Nematodes and their control
        Page 35
        Page 36
    Use of pesticides
        Page 37
        Page 38
    Physiological disorders
        Page 39
        Page 40
        Page 41
    Harvesting and marketing
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
Full Text
4 February, 1967


SWEET CORN PRODUCTION ON THE
ORGANIC AND SANDY

SOILS OF FLORIDA


HiU.E LIBRARY

I APR 7 1967

I r '.. U.i'iv. of Florid3
1'- ---- ----


Iricultural Experiment Stations
R. Beckenbach, Director


Institute of Food and Agricultural Sciences
University of Florida, Gainesville








CONTENTS


Page

Introduction .. .... 3

Plant Characteristics -. ......- 3

Seed .. ............ -------- 5

Hybrids .. ... 6

Cultural Requirements ..- --- -- 10

Nutritional Requirements 12

Land Preparation and Planting ..... 13

Weed Control .. 16

Insects and Their Control --.... 19

A General Insect Control Program ... 20

Specific Insects and Their Control ........ 23

Diseases and Their Control -. 28

Nematodes and Their Control 35

Use of Pesticides .. 37

Physiological Disorders 39

Harvesting and Marketing 42







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, nor does it signify that they are approved to the exclusion
of others of suitable composition.







SWEET CORN PRODUCTION

On the Organic and Sandy Soils of South Florida

V. L. Guzman
H. W. Burdine
W. T. Forsee, Jr.
E. D. Harris, Jr.
AUTHORS J. R. Orsenigo
R. K. Showalter
C. Wehlburg
J. A. Winchester
E. A. Wolf

INTRODUCTION
Sweet corn, a mutant from field corn, was well known by the
American Indians before the discovery of this continent. The
kernels have a high sugar content at fresh market maturity.
The plants in general are smaller than field corn varieties and
more susceptible to disease and insect damage.
Sweet corn was a minor crop in Florida prior to 1946. It is
estimated that fewer than 100 acres were grown annually before
this time. Field corn was grown more extensively than sweet
corn for fresh use, probably because of its greater resistance
to pests. A great expansion in sweet corn production was attained
during the fifties after the introduction of DDT for insect con-
trol. New hybrids, better methods of culture and harvesting,
and more efficient pesticides have increased average yields from
120 crates per acre in 1946 to 190 in 1962. Acreage reached an
all-time high in 1962-63 with 54,200 acres valued at $18 million.
Approximately 75% of Florida's sweet corn is grown in Palm
Beach County, chiefly on the organic soils of the Everglades.

PLANT CHARACTERISTICS
Sweet corn, Zea mays var. rugosa Linnaeus, is a member of
the grass family. Rugosa means wrinkled, referring to the ap-
pearance of the kernels when dry. The wrinkled crystalline or
Guzman: Horticulturist, Everglades Station, Belle Glade
Burdine: Associate Soils Chemist, Everglades Station
Forsee: Chemist and Head, Everglades Station
Harris: former Associate Entomologist, Everglades Station
Orsenigo: Associate Horticulturist, Everglades Station
Showalter: Horticulturist, Food Science Department, Gainesville
Wehlburg: former Associate Plant Pathologist, Everglades Station
Winchester: Assistant Nematologist, Everglades Station
Wolf: Horticulturist, Everglades Station
3







SWEET CORN PRODUCTION

On the Organic and Sandy Soils of South Florida

V. L. Guzman
H. W. Burdine
W. T. Forsee, Jr.
E. D. Harris, Jr.
AUTHORS J. R. Orsenigo
R. K. Showalter
C. Wehlburg
J. A. Winchester
E. A. Wolf

INTRODUCTION
Sweet corn, a mutant from field corn, was well known by the
American Indians before the discovery of this continent. The
kernels have a high sugar content at fresh market maturity.
The plants in general are smaller than field corn varieties and
more susceptible to disease and insect damage.
Sweet corn was a minor crop in Florida prior to 1946. It is
estimated that fewer than 100 acres were grown annually before
this time. Field corn was grown more extensively than sweet
corn for fresh use, probably because of its greater resistance
to pests. A great expansion in sweet corn production was attained
during the fifties after the introduction of DDT for insect con-
trol. New hybrids, better methods of culture and harvesting,
and more efficient pesticides have increased average yields from
120 crates per acre in 1946 to 190 in 1962. Acreage reached an
all-time high in 1962-63 with 54,200 acres valued at $18 million.
Approximately 75% of Florida's sweet corn is grown in Palm
Beach County, chiefly on the organic soils of the Everglades.

PLANT CHARACTERISTICS
Sweet corn, Zea mays var. rugosa Linnaeus, is a member of
the grass family. Rugosa means wrinkled, referring to the ap-
pearance of the kernels when dry. The wrinkled crystalline or
Guzman: Horticulturist, Everglades Station, Belle Glade
Burdine: Associate Soils Chemist, Everglades Station
Forsee: Chemist and Head, Everglades Station
Harris: former Associate Entomologist, Everglades Station
Orsenigo: Associate Horticulturist, Everglades Station
Showalter: Horticulturist, Food Science Department, Gainesville
Wehlburg: former Associate Plant Pathologist, Everglades Station
Winchester: Assistant Nematologist, Everglades Station
Wolf: Horticulturist, Everglades Station
3







translucent kernels are less bulky when dried than those of the
starchy types of field corn.
When a corn seed germinates, it sends up a single shoot,
and the primary root grows down from the first node. The tem-
porary primary root is replaced by permanent roots from the
second to the seventh node. These penetrate the soil to a distance
of 4 feet or more in all directions. Since the greatest root con-
centration is within 2 feet around the plant, sweet corn is
considered a relatively shallow-rooted crop. Brace roots appear
at about the time of tasseling.
In young corn, sheaths of the older leaves encircle the
younger leaves. As the plants grow taller, the leaves become
separated. There is one leaf for each node, and the number of
leaves in a plant varies from 7 to 13, always in odd numbers.
The plant terminates in a tassel, which is the male flower. The
female flowers develop at the base of a node on a shank. Leaves
develop at the nodes of this shank. The leaf sheaths are husks
encircling the ear, and the blades of these leaves, if present,
are called flags. The cob is the receptacle bearing the ovaries,
the future kernels, and the styles or silks. The kernels are ar-
ranged in pairs of rows. The older kernels are those at the base
of the cob. In multiple-eared varieties, the upper ear is usually
more advanced in maturity than the lower.
Development of the sweet corn plant can be divided into three
periods, each of approximately 20 to 30 days. The first is form-
ative, in which all structures are formed or differentiated.
The second is growth, when all structures reach full size; and
the third is reproductive. Because of early differentiation of the
plant's parts and the peculiar anatomical structures, there is
practically no provision for recovery from injury by the roots
and stems after they are established. However, damage to roots
is less severe than similar damage to the tops of the plants.
Effect on yields from pruning of roots or light damage to the
leaves is less injurious at early stages, increasing considerably
to tasseling time and decreasing progressively from silking to
market maturity.
There are a number of hereditary factors or genes which
determine the sugar content of the kernel. The sugar of sweet
corn is due to the recessive gene su. Immediately after reaching
optimum fresh maturity, sugar in the kernels begins to turn into
starch by enzymatic action. Respiration also consumes sugar
for living processes. Loss of sugar is slowed by low temperatures,
but sugar content of the kernels diminishes continuously with







time. One gene discovered relatively recently, the shrunken
2 (sh2) gene present in so-called supersweett" corn, conditions
the production of twice or more the amount of sugar found in
regular sweet corn containing the su gene, and the sugar is
retained much longer after harvest. Presence of this factor may
be very desirable in corn shipped to distant markets, since the
high sugar content is retained for long periods after harvest.
Considerable progress has been made in incorporating this gene
into standard sweet varieties. A hybrid, Illinichief Super-Sweet,
containing this factor is commercially available, but its ears
will not make Fancy grade.

SEED
With the trend to plant to final stand without thinning, seed
soundness is of utmost importance. The corn kernel contains a
sub-miniature corn plant with most of its structures already
present. Within the seed this embryonic plant is alive and
functions accordingly, but since it is enclosed in a restricted
environment, by-products of the life processes accumulate in
toxic amounts, causing a progressive loss in vitality and ger-
mination, and ultimately death. This process, also called degen-
eration, usually starts when maturity of the ear of the parent
plant is completed. Thus, any seed is at some stage of degen-
eration. The important point is the degree of degeneration at
the time of planting. Degeneration is accelerated by two main
factors: 1) high moisture content of the seed during storage
and 2) high storage temperature. For longest life, sweet corn
seed should be stored at 6 to 8% moisture in sealed, aluminized
polyester or similar containers and at temperatures just above
freezing. Moisture of the seed during storage is apparently more
important than temperature, but also more difficult to control
if containers are not adequate. A seed with low moisture con-
tent absorbs water from a moist atmosphere and deteriorates
rapidly. Weak seed produces poor stands and greater variation
in emergence, plant size, ear maturity, and yields.
Sweet corn seed is classified for size within flat and round
types: medium flat, large flat, etc. Type has little or no effect
on germination. Wider variation in germination occurs in seed
of the same type which are poorly graded, kept in different
storage conditions, or differ in age. Large seed produces more
uniform stand and maturity and the greatest yields. This is
especially true under adverse conditions for germination. Small
seed produces more barren stalks than large seed does.
5







HYBRIDS
Table 1 gives the characteristics of the main hybrids when
grown during the spring in organic soils.
Iobelle.-This highly productive, midseason hybrid, also
known as Florida 104, is well adapted to most conditions and
is recommended for late fall, winter, and spring harvest. The
plants, are quite susceptible to leaf blight. Ears have good husk
coverage and medium to dark green flag leaves, but their husk
color is light green. Appearance of the ears is good. They have
14 to 16 rows of bright pale yellow kernels, and, in most cases,
are well filled to the tips. Eating quality is fairly good, and
the quantity of kernel pericarp is less than in most other hybrids
commonly used in the area.
Florigold 106 and 106A.-These two highly productive hy-
brids, recommended for late fall, winter, and spring harvest,
are related and in general have similar characteristics. Both
are more resistant to leaf blight than lobelle. The ears mature
approximately one day earlier than lobelle and have small to
medium dark green flags and husk. The ears are cylindrical with


Figure I.-Typical ears of lobelle or Florida 104 and Wintergreen. Husk
cover and size of flags of these hybrids are preferred by the trade.
6







14 to 16 rows of medium sized yellow kernels and are well
filled to the tips. Eating quality is only fair and husk cover is
poor, resulting in green tips under some conditions.
Florigold 107.-Recommended for late fall, winter, and spring
harvest, but most adapted for spring production. This highly
productive yellow hybrid matures three days earlier than lobelle.
The plants have medium resistance to leaf blight. The ears
have medium to poor husk covers, and under some conditions
they may have green tips. However, husk coverage is, in
general, slightly better than that of Florigold 106. Flags are
small to medium, and husks and flags are dark green. The 14-
row ears are attractive, cylindrical, and well filled to the tips,
but of only fair eating quality.
Silver Queen.-This white hybrid, recommended for late fall,
winter, and spring harvest, matures one day later than lobelle.
The plants are quite susceptible to leaf blight. Husk cover over
the ear tips is good, and the medium length flags are dark green.
The ears are cylindrical, slightly longer than lobelle, with 14
rows of kernels well filled to the tips. Appearance of the ears is
good, and eating quality is excellent. The ears remain in good


Figure 2.-Typical ears of Florigold 106 and 107 hybrids.
7








Table 1. Average characteristics of sweet corn hybrids grown in organic soil from February to May, 1963 to 1965. Belle Glade, Florida.



0 0 P go P o

belle Yellow 85 6.6 6 3.3 1.9 7.5 1.72 0.3 16 4.0



Florigold 106 Yellow 84 6.4 7 2.8 1.7 7.9 1.69 0.1 16 2.3








00 loberigold 106Ale Yellow 84 6.4 11 3.1 1.8 7.8 1.7266 0.1 16 2.8




Florigold 107 Yellow 82 6.6 13 4.1 1.8 7.7 1.68 0.1 14 2.5

Wintergreen Yellow 82 5.8 5 3.0 1.5 7.8 1.66 0.3 14 2.0

Illinichief Yellow 87 6.3 14 4.5 2.0 7.9 1.81 1.2 16 4.0
Super-Sweet


1/ Number of kernel rows on ear reported as majority number
2/ Zero=no blight lesions to Five=severe lesions.







marketable condition
longer than most of
the yellow hybrids,
but the kernels tend to
become broad. Pollen
from yellow varieties
falling on the recep-
tive silks of white va-
rieties will cause the
formation of yellow
kernels. Plantings of
this variety, therefore,
must be isolated by a
minimum distance of
1/4 mile or by at least
20 days difference in
S. planting dates.

Wintergreen.-Sug-
gested for early spring
harvest trials, this
vigorous hybrid, more
resistant to leaf blight
than Florigold 106,
produces marketable
ears three days earli-
Figure 3.-Ears of Silver Queen at optimum. er than lobelle. The
At this stage the sugar content is very high and
the pericarp very tender. The ears have excellent plants have very few
eating quality. suckers, and are about
a foot shorter than
those of Iobelle, though slightly taller than those of Florigold
106. The ears, slightly smaller in diameter than lobelle, have a
majority of 14 rows of medium size yellow kernels. The ears are
well covered with dark green husks and medium to long dark
green flags.
Illinichief Super-Sweet.-This hybrid, carrying the sugar
retention factor, matures 2 days later than Iobelle, and is sug-
gested only for small spring harvest trials. The plants are quite
susceptible to leaf blight and insect damage. It must be isolated
from all other corn by distance or planting dates to insure
freedom from cross pollination. Foreign pollen falling upon the
silks of this hybrid will produce starchy or field corn kernels
9







on the resulting ear. Ears are larger than those of Iobelle and
have 14 to 16 rows of medium size yellow kernels which do
not generally cover the ear tips. It has medium to poor husk
cover and medium size dark green flags. The ears grade below
U. S. Fancy, because the ears have green tips and the unfilled
ear tip is over 1 inch under adverse conditions. Appearance of
the ear is fair, and its eating quality is good, although the
kernels are slightly tough and watery. The kernels dent very
slowly, retain their high sugar content, and remain in good
eating condition for an extended period. It has been pre-pack-
aged experimentally with good consumer acceptance. The seed,
because of low starch content in the collapsed endosperm, ger-
minates poorly in cool or excessively moist soils. To insure
satisfactory stands, it must be shallow planted, drilled rather
heavily, and thinned to 8 to 9 inch spacing.

CULTURAL REQUIREMENTS
Climate.-Sweet corn is a warm-season crop. Its growth and
productivity are greatly affected by temperature, water supply,
and atmospheric moisture. Germination is impaired by tem-
peratures below 50F. Growth rate increases with a rise in
temperature up to 89 F and decreases above this point. Tem-
perature influences the number of days required to reach
maturity. A variety planted in late summer may need 60 days
to reach the harvest stage; the same variety planted in late fall
may need almost twice as long to reach the same stage. It ap-
pears that low night temperatures strongly affect growth rate
of the plant. During the winter in south Florida, day tempera-
tures most of the time reach the 70's, whereas night tempera-
tures may remain below 50 F for many days. This, associated
with dry prevailing winds, short days, and cloudy conditions,
could reduce size of the plants and delay maturity considerably.
Chilling of the plants, especially during the seedling stage, pro-
duces transverse pale striping of the leaves. Freezing tempera-
tures kill the plants.
Soil and Moisture Requirements.-Sweet corn grows satis-
factorily in most soils of south Florida, provided adequate
nutrients are available. Light-colored sandy soils are less suited
to sweet corn than those containing more organic matter, ap-
parently because of poor water-holding capacity. In these lighter
colored soils overhead irrigation may be necessary to secure
good stand and uniform plant size. Sweet corn grown on these







sandy soils is more susceptible to dryback or shriveling of the
ears and poorly filled tips than on the darker sandy soils. Virgin
organic soil is less satisfactory for sweet corn production, especi-
ally during the summer, than soil farmed for several years. In
virgin organic soil, plant size is uneven, and under certain cli-
matic conditions barren stalks, shriveled ears, and green ear
tips develop. This may be partly due to improper fertilizer
distribution, particularly of micronutrients, to excessive nitro-
gen, high temperatures, periodic water shortage, or to unknown
causes.
In general, low soil moisture tends to promote root growth
more than top growth and vice versa. Therefore, a few days
after germination the water table should be lowered. At the end
of the "growth" period the water table could be raised, especially
in sandy soils during the late spring to avoid disorders in the
ears caused by a temporary water deficit. Water deficiency during
the reproductive period may cause cessation of growth of the
ear's husk, but not of the cob; as a result, the ear may grow
out of the husk and have a green tip which results in a cull ear.
In sandy soils water is kept as high as possible in the lateral
ditches during germination. A few days after germination, the
water is lowered to maintain an 18 to 20-inch water table in
the field. In organic soil, water is usually sufficient for ger-
mination. After emergence of the corn plants the water is
lowered in the lateral ditches to about 30 inches.
Good drainage, particularly in the root zone, is very important
in preventing root injury. In sandy soils the lateral irrigation-
drainage ditches are spaced about 120 feet center to center.
Shallow ditches are dug approximately 200 feet apart across
the rows after planting to discharge surface water rapidly. In
organic soil, drainage is effected through mole-drains to the
lateral ditches connected to the pumping station. Mole-drains
should be renewed each season to insure efficient drainage and
irrigation.
Dry winds increase evaporation. During time of water stress
this could result in green tips, dryback, and poorly formed ears.
Strong dry winds during pollen-shed may cause blanking or
missing kernels in the ear. These factors, acting singly or in-
teracting with each other and with nutritive and parasitic
conditions, can substantially influence yields.







NUTRITIONAL REQUIREMENTS
Good yields of corn with desired quality depend largely on
the fertilizer program, including amount, formula, and time of
application. Efficient fertilizer utilization depends upon soil-
water relationships, which must be optimum throughout the
entire growing period. Analysis of a representative soil sample
is the best method of ascertaining nutritional requirements of
the crop.
Sandy Soils.-Sweet corn grows well in sandy soils with a
pH range of 5.5 to 7.0. Acid sands limed to pH values of 5.5
to 5.7 have produced earlier maturing corn with larger and
better filled ears than unlimed soils. Good yields of high quality
corn can be obtained on soils with pH values above 7.0 pro-
vided manganese deficiencies are prevented by nutritional sprays.
Sands requiring lime should be treated well in advance of seed-
ing with a liming material such as high calcic or dolomitic lime,
or basic slag. Hydrated lime may be used on palmetto and
other highly acid areas where rapid action is imperative. Other-
wise, the less soluble sources are recommended to prevent
over-liming.
In sandy soils a minimum of 160 pounds N, 100 pounds
P205, and 120 pounds K20 are required for optimum yields of
high quality ears. After heavy rains as much as 60 pounds of
additional nitrogen and potash may be needed. Nitrogen increases
number and weight of U. S. Fancy ears and length of the ear.
Potash appears to have a similar but less pronounced effect.
The most efficient method is to apply all the phosphate at
planting along with some nitrogen and potash. The remaining
nitrogen and potash should be supplied in two or more side-
dressings, the last at the time of the final cultivation. Fertilizer
applied at planting should contain 25 to 30% organic nitrogen,
and 0.3, 0.5, 0.3, 0.2, and 2.0% CuO, MnO, ZnO, B203, and MgO,
respectively, to prevent deficiencies of these elements. Thus,
1,000 pounds of 4-12-6 fertilizer banded 3 inches to either side
and 2 inches below the seed, followed by two side-dressings of
12-0-6, each at 500 pounds per acre, should supply the approxi-
mate amount necessary for high yields of good quality ears.
If leaching rains occur, two to three applications of 200 pounds
10-0-10 per acre should be top-dressed between rows.
Sprays containing manganese, zinc, and iron neutral salts, at
2 to 4 pounds in 100 gallons of water per acre, are beneficial
where such elements are deficient. Under some conditions, the
12







sulfates of manganese and zinc may cause leaf burn; therefore,
the oxides or carbamate fungicides containing these two ele-
ments should be used.
Black plastic mulch is used occasionally on raised beds con-
taining sufficient fertilizer for one or two crops with some
degree of success. There are problems, however, with this cul-
tural method which will require considerable research before
recommendations can be made.
Organic Soils.-Special consideration must be given to fer-
tilizing virgin peat soils. Many crop failures have resulted from
improper incorporation of copper, zinc, and boron compounds,
and potash into the total volume occupied by the root systems
of corn plants. The following general recommendation is made
for virgin peat soils. Immediately after the first plowing and
disking, broadcast 500 pounds per acre of 0-6-30 containing 3.0%
CuO. Plow this under and refit the land for seeding. Just prior
to seeding, broadcast and disk in 1000 pounds of 0-6-30 per acre
containing 1.5, 1.0, 0.5, and 0.4% CuO, MnO, ZnO, and B203,
respectively. At seeding, apply in bands 500 pounds of 0-15-5
per acre including 1.0% MnO if the soil pH is 6.0 or higher.
Peat and muck soils that have been cropped for two years
or more should require no additional copper fertilization. Fer-
tilizer recommendations of potash and phosphate for previously
cropped soils can be made only on the basis of soil tests. As
a general practice it is always best to broadcast most of the
required potash fertilizer and apply most of the required phos-
phate in bands 3 inches from the drill and 1 inch deeper than
the seed. Never use as band applications for sweet corn fertili-
zers with a higher potash analysis than 8% or at rates higher
than 800 pounds per acre.
No yield response to nitrogen has been obtained on sweet
corn growing in organic soils. Thus, nitrogen need not be applied
to these soils except under prolonged cold and rainy conditions
when quick tissue tests show a scarcity of nitrogen in the plants.

LAND PREPARATION AND PLANTING
A good seedbed is important for uniform germination and
efficient cultivation, weed control, and harvesting. Since all south
Florida land is flat, seedbed preparation is simplified to proper
plowing, disking, and leveling. If a cover crop has been planted
or weeds have been allowed to grow during the summer or if
the corn follows another crop, the green matter should be plowed
13







under well in advance. Since water is supplied by sub-irrigation,
fields should be level. Depressions in the field cause uneven
growth of the plants due to variations in water or to excessive
accumulation of rainfall. The use of raised beds is practical
only where the sub-soil is shallow and impervious or where
plastic mulch has proved to be desirable.
Sweet corn production is geared for continuous harvest;
plantings start in August and end in April. The bulk of the crop
is harvested in the spring with smaller production during the
fall and still smaller during the winter. Most of the winter crop
is grown in protected areas-on organic soil near Lake Okeecho-
bee, or on sandy soils near the coast. The planting schedule
should be adjusted, taking into consideration that corn seeded
in August tends to mature 10 or more days earlier than normal
(spring planting) and that the harvest interval becomes shorter
than the planting interval. Plantings in the fall for winter har-
vest mature 10 or more days later than normal, and the harvest
interval is longer than the planting interval. Plantings of a
midseason hybrid in late winter and early spring tend to mature
in about the normal time of 78 days, but the harvest interval
becomes shorter than the planting interval as the season pro-
gresses from cool to warm. Thus, a hybrid will require approx-
imately 65 days to reach maturity when seeded in August, 110
days when seeded in November, 85 days when seeded in January,
and 75 days when seeded in February.
Other considerations in establishing planting schedules are
hybrid differences and the fact that corn remains in good mar-
ketable condition longer during cool weather than during warm
weather. Day length, cloudiness, and other conditions affect
the growth of sweet corn, but the main climatic factor is tem-
perature.
Multiple row planters with 4 or 8 rows per unit are used to
drill sweet corn. In organic soils sweet corn is commonly planted
in the bottom of a shallow furrow, but it can be planted on a
flat seedbed if desired. In sandy soil it is planted flat, in a
slightly raised ridge or in raised beds with or without plastic
mulch. There is no advantage in planting deeper than 1 inch
except in light sandy soils where lack of moisture in the upper
1 inch could limit germination. The permanent roots of the corn
plant tend to grow at a fixed depth from the soil surface re-
gardless of planting depth. Shallow planting appears to improve
yields, especially under adverse weather conditions. Large seed
shallowly planted produce the most vigorous plants.
14







Most sweet corn seed is drilled in 36-inch rows. Plant
spacing in the row varies from 10 to 16 inches. For the highest
yields of ears with good appearance, it is necessary to plant
in 28 to 32-inch rows with plants spaced 8 to 10 inches in
the row to give an approximate stand of 24,000 plants per acre.
Ear size and appearance are improved slightly at wider row
and plant spacing, but the number of marketable ears is re-
duced correspondingly.
Two methods for approaching the desired plant spacing may
be followed. One is to seed twice the required amount of seed
(16 to 18 pounds per acre) and later thin to stand, and the
other is to seed to final stand. The first method is adapted to
the Cole Planter No. 11, although it can be used with any pre-
cision planter capable of seeding about 4 inches apart in the
row. The John Deere precision planter 495A is commonly used
for planting to final stand, but the gear arrangement must be
modified to reduce the effect of slippage and the drive speed
reduced materially. The better method is to plant thickly and
remove excess plants later. The extra seed and expense of
thinning are compensated for by extra profit. Neither the Cole
nor the John Deere planter gives the desired plant spacing, but
the nearest approximation is to seed heavily and thin when the
plants are 6 to 8 inches tall. With the Cole this is accomplished
by using a 32-pocket soybean plate with the number 12 gear,
and driving at 2 mph. The pockets of the plate should be filed to
accommodate the round or flat sweet corn kernels. The same
effect can be accomplished with the John Deere, by planting two
kernels in hills properly spaced and later thinning to one plant.
The main disadvantage of thinning is the great amount of labor
needed. As labor is increasingly more difficult to obtain, planting
to final stand is becoming the common practice. Best results are
gained by careful planting and good management. Seed should
be of high germination and vitality and carefully graded for size.
After selecting the proper plates and gears, run a test with speed
and type of soil intended to be used and make corrections if
necessary after germination. Plant at a rate of 3.5 mph or
slower, and finally, protect the plants by effective control of
birds, rodents, weeds, diseases, insects, and mechanical damage
when cultivating or spraying.
Hill planting with two or more plants per hill gives lower
yields than comparable drilled plant populations. Uneven ma-
turity and ears with longer unfilled tips also result from hill
planting.







All recommended hybrids respond similarly to row and plant
spacing and season. Therefore, there is no need to change row
or plant spacing during the various growing seasons.


WEED CONTROL
Sweet corn weed control programs start with repeated,
timely tillage during the off-season to reduce weed populations.
Weeds in the crop are usually controlled mechanically, although
chemical weed control is also effective. Cultivation equipment
and methods vary with culture-whether corn is planted on
raised beds or in leveled fields. Cultivation equipment for raised
beds usually weeds only one bed per pass. Tools cultivating
two or more rows are used for flat culture. Sweep, rolling, or
rotary tools can be used most effectively when weeds are small
and the soil surface is dry. Two to four cultivations may be
necessary, depending on soil preparation and seedbed condition
at time of planting, numbers of grass and broadleaf weed seed
present, and the season. Deep cultivation, which destroys many
feeder roots near the surface, must be avoided.
It is usually desirable to throw some soil to the base of the
young corn plants for support at maturity, especially if high
winds are likely during the latter part of the growing period.
Working soil to the plants can be done during the last cultiva-
tion when the corn is laid by, when 15 to 20 inches tall; or
a small amount of soil can be worked to the row at each cul-
tivation. The latter method will probably destroy fewer roots
and provide better weed control. Cultivation should be shallow
after corn roots extend across the rows.
Herbicides may also be used to control weeds in sweet corn.
Herbicide benefits include: 1) prevention of weed and grass
competition during crop emergence and early growth; 2)
avoidance of possible injury due to cultivation; and 3) reduc-
tion in numbers of weeds that interfere with harvesting. Her-
bicides are applied either preemergence, before corn or weed
seedlings come up, or postemergence to kill small weeds in the
growing crop. The choice of chemical treatment may be in-
fluenced by cultural practices, especially layby hilling, which
moves soil to the base of the plant for increased support. The
period from planting to layby is generally about 4 weeks. Pre-
emergence chemicals should be applied immediately after plant-
ing. Good soil moisture improves weed control. Preemergence
herbicides have enhanced corn stem weevil control programs.
16


































Figure 4.--Chemical weed control in the row from pre-emergence band-
applied DNBP at 12 pounds per acre on organic soil.


Figure 5.-Chemical weed control in the row from pre-emergence band-
applied atrazine at 3 pounds per acre on organic soil. The photograph was taken
two weeks after application when the middles would be cultivated in commercial
practice.








Table 2. Herbicides for sweet corn weed control.


Chemical


CDAA (Randox)

CDEC (Vegadex)


CDAA + CDEC



o atrazine (Atrazine)


simazine (Simazine)


DNBP (Premerge or
Sinox PE)


atrazine



2,4-D amine salt


Time of Appli-
cation to Crop


preemergence

preemergence


preemergence



preemergence


preemergence


preemergence



postemergence



postemergence


Pounds
Active Ingredient/Acre
Sandy soils Muck soils


Remarks


up to 4 up to 4 Suggested for trial use. More effective against grasses
than broadleaf weeds.

up to 6 up to 6 Recommended. More effective against broadleaf weeds
than grasses.

up to 6 up to 6 Recommended. Combine these for mixed weed populations.
The total amount of active ingredients in the mixture
should not exceed the amount given for each separately.

1 to 2 Recommended. Adequate surface moisture necessary for
best results.

1 to 2 Recommended. Adequate surface moisture necessary for
best results.

3 to 6 6 to 9 Suggested for trial use. Caution-young seedlings may
be injured if heavy rains occur before seedlings emerge
and become established.

1/2 to 1 1/2 to 1 Suggested for trial use. Apply directionally to base of
corn plant. Controls weed seedlings up to 1 inch tall and
also provides some residual control.

/3 to 1/3 to 3/4 Recommended. Apply directionally to base of corn plant.
Varieties differ in tolerance. Use with caution in sensi-
tive crop areas.







Postemergence layby treatments are useful when severe weed
infestations are likely to follow hilling.
Table 2, adapted from Florida Extension Circular 196B, pre-
sents suggested and recommended chemical weed control meth-
ods for sweet corn. Growers who lack experience with herbicides
are urged to make their initial applications to small acreages
for familiarization.
Herbicides may be applied as dry granules or in water as
sprays. Applicators for granules may be mounted on the planter,
and some have divided hoppers so that herbicides and insecti-
cides may be distributed simultaneously. Applicators are avail-
able for full broadcast coverage or for band application only
to the crop row.
Herbicide sprayers are distinct from those commonly used
to apply fungicides and insecticides. Herbicide sprayers utilize
low pressures-25 to 40 psi-and low volumes-20 to 40 gpa-
with flat-fan herbicide nozzles adjusted to provide uniform soil
coverage. Herbicides are applied most effectively when the spray-
er is mounted on the planter. Chemical cost may be reduced by
applying herbicides in bands over the crop row, but effective,
accurate tillage of row middles is required. Weedy soil must not
be moved onto the treated band. Usually, side-shielded rotary til-
lers are most successful in between-row weed control when her-
bicides are banded.
All equipment should be properly calibrated and repeatedly
checked for accuracy. Successful performance will not be real-
ized if the correct amount of chemical is not applied in the
right way at the right time. Calibration methods are available
in Extension Circular 275A or from your county agent.

INSECTS AND THEIR CONTROL
Insect control on sweet corn is closely associated with other
cultural practices. In general, those sound cultural practices
which result in thrifty growth and optimum yields also result
in plants that are better able to withstand and outgrow insect
damage. Many of these cultural practices also result in fewer
insect pests.
Weather conditions affect insect pest populations and the
ability of sweet corn plants to withstand or outgrow insect
damage. There are usually more budworms and earworms on
corn from May to September than in cooler weather. Because
weather conditions become progressively less favorable for crop







growth with the advancing season, fall planted sweet corn is
usually less able to tolerate insect damage than that grown
during the spring. Sweet corn is less able to withstand damage by
insects such as wireworms and the corn stem weevil when the
soil moisture is either too low or too high.

A General Insect Control Program
Certain insect pests usually can be expected on any sweet
corn crop in south Florida and routine control measures should
be applied. Measures to control these primary pests will usually
control other insects that are only sporadically important on
sweet corn.
Insect control on sweet corn can be divided into four pro-
grams: 1) the pre-planting program or those measures taken
before planting; 2) the corn stem weevil control program from
seedling emergence until the plants are approximately three
weeks old; 3) the budworm control program from the cessation
of the corn stem weevil control program until silks appear;
4) the earworm control program from silking until shortly
before harvest.
The Preplanting Program.-This program should be started
as early as possible. The longer the field and surrounding area
has been free of vegetation, especially grass-type vegetation,
the greater will be the insect control. Crop residues should be
plowed under as soon as possible after harvest or abandonment.
Flooding for two weeks or longer should reduce populations
of wireworms and other insect pests, especially if the flooding
period extends into September or until shortly before planting.
Parathion at 5 pounds, or diazinon at 4 pounds of actual
toxicant per acre on organic soils, or either insecticide at 2
pounds on mineral soils should be sprayed broadcast to the
soil surface and immediately disked in to a depth of 6 inches
or more for soil insect control. This treatment should be applied
two or more weeks before planting. Moist soil and a high water
table preceding, during, and immediately after application will
enhance control. Rolling reduces vaporization of the insecticide
from the soil and may result in better control. Parathion at 3
pounds or diazinon at 2 pounds of actual toxicant per acre on
organic soils or either insecticide at 1 pound on mineral soils
can be applied in the seed furrow during the planting operation
as a substitute for the pre-planting broadcast application.
Corn Stem Weevil Control.-Corn stem weevil damage seems
to occur less frequently and less severely on mineral soils than







on organic soils. If the sweet corn grower on mineral soil has
not experienced troubles with this insect, he may go directly to
a budworm control program.
Pre-emergence chemical weed control with cultivation sub-
sequently delayed until after the final corn stem weevil control
spray will result in more effective corn stem weevil control.
Sprays should be applied twice weekly from the day or day
after seedlings emerge for a total of six or seven applications.
Each spray should contain 1 gallon of DDT 2E, or 1 gallon
of DDT 2E plus 1 pint of toxaphene 8E, or 2 quarts of DDT
2E plus 1 pint of toxaphene 8E per 100 gallons. The addition
of toxaphene slightly increases the level of control. One gallon
of DDT 2E is more effective than 2 quarts of DDT 2E in the
DDT-toxaphene combination but results in more emulsifiable
concentrate being applied to the young plants and more like-
lihood of spray damage. DDT 50% WP is far less likely to
cause spray damage, but it is not nearly as effective as the DDT
2E. Eight pounds of DDT 50% WP plus 8 ounces of Triton X-100
is nearly as effective as 1 gallon of DDT 2E.
Sprays can be applied at 50 gallons per acre using two nozzles
over each row until the plants begin to form a canopy over the
soil. Then a nozzle should be added to each side of the row to
apply 100 gallons per acre. Spray should be directed to the lower
stem and adjacent soil.
Budworm Control.-Budworms are controlled more easily
than corn stem weevils; therefore, the concentration of sprays
and usually the frequency of application can be reduced when
the plants are about three weeks old.
Budworm control sprays should contain 2 quarts of DDT 2E,
21/ pint of parathion 4E or 111/ pints of toxaphene 8E per 100
gallons. Parathion 15%' WP at 2 pounds of toxaphene 40 '
WP at 4 pounds per 100 gallons can be substituted for the
emulsifiable concentrates. DDT 50% WP is not nearly so effective
as the emulsifiable concentrate and should be used at 4 pounds
per 100 gallons with 8 ounces of Triton X-100.
The addition of 1/ pint of parathion 4E or 3/ pint of tox-
aphene 8E to 2 quarts of DDT 2E per 100 gallons has resulted
in better budworm control than any of the above insecticides.
Budworm control sprays should be applied weekly during
most of the season. If control is not adequate, they should be
applied twice weekly. They should first be applied at 100 gallons
per acre with two nozzles above the row, and a single nozzle
at either side of it. As the corn grows taller, an additional
21












































Figure 6.-Budworm damage


to sweet corn.


nozzle should be added to each side of the row to increase ap-
plication to 150 gallons per acre. Spray must be directed into
the whorl of the corn plants.
A budworm spray should be applied when the tassels fully
emerge from the whorls, because budworms at this time mi-
grate to the ears.
At tasseling, the field should be closely checked for corn silk
flies. This insect, and its damage and control, are described on
page 27.
22







Earworm Control.-Insecticides should be applied when the
first silks appear and continued until all silks have dried. From
October through March, applications should be made every
other day. During the rest of the year, they must be made
daily. Adequate control becomes progressively more difficult as
summer approaches. Control is especially difficult in late May,
June, and thereafter.
Insecticides may be applied as dusts or sprays. Dusts are
especially suitable for aerial applications. In ground applications,
dusts or sprays should be directed at the silks.
Dusts containing 10% DDT, 10% Sevin, 2% parathion, or
5% DDT plus 1% parathion should be applied at 35 to 40 pounds
per acre. In sprays, DDT 2E at 4 quarts, Sevin 50% WP at 4
pounds or Sevin 80% sprayable at 2.5 pounds per acre should
be applied in 50 gallons of spray per acre. Parathion should not
be applied within three days of harvest.

Specific Insects and Their Control
Wireworms.-Wireworms feed on the seeds as well as the
underground portion of the corn seedling. They usually bore
into the corn stem just above the crown to cause reduced growth







. .. -













Figure 7.-Earworm damage to sweet corn.
23















F]
7
/f


1I
a


Figure 8.-Wireworms attacking a sweet corn seedling.
or wilt and often the eventual death of the plant. Two species
of wireworms, the corn wireworm, Melanotus communis
(Gyllenhal), and the southern potato wireworm, Conoderus
falli Lane, damage sweet corn in south Florida.
Wireworm eggs are laid in the soil, especially soil that con-
tains grasses or grass-like plants. The wireworms are usually
already present when the corn is planted. The corn wireworm







is a long, slender, tube-shaped, hard-bodied yellow or orange
grub that grows to be about 112 inches long. The southern
potato wireworm is softer-bodied, wider relative to its length,
white to cream-colored, and attains a length of about 1 inch.
With each species, the mouth parts point straight ahead and
can be seen from above the grub. Control measures are given
on page 20.
The Banded Cucumber Beetle.-The beetles, Diabrotica bal-
teata LeConte, chew upon sweet corn leaves and lay their eggs
in the soil at the base of the plant. Grubs hatch from these eggs
and bore into the underground portion of the plant. The banded
cucumber beetle is approximately 1/ inch long, is green with four
yellow bands across the back, and has a reddish brown head.
The grub is approximately 1/ inch long when mature and is
white, dirty white, or cream-colored. It has a brown head and a
dark plate on its back at the extreme rear.
The pre-planting parathion or diazinon soil treatment for
wireworm control plus the sprays for corn stem weevil or bud-
worm control usually control this insect.
Cutworms.-The black cutworm, Agrotis ipsilon (Hufnagle),
and the granulate cutworm, Feltia subterranean (Fabricius),
are grayish to black caterpillars that come up from the soil
at night to cut off young plants near the soil surface or chew
large holes in the base of larger plants. The caterpillars can
be found in the upper inch or two of soil near freshly cut off
plants.
Usually, the sprays applied for budworm or corn stem weevil
control will control cutworms. However, if a heavy infestation
of cutworms is known to exist, 2 pounds per acre of actual
toxaphene, TDE, or chlordane should be applied as a spray or
dust before planting, and the soil should not be disturbed for
3 to 5 days. A 2.5% toxaphene or 2% chlordane bait can be
used as above at 20 to 40 pounds per acre. If cutworm damage
to young sweet corn plants is noticed, a bait should be applied
at once. Cutworm treatments should be made in the evening.
The Lesser Cornstalk Borer.-Damage by the lesser corn-
stalk borer, Elasmopalpus lignosellus (Zeller), is similar to wire-
worm damage. A greenish-blue caterpillar with darker reddish
bands bores into the stalk from a soil-covered silken web at the
soil surface. It is sometimes within the stalk and sometimes
within the silken web. This caterpillar, which attains a length
of approximately 3/ inch, wiggles rapidly when disturbed.
The lesser cornstalk borer is a sporadic pest. Several years
25







often pass with no reported damage. Therefore, routine pre-
ventive measures hardly seem justified. However, the following
can be done if lesser cornstalk borers are thought to be present.
Three pounds of parathion 15% WP or 2 quarts per acre of
either aldrin 2E or heptachlor 2E can be applied in a spray
that contains a wetting agent or detergent to help wet the soil
and webbing. The first application should be made, covering
the rows and the middles, just before the crop emerges. The
second application should be made as soon as the crop emerges
and before cultivation, using 3 pounds of parathion 15% WP
or 1 quart of aldrin 2E or heptachlor 2E per acre. Higher gal-
lonages (up to 300 per acre) of dilute coarse sprays at about
100 pounds pressure are more effective.
The Corn Stem Weevil.-This insect, Hyperodes humilis
(Gyllenhal), appears to be a greater pest on the organic soils of
the Everglades than elsewhere. Treatments may not be necessary
on mineral soils.
The eggs, which are cylindrical with hemispherical ends,
are embedded in the coleoptile or lower leaf sheath of the young
corn plant. They are about 1/32 inch long and about one-third
that in diameter. They are creamy white when first laid but
change to a dark brown in a day or two.
The grub is white, legless, and has a light brown head. It
is about 1/32 inch long when first hatched and grows until it
is about 1/4 inch long. The grubs tunnel randomly in the lower
stem of the corn plants. Damaged plants may wilt and then
die, be stunted, or break over in heavy winds. Control measures
are given on page 20.
Budworms.-The fall armyworm, Spodoptera frugiperda (J.
E. Smith), and the corn earworm, Heliothis zea (Boddie), are
caterpillars that feed within the bud or whorl of the sweet
corn plant.
The fall armyworm moth lays its cream-colored eggs in flat
clusters that are covered with waxy strands, usually on the
underside of the leaf. Ridged yellowish eggs of the corn ear-
worm are laid singly. The young caterpillars first eat holes in
the underside of the leaf, bud, then migrate into the whorl.bud.
The fall armyworm has a wide dark stripe down each side
plus other stripes. It may be green, pinkish, light tan, or nearly
black. However, most of those individuals found in sweet corn
whorls are green with black stripes. This caterpillar grows to
a length of about 11/2 inches. The inverted white "Y" on the
26







dark brown or nearly black head of the fall armyworm distin-
guishes it from the corn earworm.
Corn earworms may be yellow, light green, pink, brown, or
nearly black. There are alternating light and dark stripes run-
ning the length of the body. The head is yellow and unspotted.
The corn earworm is about 2 inches long when full grown. Bud-
worm control measures are discussed on page 21.
The Corn-Silk Fly.--The corn-silk fly, Euxesta stigmatias
Loew., is green, about 14 inch long, and has clear wings with
distinct black bands. It restlessly runs up and down leaves,
stalks, and corn ears with its wings often moving like scissors
blades. It lays tiny elongated eggs in the ear tips. Maggots that
hatch from these eggs cause a soggy brown ooze about the
kernels.
This insect has been relatively unimportant in recent years,
and it should be controlled where parathion is used in the bud-
worm control program. However, the grower should closely
examine each planting after the tassels begin to emerge but
before any silks are present. If flies are seen, a spray containing
/2 pint of parathion 4E per 100 gallons should be applied. Ad-
ditional applications should be made if the field is reinfested
with flies.
Aphids.-The most common species on sweet corn is the corn
leaf aphid, Rhopalosiphum maidis (Fitch). These small yellow
to green insects have a pair of tubules extending from the rear
of their body. They suck plant juices from the tassels, silks, or
the ear husks. Infested ears become sticky, and a black mold
grows on them. Aphids are usually not a problem where an
emulsifiable concentrate is used in the spray program. If aphids
are present, apply 1/2 pint of parathion 4E or 1 pint of Phosdrin
2E per 100 gallons as a spray, parathion as a 1 or 2% dust, or
Phosdrin as a 11/2 dust. Parathion should not be applied within
3 days of harvest; Phosdrin should not be applied within a
day of harvest.
Silk Feeding Beetle.-The bumble flower beetle, Euphoria
inda Linnaeus, and other beetles that look like June beetles
infrequently eat the silks. Missing kernels may result. As these
beetles often develop in accumulated decaying organic matter,
the sweet corn field and surrounding areas should be kept free
of piles of plant material. Sprays that contain 1 to 2 pounds of
actual Sevin per 100 gallons should be effective when applied to
the ears.
Earworms.-The fall armyworm and the corn earworm at-
27







tack sweet corn as earworms. Both were described under bud-
worms. There are two sources of earworms. When the tassel
unfolds, budworms migrate to the newly developing ear. The
other source of earworms is eggs that are laid on or near fresh
silks. Although they may sometimes eat through the husk to
attack the side of the ear, most earworms feed on the silks and
enter through the silk channel to attack the tip of the ear. The
earworm population may be almost completely composed of corn
earworms or of fall armyworms, or of a mixture of the two
species.
The spray program for earworm control has been discussed
on page 23.
Scavenger Beetles and Fruit Flies.-These insects do not
normally enter the sweet corn ear until it has been damaged
by another insect, birds, or by some other means. The most
frequent scavenger beetle, Carpophilus sp., found within sweet
corn ears is small and brown, and has wings that are far shorter
than its body. Fruit flies, Drosophila spp., are the very small
flies often seen around decaying or overripe fruit.


DISEASES AND THEIR CONTROL

Weather conditions more than any other factor determine
the disease incidence; humid weather, even heavy dew, favors
the appearance and spread of diseases caused by fungi and
bacteria.
Northern Leaf Blight.-This disease, caused by the fungus
Helminthosporium turcicum Passerini, is considered to be the
most important one affecting sweet corn in southern Florida. It
appears in late fall or early winter and from this time on may
be present until the end of the crop season. The corn plants
may become infected at the age of six weeks or later; very
young plants seldom show symptoms of the disease. Northern
leaf blight is favored by relatively cool temperatures ranging
from 650 to 800F. However, when the weekly mean temperature
is below 60 F. or when the mean relative humidity is lower
than 60%, the disease is checked. Losses may range from very
light to as much as 80% of the yield, depending on severity
of the attack and the time when the disease appears. If heavy
infection occurs before silking, it can cause severe damage;
whereas if the disease becomes established when the ears are
already formed, only minor damage results.
28








- ----.1i~~ ih


Figure 9.-Northern leaf blight lesions on sweet corn leaves.


The characteristic symptoms are large spindle-shaped dead
spots on the leaf blade, up to 1, inch wide and 4 inches long.
They begin as small, round or oval yellow spots which enlarge
in the direction of the leaf blade, turn grayish-green, and appear
water-soaked. The affected tissue dies, and the lesions become
straw-colored or tan. Several lesions may merge to produce large
areas of dead tissue, especially toward the leaf tip. In damp
weather the fungus produces large numbers of spores which
may spread to other parts of the plants to produce new infec-
tions. Generally the lower leaves show more and larger lesions;
as the disease progresses, more spots also appear on the higher
leaves, further reducing the area of green leaf tissue. Severely
affected fields have a dry and scorched appearance.
There are a number of fungicides, among them maneb, nabam
plus zinc sulfate, and zineb, that give good control under con-
ditions of low and moderate disease incidence. It is almost
impossible to prevent the corn plants from becoming seriously
affected, if temperature and rainfall are favorable to the devel-
opment of the disease.
Frequency of fungicide application varies with weather con-
ditions. Weekly sprays generally are sufficient during fall and






winter, as long as the mean temperature is in the low sixties.
In spring, with higher temperatures, the frequency of applica-
tions should be increased, especially if rain and dew keep the
plants wet during the night and for several hours during the day.
Since rains may wash off the protective film of fungicide, an
extra treatment is recommended as soon as possible after a heavy
rain. The addition of a good sticker may help in preventing the
fungicide from being washed off by rain.
Fungicide applications should continue until about 10 days
before harvest. A minimum of 150 to 200 gallons of spray per
acre is necessary to cover the leaves of full grown corn; young
plants need proportionally less spray. It has been determined
that the use of two overhead nozzles is superior to one, and that
150 gallons of spray per acre are adequate under moderate
disease conditions, but 250 gallons may be necessary under
severe conditions. Old plants should be plowed under as soon
as possible after harvesting to prevent fungus spores on these
plants from infecting nearby fields. For the same reason it is
better to avoid successive corn crops on the same land.
Southern Leaf Blight.-This disease is caused by Helmintho-
sporium maydis Nisikado and Miyake. It is favored by warm,
moist weather and is generally found in early fall and again
in late spring. During part of the growing season the symptoms
of both Helminthosporium diseases may be found on the same
leaf.
Southern leaf blight is less common than Northern leaf
blight, and losses from this disease usually are not severe.
However, susceptible varieties of sweet corn have been known
to suffer severely from this disease during rainy periods in
early fall.
The lesions caused by H. maydis are easily distinguished
from those produced by H. turcicum. They are much smaller,
with more or less parallel sides and a lighter, almost creamy-
white color. The spots may be up to 1 inch long and 14 inch
wide, but generally they are not much longer than their width.
Sometimes several spots may unite to form larger areas of
dead tissue. As is the case with Northern leaf blight, the lesions
appear on the lower leaves first. Under conditions of tempera-
ture and moisture favorable for the development of the disease,
even the highest leaves gradually become covered with spots.
The same measures used against Northern leaf blight con-
trol Southern leaf blight. If the weather is dry in early fall,
the spraying may be postponed until the first symptoms appear.




































Figure 10.-Rust pustules on both sides of sweet corn leaves.


Thereafter, weekly spraying with maneb, nabam plus zinc sul-
fate, or zineb usually keeps the disease in check.
Rust.-Rust is caused by the fungus Puccinia sorghi
Schweinitz. It can be recognized by the small, round or elon-
gated yellow or light-brown spots, approximately 1 16 inch
in diameter, that are scattered over both surfaces on the leaf.
These spots become rust-brown with age. When the leaf tissue
ruptures, the powdery masses of spores are liberated. The
disease is of minor importance, and no special control measures
are necessary, as the fungicides recommended for leaf blights
usually are adequate to control rust.
Seedling Diseases.-During cold weather, when germination
of the corn seed and subsequent growth of the seedling are
retarded, the roots and lower part of the shoots are often at-
tacked by soil fungi. Infected plants show one or more sunken
31
































Figure 11.-Bacterial leaf blight lesions on sweet corn. This disease is
characterized by clearly marked linear lesions.


Figure 12.-Bacterial stripe lesions on sweet corn leaves.

32








V1~~
I'i


Y


\


W '1
Figure 13.-Basal ear rot of sweet corn. Under favorable conditions the
bacterial leaf blight will affect corn stems and shank, causing rot of the lower
part of the ear.







brown lesions on the shoot close to the seed, while the leaves
are often wilted and grayish-green. In extreme cases damping-
off may occur. If weather conditions improve, the affected plants
may partially recover, but they will be stunted.
During cool wet weather it is usually Pythium that causes
this seedling blight, while Rhizoctonia is more common under
warmer, drier conditions.
Treatment of the seed with a fungicide prior to planting pro-
tects the seed from being invaded by soil-borne pathogens, but
is not a guarantee against infection of the seedlings under
adverse growing conditions.
Bacterial Leaf Blight.- This disease, caused by the bacter-
ium Pseudomonas alboprecipitans Rosen, is characterized by
sharply delineated dead spots and stripes on the leaves from 1/2
to several inches long and about 1/16 inch wide. As the affected
area becomes older, the tissue dies and turns straw-colored
to creamy-white. Several lesions may merge and form broad
bands of dead leaf tissue. The dead tissue of the stripes splits
easily in windy weather and gives the leaf a shredded appear-
ance. The symptoms can be found on both the lower and higher
leaves. Generally this disease is of minor importance, although
shredding of the affected leaves and ensuing withering cause
some damage. During prolonged periods of high humidity, the
disease can also affect the corn stalk and lower part of the ears.
In mild cases a brown, water-soaked spot on the leaf sheath
or on the outside husk of the ear is the only symptom. Under
conditions favorable for the development of the disease, a severe
rot of stalks and ears may occur. Stalks often break at the
affected part.
Bacterial Stripe.-Bacterial stripe, caused by Pseudomonas
andropogonis (E. F. Smith) Stapp, usually affects only the
lower leaves of the corn plant. The symptoms are irregular
blotches and stripes, often merging and forming large areas
of affected tissue. In the beginning the stripes are olive-green,
water-soaked, and somewhat translucent. As the tissue dies,
color of the affected areas progressively turns yellow, orange,
and finally bright tan. Damage is usually negligible, although
the affected leaves may die prematurely. As soon as dry weather
occurs, the newly formed leaves remain healthy and the plant
recovers. However, under prolonged humid conditions, young
corn may occasionally suffer severely. No practical control
measures for either of the above mentioned bacterial diseases
are known.







NEMATODES AND THEIR CONTROL
Unlike diseases and insects, nematodes usually do not cause
easily recognized symptoms. Frequently nematodes are not
suspected to be causing crop damage until efforts to control
it through nutritional and pesticidal treatments have failed.
It is necessary to have soil and root samples examined to be
sure that nematodes are present, but visual observation of a
plant and its roots can often indicate if they are a problem.
Nematode injury usually results in irregularly shaped areas of
stunted plants in the field. Plants may be chlorotic and may wilt
during hot weather even when soil moisture is considered ade-
quate for crop production. Nematodes may cause short, stubby,
or galled roots which may also have brown or colorless lesions.
Sting Nematodes.-Sting nematodes, Beloniolaimts spp.,
are serious pests of sweet corn in sandy soils but rarely in or-
ganic soils. Their feeding may give the root system the appear-
ance of having been cut off 5 or 6 inches below the soil surface.
Colorless lesions which may turn brown with age are caused
near the root tips.
Stubby Root Nematodes.-These nematodes, Trichodorus
spp., are important pests of sweet corn on sandy soil and may
cause severe stunting of the plants. The roots are very stubby
because the nematodes apparently interrupt cell division and
normal root growth, and the root tip becomes slightly swollen.
Frequently populations of this nematode increase rapidly after
soil fumigation. The population may be greater six weeks after
treatment than before treatment. Reasons for this are not clear,
but observations suggest that excessive rates of fumigant
should be avoided-use no more than the recommended rate.
Root Knot Nematodes.-While root knot nematodes,
Meliodogyne spp., are known pests of vegetable crops, they are
usually not recognized as pests of sweet corn. They may cause
severe stunting of sweet corn and small galls on the roots near
the tips. These often break off if the plants are not removed
carefully from the soil.
Lance Nematodes.-These nematodes, Hoplolaimus spp., are
often found in crop land but are rarely considered to be damag-
ing to sweet corn. If the population is high before the land is
cleared for planting, a nematicidal application may increase the
crop yield.
Spiral and Meadow Nematodes.-Spiral nematodes, Helicoty-
lenchus spp., and root lesion or meadow nematodes, Pratylen-
35







chus spp., may severely stunt sweet corn, causing brown lesions
along the roots.
Several methods of nematode control are available. The cost
of the treatments (which varies greatly) as well as other fac-
tors, including the time needed for treatment and the effect of
the treatment on the soil, must be considered.
Flooding.-This is a common method of controlling root knot
nematodes, and it usually is as effective as nematicide treat-
ments. Laboratory investigations have shown that an alternate
flooding-drying program is superior to constant flooding. Two
weeks of flooding, two weeks of drying, and two additional
weeks of flooding were equal to seven months of constant flood-
ing. The drying period should be increased if moderate to heavy
rains occur. Cultivation during the drying period may increase
its effectiveness.
Clean Fallow Cultivation.-While this is a common practice,
it is not recommended because of its detrimental effect on the
sand and muck soil. Sandy soil maintained in a fallow condition
for a long period and then planted to a crop erodes badly during
high winds and heavy rains, exposing the crop roots and damag-
ing the foliage. Fallowing is generally done during the summer
months with periodic cultivation for weed control. Six to eight
weeks of clean fallow cultivation is the minimum time for
effective nematode control under optimum conditions.
Rotation.-If root knot nematodes are the only plant nem-
atodes in the soil, rotation of sweet corn with pangolagrass
should give very good control. A year of pangolagrass should
give sufficient control for three years of corn production. While
rotation with pangolagrass gives good control of all plant nem-
atodes for tomato production, its effect on corn is not completely
known. Pangolagrass must be maintained relatively weed-free
for best results.
Cover Crops.-Crotolaria spectabilis and hairy indigo will
give control of root knot nematodes and will add organic matter
and nitrogen to the soil. Crotolaria is apparently the more effec-
tive of these two crops, but its seeds are toxic to livestock
and poultry; therefore it must be grown in areas where it will
not be a hazard or it must be disked under before seed are pro-
duced.
Chemical Control.-This is usually the most satisfactory
method of nematode control. A variety of nematicidal chemicals
are available, some of which control only nematodes while others
control weeds, insects, and soil-borne diseases as well as nema-
36







todes. These vary in cost, and only a few are economical enough
for sweet corn production. Those recommended for sweet corn
nematode control are listed below.
Gals./Acre Applied'
Nematicide Sand Muck
Dichloropropene 20-25 30-40
Dichloropropene Dichloropropane 20-25 30-40
Ethylene dibromide W-85 41/2-6 9
These three nematicides are toxic to plants and must be
applied from 1 to 3 weeks before planting so that the chemicals
can escape from the soil. They escape very slowly when the
soil is wet or when the soil temperature is about 60 degrees.
Under these conditions a longer waiting period is necessary.
The escape of the chemicals may be accelerated by a single disk-
ing about a week after treatment. These chemicals are most
easily used as broadcast treatments applied with applicator
chisels spaced 8 inches apart and 8 inches deep. A heavy drag,
or roller, to compact the soil after application will improve the
effectiveness of the treatments.
Follow the label recommendation carefully and do not get
either of these chemicals on your clothes or shoes. They can
cause serious burns.

USE OF PESTICIDES
Pesticide Residue.-Sweet corn that has a pesticide residue
greater than the tolerance established under the Federal Food,
Drug and Cosmetic Act cannot be shipped across state lines.
Before applying any pesticide, read the label to make sure
that the pesticide is labeled for that use. See that forbidden pest-
icides do not drift to sweet corn when treating other crops.
Conversely, pesticides should not drift from sweet corn to crops
for which they are not labeled. Follow recommendations, espe-
cially those relating to dosage and minimum days from the final
application to harvest.
Pesticides must be applied correctly. The spray program
should be well planned and closely supervised. Discussed below
are several factors important in effective pest control.
The Right Pesticide in the Right Amount.-See that the
correct amount of pesticide is correctly measured for the amount
of water in the spray tank. Pesticide powders should be accu-
If applied only in a band the rates will be reduced a corresponding
amount.







rately weighed and not thrown into the tank by the bucket or
canful. When practical, obtain pesticides in relatively small
packages so that one or more packages can be emptied into
the spray tank to give the desired dosage.
Use High Quality Pesticide Formulations.-Poor quality for-
mulations cause poor pest control, plant damage, or undue wear
on equipment.
Emulsifiable concentrates should contain no sediment. In gen-
eral, emulsifiable concentrates that contain xylene or xylene-
range aromatic petroleum as the solvent are less likely to damage
plants.
Wettable powders and dusts should be finely ground with no
grit or lumps and of uniform color and texture.
Pesticide Mixtures.-To save time and expense of additional
applications the grower naturally wants to apply pesticide mix-
tures. Usually, this is fairly safe with the materials recom-
mended for sweet corn pest control. But some materials may
be incompatible when mixed and cause: 1) improper dispersal
of the materials within the spray tank, i. e., materials settling
out at the bottom or rising to the top of the tank or the presence
of curds or globules; 2) decreased control of one or more of the
pests or diseases; or 3) plant damage.
Before trying new combinations of pesticides, mix the mater-
ials in about a pint of water and at the concentrations to be
used. The material should mix readily in the water with only
mild shaking, and a sediment should not form rapidly when
shaking is discontinued. There should be no curds, globules, or
pronounced change in color. Use new combinations initially on
only a few plants, and observe the plant and pest response for
a few days before treating large acreages. Even though the
same active ingredients are used, be alert for incompatibilities
if you change brands of any of the pesticides.
When nabam and zinc sulfate are used in spray mixtures,
they should be added to the tank before the other materials.
Spraying Pressure.-The spraying pressure need only be
great enough to get a good pattern from the nozzle and should
not exceed 200 psi. The spray should come from the nozzle as
droplets-there should be NO fog. Excessive spraying pressure
causes drift, poor coverage, and undue wear on the spraying
equipment. Dosage can more effectively and more economically
be increased by going slower, or by using larger or more nozzles.
Weather.-Insecticides should not be applied when the wind
is high or strong enough to cause drift. Sprays can be applied







under more windy conditions than dusts. Dusts are more effec-
tive if applied in the late evening or early morning when there
is no wind and the plants are moist with dew. If possible, sprays
that contain emulsifiable concentrates should be applied when
the weather is favorable for rapid evaporation.
Speed and Boom Bounce.-The sprayer speed should not be
greater than 5 mph. Also, the spray alleys should be kept as
smooth as possible. Only a small rise, dip, or turn of the sprayer
wheel can cause a tremendous movement at the end of the
boom. This boom bounce is more pronounced and lasts longer
at higher speeds and with longer booms. A nozzle aimed at
the sky or digging into the soil does not put much pesticide on
the plant.
The grower should not overplant to the extent that he lacks
the time and equipment for proper control of sweet corn pests.
Warning.-Pesticides are POISON-they can KILL-handle
them with care and follow these safety precautions.
1) READ AND HEED ALL THE SAFETY PRECAU-
TIONS ON THE LABEL.
2) Store pesticides in a dry and LOCKED location. Only
authorized and responsible persons should have access
to pesticides.
3) Keep pesticides in their original containers and keep
these tightly closed. NEVER transfer any pesticide to
an unlabeled container.
4) Dispose of ALL containers so that they cannot be con-
tacted by humans or animals.
5) Do not let pesticide sprays or dust drift into inhabited
areas or upon materials that may be dangerously con-
taminated.
6) See that supervisors and all persons who contact pes-
ticides know the symptoms of poisoning. If poisoning is
suspected, immediately take the victim to a physician.
Tell the physician of every pesticide that may have
been contacted.

PHYSIOLOGICAL DISORDERS
Dryback or Shrivel.-This condition is the shriveling of the
kernels just before market maturity. Depending on severity of
the disorder, the extent of shriveling may be from a few kernels
near the tip to more than three-fourths of the ear. Shrivel is
more severe on the second or lower ear than on the primary or
39





























Figure 14.-Dryback or shrivel is exhibited on the two lower ears extending
downward from the apex, about 25 and 35% of the total length of the ear.

top ear in hybrids that tend to bear two ears. Of the hybrids
which have been grown here commercially, Silver Liner and
Golden Security have shown this tendency, most commonly fol-
lowing heavy rains in May and early June.
According to research in California, an adequate supply of
nitrogen at the tassel stage greatly reduces shrivel even at the
close spacing of 8 inches between plants. Work with field corn
has shown that nitrogen needs of the corn plant are greatest
from two weeks before tasseling until three weeks after tassel-
ing, reaching a maximum at silking time.
Large differences among hybrids for tendency to shrivel have
been exhibited in screening trials of experimental hybrids. This
indicates genetically controlled differences for uptake of nutri-
ents, a deficiency of which results in the disorder.
Tipblanking or Unfilled Tip.-This condition also seriously
detracts from the appearance of fresh market corn and is con-
sidered a serious fault. It is characterized by full kernel develop-
ment from the base of the ear to a certain point, followed
by rudimentary or undeveloped kernels on the apical end of the
ear. It is found separately and in conjunction with dryback. Un-
der unfavorable conditions most hybrids may exhibit the disorder


* t-~ ~ .~ _. ,\. ~lr) CI. re





























Figure 15.-Unfilled tips of varying severity of three ears of a sweet corn
hybrid.

to some extent. Potassium deficiencies have been reported to
result in unfilled tip characterized by an unfilled tapering cob.
Work with field corn indicates that although the growing corn
plant continuously accumulates potassium until the denting
stage, its maximum requirement is reached three weeks after
silking, or at about the time fresh market sweet corn would be
harvested.
Field observations in south Florida also indicate that reserve
carbohydrate supply may be a major factor. Plants that have
had a sizeable portion of their foliage destroyed by leaf blights
display an excessive amount of unfilled tip. Corn maturing dur-
ing the cooler temperatures in the winter and early spring
months displays more unfilled tip. Hybrids that tend to mature
two ears show more unfilled tip on the secondary or lower ear
than on the primary or top ear.
Nodal Browning or Nodal Darkening.-This phenomenon is
frequently seen in sweet corn hybrids growing in south Florida.
Whether it is a cause or a result of factors that affect plant vigor,
and consequently limit yield and quality, is not clear. It is char-
acterized by a darkening of the nodal inside tissue of the stem,
41







most severe at the base and gradually diminishing in intensity
towards the top. There are large differences between hybrids
that are commercially grown or have been grown in the area.
Hybrids exhibiting the most severe expressions are probably
Golden Security and R-8. Hybrids showing an intermediate ex-
pression are lobelle and Winter Garden, while Florigold 106
and 107 show least browning. Other hybrids have not been
observed under comparative conditions. Corn with poor root de-
velopment growing in wet compact soil following heavy rains
shows most severe symptoms. Slow growing plants in the winter
season seem more inclined to exhibit this tendency. Work with
field corn showed that the dark tissue at the nodes contained
deposits of aluminum and/or iron. Differences between plants in
open-pollinated corn varieties were observed. Later work in-
dicated that inbred selection for hybrid corn production resulted
in differences between inbreds developed from the same open
pollinated varieties. Further work has indicated that excessive
iron deposits in the nodal tissue may be a symptom of potassium
deficiency.

HARVESTING AND MARKETING
Harvesting.-Sweet corn quality on the consumer's table
depends upon quality at harvest and handling after harvest.
Eating quality at harvest is governed by season, inherent
characteristics of the hybrid, and its maturity. Grade and appear-
ance are determined by the hybrid and its maturity, production
practices, and seasonal weather conditions. When harvested at
optimum maturity, the kernels are plump, sweet, succulent, and
tender. If harvesting is delayed, the eating quality deteriorates,
because sugar and moisture content decrease and starch and
pericarp (seed coat) content increase. Typical yellow varieties
harvested at different maturities have a range of 2 2 to 4%
sugar, 64 to 84% moisture, and 1 to 2% pericarp. A white hy-
brid, Silver Queen, has a range of 21/ to 611%o sugar when
harvested at different maturities. Field temperatures and in-
herent hybrid differences affect the number of days that ears
remain at optimum maturity.
Two methods of harvesting are used. 1) Tra -dawn
wagons or trailers move through the fields and transport the
hand-pulled or machine-pulled ears to an assembly area in the
field or to a nearby shed, where the corn is graded and packed
The new mechanical harvesters cut the stalks near the grounii,
remove the ears, and convey them to a bin attached to the
42






-~p


Figure 16.-Two newly built fresh market sweet corn harvesters. These
machines harvest two rows and convey the ears to a bin attached to the harvester
(top-Ellis harvester) or to an independent wagon (bottom-Boots and Hooks
harvester).



























Figure 17.-Grading and packing sweet corn at an assembly area in the
field being harvested.

harvester or to an independent tractor-drawn trailer, which in
turn carries the corn to the assembly area. 2) Self-propelled
packing houses (mule trains) move through the fields, and the
hand-pulled ears are placed on conveyors for sorting, grading,
and packing by workers on the harvester. With both methods,
the fields are harvested only once, and ears with wide ranges
of maturity and size must be sorted before packingO Packed
crates are transported from the field to the precooler by truck.)
Grading.-United States Standards for Green Corn provide
for three grades: U. S. Fancy, U. S. No. 1, U. S. No. 2. Factors
considered in grading include cob length, kernel filling, dryback,
maturity, injury from insects, diseases, bird damage, husk char-
acteristics, and number of ears per crate. Florida sweet corn is
graded and sold as U. S. Fancy or a percentage of U. S. Fancy.
The U. S. Fancy grade requires a minimum of 6 inches in cob
length with 75% of its length filled with kernels. Ear length
varies among hybrids, growing seasons, and cultural methods.
Packing and Containers.-Sweet corn at an assembly area in
the field or on a self-propelled harvester is packed as one or two
grades: U. S. Fancy or a percentage of U. S. Fancy. When two
grades are packed, the larger, more mature ears are packed 41/,
to 5 dozen ears per crate, and the smaller, less mature ears are




























Figure 18.-Grading and packing sweet corn in a self propelled packing
house, or mule train, traveling through the field.

packed 5 to 61/2 dozen per crate. Florida sweet corn is packed
in at least seven sizes of wirebound crates. The principal sizes
measure approximately 9 x 11 x 22 inches and 9 x 12 x 22 inches.
Since the demand is greater for units of 5 dozen ears, several
sizes of crates are used to provide the capacities for 5 dozen
ears of varying sizes.
In the 41/2 to 5 dozen packs, the ears are placed in 5 layers
with the tips reversed in alternate layers. In most instances,
only 10 or 11 ears per layer can be placed crosswise in the crate.
Six ears are often placed lengthwise along the sides of the crate.
The crate was designed for no protruding ear tips and shanks.
Improper closure of wirebound crates results when number and
size of the ears exceed the crate capacity. If the crate is bulge-
packed and if any of the four wires are securing it improperly,
ears and crate are subject to mechanical damage.
Trimming.-The trade prefers long ears and shanks and a
full husk with numerous flag leaves. When ears are harvested,
shanks are often 5 to 6 inches long. But the presence of long
shanks and flags are detrimental to the quality of the harvested
ear. Shelf life of the kernels after harvest can be extended by
trimming off the flags and part of the shanks. Husk freshness
45







is maintained by water taken from the kernels. Removal of part
of the husk and shank before packing also greatly reduces ship-
ping space requirements.
Prepackaging.-Sweet corn is one of the most difficult com-
modities to prepackage at production levels because of the
constant need for moisture and refrigeration. If more than the
outer husk is removed, the kernels must be protected from dehy-
dration. In preparing sweet corn for consumer packing or retail
display, varying amounts of husk are removed. Thirty to 44
percent of the total ear weight consists of husk. Completely
husked ears in film-wrapped packages have been delivered from
Florida to distant markets, and arrived in good condition when
adequately refrigerated. Recent test shipments from Belle Glade,
Florida, to New York were successful when the ears were trim-
med to 8-inch lengths, 50', of the husks were removed with a
full-length window of exposed kernels, -and the ears were sprin-
kled with water, packed 5 ears per tray, overwrapped with
shrink film, packed 24 packages per master container, and vacu-
um cooled to 400F.
Quality Control.-Much of the sweet corn grown in Florida
exceeds the U. S. Fancy standard. Florida's harvesting, pre-
cooling, and shipping practices have placed sweet corn on many
distant markets with an appearance far superior to locally grown
corn. However, the eating quality is not always superior, because
this is more difficult to maintain than appearance factors. Pre-
cooling is essential to reduce the rate of conversion of sugar to
starch and to prevent increased kernel toughness. Without ade-
quate precooling (40F. cob temperature), over half of the
sugars may be lost during the first 18 hours following harvest.
After packing, the crates of corn should be transported to the
precooler without delay. Considerable quality deterioration oc-
curs on the precooler platform if the corn is not promptly pre-
cooled. Even though the crates are shaded from the sun, ear
temperatures increase rapidly because of respiration.
Precooling Methods.-Most sweet corn is hydrocooled in
large mechanically refrigerated units or smaller units using
ice. Crated corn moves through the hydrocooler beneath a shower
of 31 to 34 F. water. Crates remain in the larger units about
30 minutes and in the smaller units for only 10 minutes. The
period of time in the hydrocooler and the rate of water circula-
tion influence the corn temperature much more than slight dif-
ferences in water temperature. Cob temperatures average about
60F. after hydrocooling instead of the recommended 40.



















,Nj


Figure 19.-Top icing a carload of sweet corn before shipment. The ice will
reduce ear temperature and supply water for maintaining freshness during transit.
Increasing quantities of sweet corn are being vacuum cooled
to about 40"F. during a 30-minute period in a large sealed tube.
Rapid precooling results from the evaporation of 19 moisture


T\-







for each 10 degree decrease in temperature when the air pres-
sure is reduced by a pump or steam jet. The corn must be wet
before vacuum cooling to compensate for the loss from evapora-
tion and to prevent later denting of kernels.
Lowering the temperature of crated corn by hydrocooling is
slow because of poor accessibility of cold water to the ear due
to the husk and the crate. Husked ears can be hydrocooled in one-
half the time required for ears in the husk, and individual ears
can be cooled faster than ears in containers. Vacuum cooling is
rapid, since the ears in husks, crates, or film-wrapped consumer
packages are very accessible to the cooling effects.
Top Icing.-As soon as the corn is precooled, it is loaded
into refrigerated trucks or rail cars for shipment. Adequate top
ice continues to reduce ear temperatures during transit. Melt-
ing ice also provides a constant supply of water, which is
essential for maintaining husk freshness.
Quality at Consumer Level.-Growers, shippers, and all mar-
keting agencies should do their utmost to maintain good eating
quality after harvest. Succulence is maintained fairly well to the
retail store, and the ears in the store can be adequately protected
from dehydration by icing or packaging. Tenderness of the ker-
nels (pericarp content) does not change if temperatures are
maintained at 40F. or lower. Sugars slowly change to starch
in ordinary sweet corn hybrids when stored at 400F., but the
loss of sugars is very rapid at higher temperatures. More ade-
quate precooling and shortening the marketing period will pro-
vide distant consumers with more "sweet" in Florida corn.








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