• TABLE OF CONTENTS
HIDE
 Front Cover
 Credits
 Table of Contents
 Introduction
 History
 Botanical relationships
 Uses
 Flower structure and sex varia...
 Climate and soil
 Propagation
 Planting
 Fertilization
 Mulching and irrigating
 Thinning of fruit
 Picking, packing and shipping
 Yields and returns
 Developing new varieties and seed...
 Diseases
 Insects
 Literature cited














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 350
Title: Papaya culture in Florida
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027244/00001
 Material Information
Title: Papaya culture in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 35 p. : ill. ; 23 cm.
Language: English
Creator: Wolfe, Herbert S ( Herbert Snow )
Lynch, S. J ( S. John )
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1940
 Subjects
Subject: Papaya -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 34-35.
Statement of Responsibility: H.S. Wolfe and S.J. Lynch.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027244
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000924581
oclc - 18218065
notis - AEN5208

Table of Contents
    Front Cover
        Page 1
    Credits
        Page 2
    Table of Contents
        Page 3
    Introduction
        Page 3
    History
        Page 3
        Page 4
    Botanical relationships
        Page 5
    Uses
        Page 6
    Flower structure and sex variations
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
    Climate and soil
        Page 17
    Propagation
        Page 18
        Page 19
        Page 20
    Planting
        Page 21
        Page 22
    Fertilization
        Page 23
    Mulching and irrigating
        Page 24
    Thinning of fruit
        Page 24
    Picking, packing and shipping
        Page 24
        Page 25
    Yields and returns
        Page 26
    Developing new varieties and seed selection
        Page 26
        Page 27
        Page 28
        Page 29
    Diseases
        Page 30
    Insects
        Page 31
        Page 32
        Page 33
    Literature cited
        Page 34
        Page 35
Full Text
bulletin 350


October, 1940

PAPAYA CULTURE


IN FLORIDA


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EXECUTIVE STAFF
John J. Tigert, M. A., LL.D., President
of the University'
Wilmon Newell, D.Sc., Directors
Harold Mowry, M. S. A., Asst. Dir.,
Research
J. Francis Cooper, M.S.A., Editors
Jefferson Thomas, Assistant Editors
Clyde Beale, A.B.J., Assistant Editor'
Iaa Keeling Cresap, Librarian
Ruby Newhall, Administrative Managera
K. H. Graham, Business Managers
Rachel McQuarrie, Accountant"
MAIN STATION, GAINESVILLE
AGRONOMY
W. E. Stokes, M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomist8
Fred. H Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Associate2
W. A. Carver, PH.D., Associate
John P. Camp, M.S., Assistant
Roy E. Blaser, M.S., Assistant
ANIMAL INDUSTRY
A. L. Shealy, D.V.M., Animai Indus-
trialist3
R. B. Becker, Ph.D., Dairy Husbandman-
E. L. Fouts, Ph.D.. Dairy Technologist"
W. M. Neal, Ph.D. Asso. in An. Nutrition
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, D.V.M., Veterinarians
N. R. Mehrhof, M.Agr., Poultry Hus-
bandman'
W. G. Kirk, Ph.D., Asso. An. Husband-
man3
R. M. Crown, M.S.A., Asst. An. Husb'
P. T. Dix Arnold, M.S.A., Asst. Dairy
Husbandmans
L. L. Rusoff, Ph. D., Asst. in An.
Nutrition'
O. W. Anderson, M.S., Asst. Poultry
Husbandmans
SOILS
R. V. Allison, Ph.D., Chemist1 a
Gaylord M. Volk, M.S., Chemist
F. B. Smith, Ph.D., Microbiologists
C. E. Bell, Ph.D., Associate Chemist
H. W. Winsor, B.S.A., Assistant Chemist
J. Russell Henderson, M.S.A., Associate'
L. H. Rogers, M.S., Asso. Biochemist
Richard A. Carrigan, B.S., Asst. Chemist
ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agricultural
Economist '3
Bruce McKinley, A.B., B.S.A.. Associate
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant
ECONOMICS, HOME
Ouida D. Abbott, Ph.D., Home Econ-
omist1
Ruth Overstreet, R.N., Assistant
R. B. French, Ph.D., Asso. Chemist
ENTOMOLOGY
J. R. Watson, A.M., Entomologist3
A. N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturistx
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph. D,, Truck Hort.3
R. J. Wilmot, M.S.A., Fumigation
Specialist
R. D. Dickey, M.S.A., Asst. Horticulturist
J. Carlton Cain, B.S.A., Assistant
Horticulturist
Victor F. Nettles, M.S.A., Assistant
Horticulturist
F. S. Lagasse, Ph.D., Horticulturist2
H. M. Sell, Ph.D., Asso. Horticulturist2
PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist31
George F. Weber, Ph.D., Plant Path.8
L. O. Gratz, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist


BOARD OF CONTROL
H. P. Adair, Chairman, Jacksonville
W. M. Palmer, Ocala
Chas. P. Helfenstein, Live Oak
R. H. Gore, Fort Lauderdale
N. B. Jordan, Quincy
J. T. Diamond, Secretary, Tallahassee
BRANCH STATIONS
NORTH FLORIDA STATION, QUINCY
J. D. Warner, M.S., Agron. Acting in
Charge
R. R. Kinkaid, Ph.D., Asso. Plant Path.
Elliott Whitehurst, B.S.A., Assistant An.
Husbandman
Jesse Reeves, Asst. Agron., Tobacco
CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Horticulturist in
Charge.
John H. Jefferies, Asst. in Cit. Breeding
Michael Peech, Ph.D., Soils Chemist
L. H. Greathouse, Ph.D., Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Associate
Entomologist
F. F. Cowart, Ph.D., Asso. Horticulturist
W. W. Lawless, B. S., Asst. Horticulturist
R. K. Voorhees, M.S., Asst. Plant Path.
EVERGLADES STA., BELLE GLAF.E
J. R. Neller, Ph.D., Biochemist in
Charge
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
Physiologist
Frederick Boyd, Ph.D., Asst. Agronomist
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, B.S., Asst. An. Husbandman
W. T. Forsee, Ph.D., Asso. Chemist
B S. Clayton, B.S.C.E., Drainage En-
gineers
F. S. Andrews, Ph.D., Asso. Truck Hort.
SUB-TROPICAL STA., HOMESTEAD
W. M. Fifield, M.S., Horticulturist Act-
ing in Charge
S. J. Lynch, B.S.A., Asst. Horticulturist
Geo. D. Ruehle, Ph.D., Associate Plant
Pathologist
W. CENTRAL FLA. STA.,
BROOKSVILLE
W F. Ward, M.S., Asst. An. Husband-
man in Charges
FIELD STATIONS
Leesburg
M. N. Walker, Ph.D., Plant Pathologist
in Charge
K. W. Loucks, M.S., Assistant Plant
Pathologist
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
Hastings
A. H. Eddins, Ph.D., Plant Pathologist.
E. N. McCubbin, Ph.D., Asso. Truck
Horticulturist
Monticello
Samuel O. Hill, B.S., Asst. Entomologist2
Bradenton
Jos. R. Beckenbach, Ph.D., Truck Horti-
culturist in Charge
David G. Kelbert, Asst. Plant Pathologist
Sanford
R. W. Ruprecht, Ph.D., Chemist in
Charge, Celery Investigations
W. B. Shippy, Ph.D., Asso. Plant Path.
Lakeland
E. S. Ellison, Meteorologist2
B. H. Moore, A.B., Asst. Meteorologist2

'Head of Department
I2n cooperation with U.S.D.A.
sCooperative, other divisions, U. of F.










PAPAYA CULTURE IN FLORIDA
By H. S. WOLFE1 AND S. J. LYNCH


CONTENTS
PAGE PAGE
History ... ....... ...- ... 3 Thinning of Fruit. .... ........... 24
Botanical Relationships ..... .... 5 Picking, Packing and Shipping ... 24
Uses .. ... ...... .... ... 6 Yields and Returns ... .... .. 26
Flower Structure and Sex Variations 7 Developing New Varieties and
Climate and Soil.. ... 17 Seed Selection ......- 26
Propagation ..... 18 Diseases .. .... .... 3C
Planting ... ... 21 Insects .-- ----- -- -31
Fertilization .... .. .. ... ... ... 23 Literature Cited .. ...- 34
Mulching and Irrigation ....... 24

INTRODUCTION

One of Florida's minor fruit industries of interest to the
southern half of the state is the growing of papayas. Because
of the short life cycle of the plant, and the rapidity with which
large acreages can be put in and removed from production again,
the total area of plantings has fluctuated greatly from year to
year. In some years there have been several hundred acres
planted, while in other years plantings have totalled much less
than 100 acres. There was even a cooperative association of
papaya growers for a year or two during one of the periodic
booms of this industry, which has endured a succession of
overplantings and then underplantings. Now conditions seem
more stable in the papaya industry than at any period of its
history in Florida.

HISTORY

The papaya is a tropical fruit of such wide distribution that
it is often hard to believe that it is not indigenous to parts of
Asia or Africa where it has long been a staple food. It was,
however, unknown to the Old World until seeds were brought
there by early Spanish and Portuguese sailors from the Ameri-
can tropics. The exact extent of its early distribution is not
known, but there is good reason to believe that southern Mex-
ico may have been the original home of the papaya (16).2 It

iFormerly Horticulturist in Charge, Sub-Tropical Experiment Station.
Now Head, Department of Horticulture, College of Agriculture.
2Italic figures in parentheses refer to literature cited in the back
of this bulletin.










PAPAYA CULTURE IN FLORIDA
By H. S. WOLFE1 AND S. J. LYNCH


CONTENTS
PAGE PAGE
History ... ....... ...- ... 3 Thinning of Fruit. .... ........... 24
Botanical Relationships ..... .... 5 Picking, Packing and Shipping ... 24
Uses .. ... ...... .... ... 6 Yields and Returns ... .... .. 26
Flower Structure and Sex Variations 7 Developing New Varieties and
Climate and Soil.. ... 17 Seed Selection ......- 26
Propagation ..... 18 Diseases .. .... .... 3C
Planting ... ... 21 Insects .-- ----- -- -31
Fertilization .... .. .. ... ... ... 23 Literature Cited .. ...- 34
Mulching and Irrigation ....... 24

INTRODUCTION

One of Florida's minor fruit industries of interest to the
southern half of the state is the growing of papayas. Because
of the short life cycle of the plant, and the rapidity with which
large acreages can be put in and removed from production again,
the total area of plantings has fluctuated greatly from year to
year. In some years there have been several hundred acres
planted, while in other years plantings have totalled much less
than 100 acres. There was even a cooperative association of
papaya growers for a year or two during one of the periodic
booms of this industry, which has endured a succession of
overplantings and then underplantings. Now conditions seem
more stable in the papaya industry than at any period of its
history in Florida.

HISTORY

The papaya is a tropical fruit of such wide distribution that
it is often hard to believe that it is not indigenous to parts of
Asia or Africa where it has long been a staple food. It was,
however, unknown to the Old World until seeds were brought
there by early Spanish and Portuguese sailors from the Ameri-
can tropics. The exact extent of its early distribution is not
known, but there is good reason to believe that southern Mex-
ico may have been the original home of the papaya (16).2 It

iFormerly Horticulturist in Charge, Sub-Tropical Experiment Station.
Now Head, Department of Horticulture, College of Agriculture.
2Italic figures in parentheses refer to literature cited in the back
of this bulletin.










PAPAYA CULTURE IN FLORIDA
By H. S. WOLFE1 AND S. J. LYNCH


CONTENTS
PAGE PAGE
History ... ....... ...- ... 3 Thinning of Fruit. .... ........... 24
Botanical Relationships ..... .... 5 Picking, Packing and Shipping ... 24
Uses .. ... ...... .... ... 6 Yields and Returns ... .... .. 26
Flower Structure and Sex Variations 7 Developing New Varieties and
Climate and Soil.. ... 17 Seed Selection ......- 26
Propagation ..... 18 Diseases .. .... .... 3C
Planting ... ... 21 Insects .-- ----- -- -31
Fertilization .... .. .. ... ... ... 23 Literature Cited .. ...- 34
Mulching and Irrigation ....... 24

INTRODUCTION

One of Florida's minor fruit industries of interest to the
southern half of the state is the growing of papayas. Because
of the short life cycle of the plant, and the rapidity with which
large acreages can be put in and removed from production again,
the total area of plantings has fluctuated greatly from year to
year. In some years there have been several hundred acres
planted, while in other years plantings have totalled much less
than 100 acres. There was even a cooperative association of
papaya growers for a year or two during one of the periodic
booms of this industry, which has endured a succession of
overplantings and then underplantings. Now conditions seem
more stable in the papaya industry than at any period of its
history in Florida.

HISTORY

The papaya is a tropical fruit of such wide distribution that
it is often hard to believe that it is not indigenous to parts of
Asia or Africa where it has long been a staple food. It was,
however, unknown to the Old World until seeds were brought
there by early Spanish and Portuguese sailors from the Ameri-
can tropics. The exact extent of its early distribution is not
known, but there is good reason to believe that southern Mex-
ico may have been the original home of the papaya (16).2 It

iFormerly Horticulturist in Charge, Sub-Tropical Experiment Station.
Now Head, Department of Horticulture, College of Agriculture.
2Italic figures in parentheses refer to literature cited in the back
of this bulletin.






4 Florida Agricultural Experiment Station

is mentioned by Oviedo (12) in 1526 as a common fruit in
Central America, but it is conspicuously absent from the list of
Cuban fruits given by Alvas (15) in his account of DeSoto's
expedition in 1540.
Following its discovery in the New World the papaya was
soon carried to the tropics of the Old World, where it flourished.
The Dutch traveler Linschoten (8), in 1596, wrote of seeing it
cultivated in India, whither it had been introduced from the
West Indies by way of Molukka. Forster (5) failed to find it
growing in the islands of the Pacific in the middle of the
18th century, when Captain Cook explored that region, but by
1823 the papaya had reached Hawaii (6), where it has long been
one of the most valuable fruits for home consumption.
The papaya is now cultivated extensively in India, Ceylon,
Malaya, the East Indies, Australia, South Africa, Central Amer-
ica, Mexico and the warmer parts of South America. In the
United States it is principally grown in Florida, but there is
a limited culture of it in Texas and California, in the relatively
frost-free areas of these states. The date of its introduction into
Florida is unknown, as it was not considered important enough
to mention among the fruits being planted by the Spanish
settlers. The introduction must have been fairly early after the
establishment of Spanish settlements on the East Coast, however,
for in 1773 Bartram (2) reported finding it apparently wild
on the low bluffs along the St. John's River near Palatka and
even more abundantly near where Sanford now is located. He
described the fruits as being only the size of a pear. A little
less than a century later, Atwood (1) mentioned papayas as
among the fruits in the gardens of St. Augustine, and only
the same inferior, small, wild type was known to him also.
In an account of the tropical fruits being grown near Fort
Myers in 1851, it is surprising to find no mention of the
papaya (18), and the same is true of an account in 1871 of fruits
grown on the Florida Keys (10). When Pliny Reasoner (14)
reported in 1887 on tropical horticulture in the state of Florida,
the papaya was decidedly one of the minor fruits, although large
fruited types were well known by then. Indeed, the papaya
has the distinction of Being the basis of the only fruit industry
of even semi-commercial importance in Florida today which
was not already well started 50 years ago.






Papaya Culture in Florida


BOTANICAL RELATIONSHIPS
The papaya is known to botanists as Carica papaya L., a name
regarding which there has been no dispute. Originally as-
signed to the Passion-flower family, it has long since been made
the type of the family Caricaceae. There is much disagree-
ment among taxonomists, however, as to the number of genera
among which the species in this family should be distributed,
some dividing the genus Carica into two genera, Carica and Jacaratia,
and others retaining all the species within this genus. Except
for the African genus Cylicocarpa, with two species, the species
of the Caricaceae are all American, and are tropical or sub-
tropical. Only C. candamarcencis is of economic interest among
the relatives of the papaya. This is the so-called mountain papaya
of the Andean highlands, whose small, rather acid fruits are used
for preserves. Repeated efforts to establish this species in Flor-
ida have failed.
One of the subtropical species, sometimes listed as Carica
dodecaphylla and sometimes as Jacaratia dodecaphylla, has attracted
attention in Orlando because of its comparative hardiness and
large size. As the specimen is a male tree and has never de-
veloped any fruits, it is not possible to judge of its possible
usefulness for fruit, and attempts to use its pollen in breeding
papayas are reported as failures. Many seeds were distributed,
but apparently only this one specimen has grown to maturity
and still lives.
The family Caricaceae is also the subject of dispute among
taxonomic authorities as to its relationships. Probably the
majority of the experts on classification consider the Caricaceae
to be closely related to the Passifloraceae, with which Bentham
and Hooker included it originally. Some authorities, however,
stress the resemblances of the papaya to the true melons, and
believe the Caricaceae derived from the same lines as the
Cucurbitaceae. -
The papaya plant is really a gigantic herb, rather than a tree,
/since it never develops a typical woody stem. Usually the trunk
lis unbranched in C. papaya, although when the top of the plant
is killed or cut off, branches develop readily from lateral buds,
and branching is common in plants over five or six years old.
Because of the tall, unbranched stems, and the large, spread-
ing leaves, the papaya is often likened to a palm. It is much
more aptly compared to a castor bean plant. Papayas may live to
be 15 or 20 years old and such plants are 25 or 30 feet high,






Florida Agricultural Experiment Station


with trunks up to a foot in diameter. Ordinarily it is not
profitable to allow plants to live for more than three years, as
with increasing size and age of the tree its fruits are smaller
and borne farther from the ground, and the leaves also are
smaller. It is more profitable in commercial plantings, and
more satisfactory in home plantings, to make a new planting
each year, replacing that of two years previous, so that one has
always a new planting coming on and a mature planting in
bearing.
One of the important characteristics of the papaya is the pres-
ence in all the superficial portions of the plant of latex tubes
containing milky juice. While the leaf and the outermost part
of the stem contain this latex, it is most easily obtained by
scoring the very thin skin of the green fruit. This latex contains
the enzyme papain, which digests protein. As the fruit ripens
the flow of latex diminishes, and fully ripe fruit neither yields
any latex when the skin is cut nor does it contain any appre-
i ciable quantity of the digestive enzyme.

USES
The papaya is essentially a flavor fruit, esteemed for its re-
freshing qualities, since it has a high water content (nearly
90%) and contains very little actual nourishment. Sugar content
of Florida papayas has been found to vary from about 4 to 10
percent of the fresh weight of the pulp (9). Vitamins A, B
and C are supplied in fair quantity by the papaya.
Until quite recent years the papaya was valuable in Florida
only as a fresh fruit. A good variety provides an excellent
dish when served "on the half shell" as cantaloups are, and in
tropical countries the papaya has long been very popular for
this usage. It is also excellent as an ingredient of fruit salads.
Other home uses of papayas have included the preparation of
sweet pickle and crystallized fruit from the mature but still
firm fruit. The green fruits, when almost mature, are cooked
and eaten as summer squash, making a pleasant addition to the
diet. Pies, jams and preserves are made from the firm mature
pulp. The milky juice from green fruit has yielded a digestive
enzyme, papain, which is a commercial product in Ceylon and
Montserrat, but costs of production are too great under Florida
conditions to make this industry attractive.
In the last decade there has been developed in Florida a
considerable industry devoted to processing ripe papayas for







Papaya Culture in Florida


various canned products. Chief among these are soft drinks,
either carbonated or not, which have a base of ripe papaya pulp
usually fortified by citric acid and sugar. Several trade-marked
papaya drinks are now on the market. Experimental work is
still being done on the use of ripe papaya as a base for ice
cream, sherbets and ices. A papaya paste similar to the guava
paste so popular in the West Indies is made from the flesh of
the ripe fruit. The "green mature" fruit is processed com-
mercially for crystallized fruit, salad balls in colors, and sweet
pickle preserves. The latex has been put on the market in water
solution for use as a meat tenderizer. A number of cosmetic
products are manufactured with the papaya pulp as an ingredi-
ent, such as face creams and hair shampoos.
The fruit production in Florida has increased considerably and
except in a few instances has been sufficient to meet the de-
mands of the manufacturing plants, as well as the fresh fruit
markets. From time to time there have been some importations
of the ripe fruit from Cuba by the manufacturers, particularly
following a freeze or a hurricane when the local supply is tem-
porarily curtailed. However, the fresh fruit markets are sup-
plied almost entirely by Florida-grown fruit.

FLOWER STRUCTURE AND SEX VARIATIONS
Flower Types.-The papaya plant may be said to be normally
dioecious or unisexual, i. e., to have "male" and "female" flowers
on separate plants, and all the earlier botanical descriptions so
indicated them. The Carica hermaphrodita described by Blanco
(3) in the Philippines in 1837 was only a fruiting male tree, and
not a true bisexual type as the name suggests. Seed of the bi-
sexual type of papaya was first sent to Hawaii from Ceylon in
1896 (6), and reached the United States much more recently.
We know nothing of its origin. The papaya is notable, however,
for the number and degree of the variations of its flowers from
these three types, and especially for the numerous intergrading
forms. These have been more carefully studied in Hawaii
than anywhere else, and the recent summary of the views of
the workers at the Hawaii Experiment Station (19) will be
followed as a basis for discussion. Five basic flower types are
recognized, as follows:
Type I.-"Female" or pistillate flower (Fig. 1, left). This
is characterized by having neither stamens nor rudiments of
stamens, and by having the petals free to the base, so that the







Florida Agricultural Experiment Station


Fig. 1.-Pistillate (left) and hermaphrodite (right) flowers of papaya.


Fig. 2.-The same flowers as in Fig. 1, with near petals removed to
show interior of flowers.






Papaya Culture in Florida


fruit shows five separate scars where the petals fell off. The
flowers are large, from 2 to 21/ in. long, and are either borne
singly in the leaf axils or in small cymose clusters. Within
the petals is easily seen the large ovary (Fig. 2, left), either
smoothly circular in outline or having five shallow lobes, and
surmounting it are the five sessile stigmas, fan-shaped and
much lobed. The ovary is often spoken of as the young fruit, but
this designation is incorrect until after pollination has occurred
and growth begun. The matured fruit may weigh anywhere
from 12 oz. to 12 lbs., but is usually from 2 to 5 lbs. in weight.
It varies in shape from somewhat spherical to oblong or pyri-
form, but usually has a body cavity which is large in comparison
with the thickness of the walls and is more than half the diam-
eter of the whole fruit (Figs. 3, 4, 14).
Type II.-Pentandria flower (Fig. 5). This resembles the
pistillate flower very closely in size and outward appearance, but
differs strikingly from it in the possession of five stamens-
whence the name-which alternate with the petals. These petals
are free nearly to the base, but form a narrow ring there, so
that a circular scar is left on the fruit when they fall. From
this narrow corolla tube the stamens arise on long filaments
which lie in deep grooves in the ovary wall. These grooves


Fig. 3.-Typical fruit of unisexual (female) type of plant, 8 inches
long. Betty variety.






10 Florida Agricultural Experiment Station

persist in the mature fruit, which is rounded but deeply 5-lobed.
The fruit of the pentandria flowers is very characteristic and
unmistakable.
Type III.-Intermediate type. This is not a single and definite
type, but is rather a group in which are included many ab-
normalities of form. The only common characteristic is that the
flowers do not fit into any of the other types, and either flowers
or fruit or both are variously misshapen or distorted. Petals
may be nearly free or connate in varying degree, not necessarily

Fig. 4.-Female papaya tree with first mature fruit, eight months
from setting in the field. Betty variety.







Papaya Culture in Florida


symmetrically so. Stamens may be any number from 2 to 10,
but may be partially adnate to the ovary wall and even variously
pistilloid, i. e., transformed into defective pistils. The pistil
itself is frequently distorted, and may have from 5 to 10 carpels.
Often these carpels fail to make a complete union, leaving one


Fig. 5.-Pentandria Flower (center) with near petals removed. Small
side blossoms are from same pedufcle.






12 Florida Agricultural Experiment Station

side of the pistil open. Fruit from such defective pistils, or from
those where one or more stamens have adhered, is more or
less misshapen.
' Type IV.-Bisexual or hermaphrodite type (Fig. 1, right).
This is the normal perfect flower, to which the name Elongata
type was given in Hawaii because the fruit is characteristically
elongated and subcylindrical, in contrast with the more rounded
form of the female type. In the usual bisexual form the flowers
are borne in short cymose clusters, from 3 to 5 in. long on
stout peduncles, the individual flowers being from 11/2 to 2 in. in
length. The corolla is gamopetalous, with the tube nearly as long
as the free lobes or petals, and is free from the pistil. There
are 10 stamens, arranged in two series on top of the corolla tube.


















Fig. 6.-Typical fruit of bisexual type of plant, 12 inches long.
Standard Blue-stem variety.

Five stamens are alternate with the petals and have filaments
about twice as long as the anther sacs, while the other five
are opposite the petals on short filaments, hardly as long as the
anthers. All of the stamens are functional. The filaments are
united into a ring adnate to the corolla tube, making a thick
collar around the pistil. The pistil is composed of 5 carpels
usually, and has sessile upon it the 5 stigmas as in Type 1.
Both pistil and stigmas are smaller than in the female flower,
however (Fig. 2, right). The fruit is always elongated in form,
often with a smoothly cylindrical basal half where the corolla







Papaya Culture in Florida


tube compressed it, and expanding somewhat at the upper end,
but variations in form from pyriform to cylindrical are found.
The typical bisexual fruit is 10 to 12 in. long, nearly half that
thick, and weighs from 6 to 8 Ibs. (Figs. 6 and 7), but much
smaller fruited types have been selected (Fig. 13). Usually the
cavity is less than half the fruit diameter.


Fig. 7.-Bisexual papaya tree with first fruit maturing 11 months from
seed.


The clusters of hermaphrodite flowers are rarely all alike.
Always the terminal flower of the cyme is perfect, but the lateral
flowers may be staminate, or perfect flowers with poorly de-
veloped stigmas, or pentandria type.






14 Florida Agricultural Experiment Station
What is essentially a small model of this bisexual type flower
is found frequently in the staminate flower clusters on the long
peduncles of the male trees (Fig. 8). The flowers are much
smaller, being only about half the size of the perfect flowers
on t he bisexual
type plants, but
they are other-
wise similar in
structure and
function.
T3 Type V.-
"Male" or stam-
inate flowers
(Fig. 9). These
flowers are char-
acterized at once
by their lack of
any stigmas and
by the great
length and slend-
erness of the co-
rolla tube, which Fig. 8.-Perfect flower on a staminate cluster.
is twice as long A fruit may set from such a flower on a male tree.
as the free corolla lobes or petals. There are 10 stamens,
arranged as in the Type IV flower, but the pistil is reduced
to a mere rudiment, with no stigma and incapable of function-
ing. Consequently the staminate flowers cannot produce fruit.






V %--,,A


Fig. 9.-Staminate flower cluster and individual flowers. Note rudi-
mentary pistil in middle flower, cut open.







Papaya Culture in Florida


1617 1


Fig. 10.-Male papaya tree with several fruits developed from perfect
flowers on tips of the old inflorescences 10 months from seed.

On male trees the flowers are produced in small clusters
which are in turn borne on long pendant peduncles in racemose
form (Fig. 10). Staminate flowers appear also in the short
cymose clusters on bisexual trees. The staminate flowers of
male trees produce potent pollen, but Higgins and Holt (6)
reported the pollen from staminate flowers on bisexual plants
as unable to cause fruit to set with any type of flower tried.






16 Florida Agricultural Experiment Station

Sex Variations.-While these five classes of flower types can
be considered as fairly basic, it must be remembered that numer-
ous intergrade forms are found in addition. Furthermore, with
the exception of Type I, all of the forms may be replaced by
some other one as the plant grows older. No case has yet been
reported of production of any other flower type on dioecious
female trees than Type I. The pentandria type resembles the
pistillate flower very closely, but never seems to arise as a
modification of it. Rather, it is commonly found on bisexual
type trees. The bisexual plant which produces Type IV perfect
flowers early in life may produce either staminate or pentandria
flowers at any time, along with the bisexual type, and also the
intermediate type may appear without much apparent reason.
There is some evidence that variations are more common in a
given strain when it is grown in a cooler climate.
The bearing of fruit by the male trees has given rise to many
misinterpretations. The staminate flowers are unable to pro-
duce fruit, as explained above, because of imperfect pistils. As
the trees get older, some of the flowers which are produced
have a perfect pistil (Fig. 8), so that they are really of Type IV,
although they are borne on the same long peduncles as the
staminate flowers and are much smaller than the usual her-
maphrodite flowers. Such trees may bear a considerable quan-
tity of fruit (Fig. 10), although it is always of small size, and
in both Florida and Hawaii they seem to bear earlier when
grown in a cooler climate, such as at higher altitudes or further
north, than in a more nearly tropical location.
In particular there have been misconceptions regarding the re-
lation of the fruiting of male trees to previous severe pruning.
Experiments at the Florida station have confirmed those re-
ported from Hawaii (13) as to the lack of any predictable effect
on the flower type from cutting male trees back. Rare in-
stances have been reported of male trees which produced only
pistillate flowers after severe pruning of the top, but in many
other instances male trees have been cut nearly to the ground
and have continued to produce staminate flowers as before. The
majority of fruiting male trees have never been pruned at all.
Change of sex completely from male to female, in the very rare
cases of its occurrence, is probably the result of bud mutation
and is quite independent of the cutting itself.
In both Hawaii (20) and South Africa (7), research workers
have developed fairly pure lines of papaya for study of genetic






Papaya Culture in Florida


behavior. Using female, male and bisexual plants of such lines,
hand pollinations have given the following results:
1. Female pollinated by male gives equal numbers of male
and female progeny.
2. Female pollinated by bisexual gives equal numbers of
female and bisexual progeny.
3. Bisexual pollinated by male gives equal numbers of female,
bisexual and male progeny.
4. Bisexual self-pollinated gives largely bisexual, with the
balance mostly female and sometimes a trace of males.
It is hardly necessary to point out that the fruits from flowers
of the intermediate group are undesirable in appearance, and
that every effort should be made to breed out such production
in the selection of breeding strains.

CLIMATE AND SOIL
The papaya is decidedly tropical in its requirements of tem-
perature, although not so closely limited in its range as many
other tropical plants. It has a temperature requirement very
much like the West Indian race of avocado, i. e., can endure
light frosts if the plants are not too tender, but it prefers and
thrives best under frostless conditions. t Successful cultivation
of the papaya can be expected only along the lower East and
West Coasts of Florida, and perhaps in a few localities in the
lower Ridge section where air drainage is unusually good.
However, there is a much more extensive area of the state in
which papaya culture is possible whenever mild winters permit
the mature plants to live through until the next year. As far
north as Daytona Beach on the East Coast and Tampa on the
West Coast, papaya culture may be carried on in the coastal
areas during such years. ( Plantings north of Palm Beach or
Bradenton are much less safe than those south of these points,
although even at Miami there have been years when papayas
were badly injured by frost. I
Apart from considerations of cold resistance and frost injury,
the papaya is also limited by temperature for another reason.
The flavor of the fruit seems to be definitely correlated with
the temperature at which the fruit matures. Temperatures
not low enough to injure the plant may yet mar the flavor
of the fruit and make it insipid.






Florida Agricultural Experiment Station


The soil requirements of the papaya are very elastic. Like
the avocado again, it can thrive on almost any type of soil pro-
viding there is adequate drainage. Naturally it grows more
luxuriantly on rich soils than on poor ones, but it can be grown
successfully on high sandy soils, hammock soils, limerock soils
and others.' On the marl glades of southern Dade County the
plant grows vigorously but the fruit is often of poor flavor.
The same is true of the muck soil of the Everglades. Growth
is phenomenal and tremendous crops are produced, but quality
iis inferior.
Low, marshy ground, or that subject to periodic overflow,
should be avoided for growing papayas. If it must be used, it
should have beds thrown up two or three feet above the water
table. A period of 48 hours with the water standing up around
the crown roots is likely to prove fatal to the plant.

PROPAGATION
The only practicable method of propagating papayas is by
seed. Cuttings root fairly readily under good conditions but do
not make as vigorous plants as seedlings and the number o
cuttings available is always very small, owing to the non-
branchig habit of the papaya. It is possible, also, to graft from
particularly fine plants on seedling stocks, but the type runs
out soon and propagating material io vcry limited.
The usual practice has been to sow the seeds in flats or in
seedbeds in the open ground. This practice, however, necessi-
tates transplanting the seedlings once or twice before setting
them in the open field, and such transplanting is made almost
bare-root, with resulting retardation of growth following each
transfer. It is important that plants should be brought into bear-
ing before they grow very tall, and there is reason to believe
that bearing is retarded when the taproot is injured. By growing
the seedlings for each hill in a community pot, so that they can
be set out in the field without any disturbance of the roots
from the very start and with plenty of pot depth for good
root development, the grower can bring plants into bearing
in from one to three weeks sooner than by the usual trans-
planting.
Bottomless cups made of 15-lb. asphalt felt paper, as shown
in Fig. 11, have proven quite successful for use as community
pots. The cost of the materials is less than 1/ cent per cup, and






Papaya Culture in Florida 19















Fig. 11.-Construction of asphalt-felt paper cylinders for use as
community pots.

the labor required is very little. A roll of paper is sawed
into 5 sections, each about 7 inches wide. Each section is unrolled
and cut into pieces 14 inches long. The resulting pieces are
curled into cylinders with an inch overlap, and are held in shape
by two corrugated roofing nails pressed through the overlapping
portion as shown in the figure, giving cylinders 7 inches high
and 4 inches in diameter. These cylinders can be set on boards
or on strips of the felt paper, leaving a passageway between
each four rows. A handful of peat moss in the bottom of each
cylinder facilitates drainage.
Standard 6-inch clay pots or 1-quart oil cans may be used
as community pots quite satisfactorily, but the clay pots are
expensive and the cans are difficult to handle when setting out.
Cans to be used should be cut down one side and across the
bottom before being filled with soil. A single wire band will
hold the can together, and on its removal at setting out time
the can is easily pulled away from the soil cylinder.
A rich loamy soil, or a mixture of two parts of light sandy
loam with one part well rotted manure or peat moss, should
be used as a medium of germination. Pots should be filled to
within about an inch from the top, after the soil is firmed. In
each community pot should be planted 5 or 6 seeds of a bisexual
type of papaya or 7 or 8 seeds of a unisexual type, spacing the
seeds well apart on the firmed soil and then covering them with
1/4 to 1/2 inch of soil. Watering should be done frequently
enough to prevent the top inch of soil from becoming dry, but
not so often or so copiously that the soil becomes saturated.






Florida Agricultural Experiment Station


Small papaya seedlings are subject to damping-off, and the
soil for the pots or flats should be sterilized if possible. Ster-
ilization may be accomplished by live steam or by a solution
of formalin. Somewhat less satisfactory are certain proprietary
organic mercury compounds and formaldehyde dust. The
simplest satisfactory procedure is to pour 1 pint of commercial
formalin into 6 gallons of water, and with this saturate the soil
in the cylinder pots or flats. The soil surface should be covered
for 24 hours with several thicknesses of newspaper, to avoid
loss of the formaldehyde fumes, and the soil should be allowed
to stand for 10 days before seeds are planted in it.
From two to three weeks usually is required for appearance of
seedlings after planting, the time of germination varying with
the temperature. Under very favorable conditions seedlings may
appear in 10 days, while in cool weather they may not appear
for a month. Seed taken directly from a fruit germinate at the
same rate as seed which have been dried.
Seedlings are ready to set in the field when they have reached
a height of about 4 inches, usually attained in from two to three
months from planting (Fig. 12). At this time the plants in each
community pot should be thinned by removal of the weaker
seedlings, leaving three in each pot of the bisexual type and four
of the unisexual type. Shade grown plants should be hardened
for field conditions by being transferred to a sunny location for
a week before setting.





*S '









Fig. 12.-Papaya plants in community pots of felt paper. Left, plants
60 days old ready to set in field; center, plants 45 days old; right, pots
just planted.






Papaya Culture in Florida


If flats or seedbeds are used seeds should be planted 1 inch
apart in rows 3 inches apart. The seedlings should be trans-
planted as soon as they have developed the third leaf, usually
m about three weeks from germination. Transplanting may be
to pots or cans, or to a nursery row. In the latter case the
seedlings should be spaced at least 3 inches apart in rows 6 inches
apart, to permit final setting out with as much root system
as possible. Pots should be at least the 3-inch size, and cans
of similar diameter, with holes in the bottom for drainage. In
any case, the seedlings should be set in the field when about
4 inches high, as later planting means greater proportional loss
of root system. Plants can be set in the field when more than
two feet high, if grown in large enough containers or in deep
seedbeds, but it is not a desirable practice to allow them to
become more than 6 inches high before setting.
Since plants cannot safely be set in the field until late March
or April in many sections of Florida, seed should not be planted
in such areas until January. In the warmer parts of the state,
where most papayas are grown, they can be set in the field at
any time of year. However, best results are obtained even here
by planning to set out plants in March or April, so that they
have all spring and summer-the period of most favorable
growing conditions-for developing to the fruiting stage. The
first fruit will probably mature in November, or perhaps in Oc-
tober, from January seeding, and the mature plants will bear all
winter and all the succeeding year. In the colder sections of the
state the plants can hardly do more than reach maturity by
the end of the first year, but if the winter is exceptionally mild
the plants should fruit well the second year.

PLANTING
Holes for papayas should be 8 to 10 feet apart, both in the
row and between the rows. ( Since thepapaya-is very particular
about good drainage, it is important to make careful arrange-
ments for this in low ground. The rows should be on beds with
a good water furrow between every pair of rows. Holes should
be excavated to a depth of a foot and a width of two feet in
sandy soil. On the rocky soil of southern Dade County it will
be advantageous to blast shallow holes or to scarify very deeply
down the rows. Half a bushel of well rotted stable manure,
or better still, of chicken manure, should be put in each hole
and mixed with the top soil returned to the hole. If no manure






Florida Agricultural Experiment Station


is available 5 pounds of high grade fish tankage or guano
is recommended for mixing with the soil in the hole.
Plants grown in community pots should have the container
removed from about the soil cylinder before they are set. With
the felt paper pots the whole pot can be set at the proper soil
depth and the paper removed without disturbing the soil cylinder
at all. Then the top soil is filled in around the soil cylinder.
With tin cans which have been cut before filling with soil, more
care is needed in handling if the soil and plants are to be set
without disturbance. Where individual plants have been grown
in small tin cans they should be removed from the cans before
being set, lest the can rust too slowly and roots be hindered in
development.
If plants have been transplanted to nursery rows instead of
being potted, it is well to cut through the soil between the plants
both ways before lifting. Then each section of soil with a plant
in the center can be lifted out nearly entire, with little disturb-
ance of the root system. If plants have been allowed to re-
main in the nursery row so long that considerable injury to the
roots must occur on setting, the older leaves should be cut off
just at the juncture of the blade with the leaf-stalk, leaving only
the partly developed terminal leaves.
Plants should not be set any lower in the ground than they
were in the pot or nursery row. Rather they should be set a little
higher to allow for later settling of the soil. The papaya plant
will quickly decay around the base at ground level if water
can collect there permanently. Having set the plants and firmed
the soil around them, a shallow basin should be made around
the hill, with a diameter of a foot or so. fA thick mulch of grass,
peat moss or any other material which will hold water and
shade the ground should be placed around the plants in this basin.
Water should be applied liberally every few days until the
plants are well established./
With plants of the unisexual type it is best to set four in a
hill, spaced 2 inches apart. When these reach blooming age,
so that their sex can be distinguished, the males or weak females
can be removed, leaving the bearing plants in place. Usually
this practice will assure the presence of at least one female in
each hill. In rare instances where no vigorous female is present
in a hill, one can be transplanted from a hill with excess strong
females.f In such case it is important to observe the precautions






Papaya Culture in Florida


indicated above for plants left too long in the nursery row.
Similarly, in case of bisexual types it is well to set three plants
in each hill, to allow for removal of off-type or weak plants at
blooming. It will be observed that plants grown in community
pots will already have the proper number for a hill in each pot.
In order to assure pollination in plantings of the unisexual type,
at least one male plant should be left in the field for each 24
female plants. Leaving a male in every fifth hill in every
fifth row will accomplish this. No hill should contain more
than one plant.
FERTILIZATION + ~7ad-
The papaya plant makes a very vigorous and rapid growth if
well fed, and as plants which are kept in healthy growing condi-
tion constantly are most likely to yield profitable crops of fruit,
it behooves the grower to see that his plants have plenty of nour-
ishment. The experience of successful growers indicates that
during the first six months after plants are set in the field a
fertilizer high in nitrogen and relatively low in phosphate and
potash may be used. Chicken manure is a favorite fertilizer for
young papayas, and both guano and fish tankage are highly
esteemed. Ten pounds of chicken manure should be applied
every 30 days, beginning about a month after setting, and con-
tinued until the first fruit is nearly full size. If guano, tankage,
cottonseed meal or castor pomace is used, the amounts may be
considerably reduced. One pound of 16% guano equals 2 pounds
of 8C, cottonseed meal, about 15 pounds of chicken manure or
about 25 pounds of stable manure. This gives a rough indication
of how to judge quantities.
Excellent results have been had by many growers by using
commercial mixed fertilizers from the start. Beginning about
three weeks after the plants are set in the field, a 4-8-5 mixture
with from 25 to 40% of the nitrogen from organic sources is
applied monthly until fruiting, the amount per hill being about
/2 lb. at first and increasing to 1 lb. per hill toward the end of
the period. When fruit begins to set, a change is made to a
mixture with a 4-8-10 ratio, since papaya fruit contains con-
siderable potash, and 1 lb. per hill is applied every month. This
rate of application is continued as long as yields warrant keeping
the plants. In case trees show by the yellowish green of the
foliage that they are not being given sufficient nourishment,
as is likely to occur with unusually large trees or on very thin
soils, the amount may be increased to 11/ lbs. per hill.






Florida Agricultural Experiment Station


Roots of the papaya will forage widely and fertilizer should
be spread out over the whole feeding area of the roots, not
simply dumped near the trunk of the plant.

MULCHING AND IRRIGATING
The papaya plant should be ke t in active and vigorous
growth at all times, if its culture is t be successful. For this
end, regular and frequent applications o fertilizer are not suf-
ficient. The plants need a heavy mulch f grass, peat moss,
sawdust or some other material which will conserve moisture
and protect the soil from overheating ,as well as from drying.
This will also help control root-knot.
In a small backyard plot of 100 /trees or less, watering can
be done with a garden hose. WWhn papayas are grown on a
larger commercial scale, careful consideration should be given
to irrigation facilities. Successful papaya culture requires abund-
ant supply of water for the plants. Once checked in their
growth, papaya trees never recover satisfactorily.

THIINNINGOF FRUIT
Sometimes several papaya fruit set in a cluster, instead of
only a single fruit at each node. Unless the fruit is of small
size there is likely to be some damage resulting from crowding
with some fruit broken off by its own weight when another
offers leverage. Control of insects is more difficult also when
fruit is crowded, and many fruit may be deformed by pressure.
Under such conditions it will probably pay to thin the clusters
of fruit, leaving not more than two at a node, or even a single
fruit only when they are above 4 or 5 pounds weight at ma-
turity. The sooner this is done after the fruit is set, the better.

PICKING, PACKING AND SHIPPING
The papaya fruit usually turns yellow at maturity, the imma-
ture fruits being a dark green color. Fruit for shipping should
be picked when distinct traces or streaks of yellow color are
visible. At this stage fruit will ripen with practically as good
flavor as will fruit allowed to mature fully on the plant, and
it will still carry for several days before becoming soft. Fruit
wanted for local consumption should be left for one or two
days longer than fruit for shipping, but should rarely be left
on the tree until full yellow color has developed. Such fully






Florida Agricultural Experiment Station


Roots of the papaya will forage widely and fertilizer should
be spread out over the whole feeding area of the roots, not
simply dumped near the trunk of the plant.

MULCHING AND IRRIGATING
The papaya plant should be ke t in active and vigorous
growth at all times, if its culture is t be successful. For this
end, regular and frequent applications o fertilizer are not suf-
ficient. The plants need a heavy mulch f grass, peat moss,
sawdust or some other material which will conserve moisture
and protect the soil from overheating ,as well as from drying.
This will also help control root-knot.
In a small backyard plot of 100 /trees or less, watering can
be done with a garden hose. WWhn papayas are grown on a
larger commercial scale, careful consideration should be given
to irrigation facilities. Successful papaya culture requires abund-
ant supply of water for the plants. Once checked in their
growth, papaya trees never recover satisfactorily.

THIINNINGOF FRUIT
Sometimes several papaya fruit set in a cluster, instead of
only a single fruit at each node. Unless the fruit is of small
size there is likely to be some damage resulting from crowding
with some fruit broken off by its own weight when another
offers leverage. Control of insects is more difficult also when
fruit is crowded, and many fruit may be deformed by pressure.
Under such conditions it will probably pay to thin the clusters
of fruit, leaving not more than two at a node, or even a single
fruit only when they are above 4 or 5 pounds weight at ma-
turity. The sooner this is done after the fruit is set, the better.

PICKING, PACKING AND SHIPPING
The papaya fruit usually turns yellow at maturity, the imma-
ture fruits being a dark green color. Fruit for shipping should
be picked when distinct traces or streaks of yellow color are
visible. At this stage fruit will ripen with practically as good
flavor as will fruit allowed to mature fully on the plant, and
it will still carry for several days before becoming soft. Fruit
wanted for local consumption should be left for one or two
days longer than fruit for shipping, but should rarely be left
on the tree until full yellow color has developed. Such fully






Florida Agricultural Experiment Station


Roots of the papaya will forage widely and fertilizer should
be spread out over the whole feeding area of the roots, not
simply dumped near the trunk of the plant.

MULCHING AND IRRIGATING
The papaya plant should be ke t in active and vigorous
growth at all times, if its culture is t be successful. For this
end, regular and frequent applications o fertilizer are not suf-
ficient. The plants need a heavy mulch f grass, peat moss,
sawdust or some other material which will conserve moisture
and protect the soil from overheating ,as well as from drying.
This will also help control root-knot.
In a small backyard plot of 100 /trees or less, watering can
be done with a garden hose. WWhn papayas are grown on a
larger commercial scale, careful consideration should be given
to irrigation facilities. Successful papaya culture requires abund-
ant supply of water for the plants. Once checked in their
growth, papaya trees never recover satisfactorily.

THIINNINGOF FRUIT
Sometimes several papaya fruit set in a cluster, instead of
only a single fruit at each node. Unless the fruit is of small
size there is likely to be some damage resulting from crowding
with some fruit broken off by its own weight when another
offers leverage. Control of insects is more difficult also when
fruit is crowded, and many fruit may be deformed by pressure.
Under such conditions it will probably pay to thin the clusters
of fruit, leaving not more than two at a node, or even a single
fruit only when they are above 4 or 5 pounds weight at ma-
turity. The sooner this is done after the fruit is set, the better.

PICKING, PACKING AND SHIPPING
The papaya fruit usually turns yellow at maturity, the imma-
ture fruits being a dark green color. Fruit for shipping should
be picked when distinct traces or streaks of yellow color are
visible. At this stage fruit will ripen with practically as good
flavor as will fruit allowed to mature fully on the plant, and
it will still carry for several days before becoming soft. Fruit
wanted for local consumption should be left for one or two
days longer than fruit for shipping, but should rarely be left
on the tree until full yellow color has developed. Such fully






Papaya Culture in Florida


ripened fruit is not only hard to handle for even local markets,
but is likely to suffer damage from attacks by birds and wasps,
and may fall from the tree because of the ease with which the
fruit stem pulls out of the fruit at full ripeness.
Not all varieties develop yellow streaks as indications of in-
cipient ripening, and some do not even become yellow at full
maturity. The Betty variety indicates the harvesting condition
by development of a bronze color around the apex of the fruit.
Familiarity with the characteristic maturing behavior of each
variety is essential in order to be sure of recognizing the stage
of maturity suited to harvesting with best results.
Great care must be exercised in picking and handling the
fruit, as the skin is very thin and easily injured. Buckets or
field boxes used in harvesting the fruit should be padded or
lined. Exeelsior or hay covered with paper, or burlap alone,
makes satisfactory lining for fruit containers. Truck bodies
used for hauling papayas in bulk need similar protection.
Since the papaya fruit has a skin which bruises easily, harsh
packing materials must be avoided. "The fruits may be wrapped
in one or two thicknesses of newspaper or packed with shredded
paper. The avocado lug is a good container for smaller sizes
of fruit, and the quarter box for the larger ones. Containers
should hold only one layer of fruit, as the weight of an upper
layer is likely to crush a lower one somewhat. | Containers of
corrugated fibre board, with partitions between the individual
fruits, have been especially satisfactory, since papayas cannot be
packed with any degree of pressure on the fruit, such as com-
mon bulge packs of tomatoes or citrus fruits entail.

Cold storage of papayas has not proven very satisfactory. In
some cases fruit fully colored but still firm has been found
by Wardlaw and his colleagues in Trinidad (22) to remain in
good condition for two weeks at 450 F., and to ripen properly
thereafter on removal to ordinary room temperature. In other
cases this was not so. Fruit just beginning to show color, or
fully green still, was not stored with success at any temperature
between 300 and 600 F. At lower temperatures than 50' F.,
the chilling of the fruit prevented proper ripening later, while
at higher temperatures the loss from fruit diseases became
excessive in a few days..






Florida Agricultural Experiment Station


YIELDS AND RETURNS
The papaya tree bears enormous crops under optimum condi-
tions. It is not exceptional for trees to have 50 fruit at one time,
ranging from full grown to very small, and new fruits are con-
tinually produced over a period of many months. Such fav-
ored trees may bear 300 pounds of mature fruit during a pro-
ducing life of 15 months. However, for normal expectation
in a commercial planting, an average yield of 20 to 40 fruits
during a bearing life of 12 to 18 months is a reasonable estimate
if the planting is well cared for and has favorable weather con-
ditions. The average yield on a weight basis would probably
be from 75 to 150 pounds per tree.
The size of the fruit varies with the type or variety, and ranges
from the 1 pound Solo variety to the 15 or 20 pound fruit of some
Cuban types. In geral smaller sizes are preferred for
the fresh fruit trade, and the larger sizes or processing plants.
i Fruit of rom 2 to 4 poun s weight, wi attractive yellow skin
color and an orange or red flesh color if possible, and with good
flavor is most desirable for sale as fresh fruit. Such small size
fruit packs and ships better than the larger and heavier fruit.
Even in these small sizes, a thick flesh is highly desirable.
Returns on fresh fruit are largely proportional to the energy
expended in contacting consumer markets. The highly perish-
able nature of the fruit does not make it well adapted to the
usual consignment of shipments to brokers. The successful
shipper usually has contacted markets among hotels, restaurants
and fancy fruit stores and makes regular shipments. The bulk
of the fresh fruit is sold locally, however, or at least within
the state.
In the last few years a large market has developed within the
state for fruit to be processed in various ways, as discussed
under another section of this bulletin. The outlet thus made
available is far larger than that for fruit to be consumed fresh,
and plantings have been increased greatly to supply this mar-
ket. In consequence of the relative newness of this market, and
the influence of imported Cuban fruit on the price paid at pro-
cessing plants, returns have fluctuated widely.

DEVELOPING NEW VARIETIES AND SEED SELECTION
There are very few varieties of papaya, in the sense in which
the horticulturist uses the word "variety." Most so-called va-
rieties are somewhat indefinite types, with considerable vari-






Florida Agricultural Experiment Station


YIELDS AND RETURNS
The papaya tree bears enormous crops under optimum condi-
tions. It is not exceptional for trees to have 50 fruit at one time,
ranging from full grown to very small, and new fruits are con-
tinually produced over a period of many months. Such fav-
ored trees may bear 300 pounds of mature fruit during a pro-
ducing life of 15 months. However, for normal expectation
in a commercial planting, an average yield of 20 to 40 fruits
during a bearing life of 12 to 18 months is a reasonable estimate
if the planting is well cared for and has favorable weather con-
ditions. The average yield on a weight basis would probably
be from 75 to 150 pounds per tree.
The size of the fruit varies with the type or variety, and ranges
from the 1 pound Solo variety to the 15 or 20 pound fruit of some
Cuban types. In geral smaller sizes are preferred for
the fresh fruit trade, and the larger sizes or processing plants.
i Fruit of rom 2 to 4 poun s weight, wi attractive yellow skin
color and an orange or red flesh color if possible, and with good
flavor is most desirable for sale as fresh fruit. Such small size
fruit packs and ships better than the larger and heavier fruit.
Even in these small sizes, a thick flesh is highly desirable.
Returns on fresh fruit are largely proportional to the energy
expended in contacting consumer markets. The highly perish-
able nature of the fruit does not make it well adapted to the
usual consignment of shipments to brokers. The successful
shipper usually has contacted markets among hotels, restaurants
and fancy fruit stores and makes regular shipments. The bulk
of the fresh fruit is sold locally, however, or at least within
the state.
In the last few years a large market has developed within the
state for fruit to be processed in various ways, as discussed
under another section of this bulletin. The outlet thus made
available is far larger than that for fruit to be consumed fresh,
and plantings have been increased greatly to supply this mar-
ket. In consequence of the relative newness of this market, and
the influence of imported Cuban fruit on the price paid at pro-
cessing plants, returns have fluctuated widely.

DEVELOPING NEW VARIETIES AND SEED SELECTION
There are very few varieties of papaya, in the sense in which
the horticulturist uses the word "variety." Most so-called va-
rieties are somewhat indefinite types, with considerable vari-






Papaya Culture in Florida


ation exhibited in seedlings from a single fruit. Until several
fairly pure lines have been segregated, there is not much op-
portunity for breeding by recombination of characters, but a
great deal can be done by growers who wish to practice mass
selection. At present it is difficult to obtain a quantity of seed
of known quality and uniformity, although one or two fairly
reliable varieties are commercially available.
The grower who wishes to save seed for his own use should
keep in mind certain principles. Seed should be saved only from
plants which have carried a heavy crop of fruit of desirable
size, shape and flavor. If the plant produces perfect flowers,
i. e., is a bisexual type, several of these flowers should be bagged
before they open, to prevent any chance of pollination from
another plant. Usually these bagged flowers will set fruit, but
if the first flowers do not set any, it may be necessary to hand
pollinate some later ones. The bag is removed after the flower
opens its petals, and pollen from one of its own stamens is dusted
onto the large expanded stigma which surmounts the "fruit"
or ovary. Glassine bags are very satisfactory, because they
enable the grower to see when the flower opens. After the
flower is pollinated the bag should be replaced and kept there
until the petals wither. Identification tags should be attached
to the flower stalk at the time the flowers are bagged. Large
scale seed producers may find it desirable to bag flowers from
the beginning of flower production, bagging them on a great
many plants and discarding the tags on plants which later prove
to have fruit of undesirable character. Until some progress
has been made toward segregation of a definite type, however,
it is more satisfactory to wait until the first fruits mature be-
fore selecting plants for seed production. The long bearing
life of the papaya makes this easily possible, and a very few
fruits will provide many hundred seeds for further trial and se-
lection.
If the plant selected has only pistillate flowers, i. e., is
a female tree, then the only possible course is to select pollen
from some vigorous male plant produced from the same original
fruit as the female plant selected. If that cannot be done, a male
must be chosen at random, and in succeeding generations can
be selected as above. Of course the female flower should be
bagged and tagged before the petals open, and the bag removed
only long enough to dust pollen onto the stigma. When the
petals have withered there is no longer chance of pollination
from any unknown source.






Florida Agricultural Experiment Station


In either of the above cases there will be considerable variation
from the parent fruit type, except in the case of varieties already
selected on this basis for some generations, but there will be
less variation than if these precautions had not been taken. If
from these selected seeds the best seedlings are again selected
the next year in the same way, it will be possible in a few years
to build up a type which will be fairly free from undesirable
variations and may properly be considered a variety. It is not
possible to increase the absolute quality of this type by selection,
but it is possible to eliminate most of the variation from that
type. Likewise it is usually possible to increase greatly the pro-
portion of bisexual progeny in a line which produces bisexual,
male and female forms, by constant selection of bisexual forms

















Fig. 13.-Small fruit (6 inches long) of bisexual type. Note small seed
cavity.

and self-pollinating them. If quality can be selected at the same
time, i. e., if bisexual types of the best quality are available
for selection, it is the opinion of most of those who have studied
the question carefully that the bisexual type is the ideal one.
It eliminates the problem of the selection of males in dioecious
types, and it permits both greater simplicity of self-pollinating
(since mere bagging often does this) and a greater proportion
of fruiting plants from the seedlings raised. Present information
indicates that it is not possible to have a bisexual variety which
will reproduce entirely true to sex type, but a very high percent-
age of bisexual progeny can be secured with the balance al-
most wholly females.






Papaya Culture in Florida


It cannot be too strongly impressed on the prospective papaya
grower that he must strive always for certain definite fruit
characteristics: small, compact size and high quality flavor for
the fresh fruit market, and large size and quantity of production
for the processing market. The most desirable physical type for
the fresh fruit trade is one with relatively thick flesh and a
small seed cavity, not over half the body diameter (Fig. 13),
but many types of good flavor will be worth growing in spite of
a large seed cavity (Fig. 14). The grower who does not wish
to attempt to save his own seed should be very careful about the
seed he buys, inquiring carefully into the manner in which


Fig. 14.-Small fruit (6 inches long) of pistillate type. Note large
seed cavity.

it was produced and the qualities of the parent type. If it is
only seed from large fruits, or even from large fruits of heavy
yielding plants, he may better save his own. If the seed has
come from self-pollination in a type selected over several years,
and the qualities of that type are fairly uniform, then he may
buy confidently. The cost of growing plants which bear poor
fruit is just as great as that for good fruit, and the grower
cannot afford growing any but the good. The cost of good
seed is the smallest cost in growing papayas, even though the
seed seems expensive on a pound basis.






30 Florida Agricultural Experiment Station

Seed may be stored for a year or more without appreciable
loss of viability if care is taken to keep it dry and cool. The
greatest handicap to seed storage in warm countries is the high
humidity, assuming that care is taken to prevent insect infesta-
tion. After the seed is removed from the fruit and washed,
it should be thoroughly dried by spreading on paper in a shaded
place with good ventilation. The well dried seed can be stored in
glass jars with tightly sealed tops, covered with paraffin if
closed by corks but not if sealed by rubber gaskets. A dry day
should be chosen for putting seeds in the jars.

DISEASES
In Florida there are only two important fungous diseases of
papayas, although several other minor diseases are some-
times found. These important diseases are a leaf spot and a
fruit rot. Stevens (17) has recently summarized our meagre
knowledge of the control of these diseases, on which much
research is yet to be done.
Leaf Spot.-This disease is caused by the fungus Pucciniopsis
caricae Earle. Spots are usually circular, about Vs inch in di-
ameter, and limited to mature leaves. The upper surface of the leaf
shows these spots first as pale or yellowish and finally as brown
areas of dead tissue, while on the lower surface they appear black
and slightly raised, owing to masses of black fruiting bodies. The
spores produced from them rapidly spread the disease over the
surface of the infected leaf and of other leaves. Severely in-
fected leaves are able to do very little work, and usually they
are killed completely and drop from the tree. The disease is
usually most serious during the dry, cool seasons of winter and
spring, when a large proportion of the mature leaves may be
killed.
Infection occurs only on mature (fully expanded) leaves and
only on the under side of the leaf. Stevens (17) states that if
the infected leaves are kept removed, three or four applications
of 3-3-50 bordeaux mixture to the under surface of the mature
leaves at intervals of two weeks should serve to clean up a mod-
erate infection. Under conditions that favor vigorous growth,
the papaya leaves appear to resist the attack of this disease fairly
well, and unsprayed plants may then suffer no more damage
than sprayed ones.
Fruit Rot.-This disease is caused by a species of Colletotrichum,
either the same as or very closely related to the species (C.






Papaya Culture in Florida 31

gleosporioides Penz.) which causes the rots of so many tropical
fruits, such as black spot of avocados and mangos. Appearing
first as small, dark, sunken areas on the rind of the full grown
fruit, the spots develop rapidly as the fruit matures, until a
decayed area as large as a silver dollar may result. After picking,
the fruit decay spreads rapidly, so that a whole side of the fruit
may be unfit for consumption by the time the fruit is soft enough
to eat.
According to Wardlaw et al (21) the fungus can infect the
papaya fruit at any stage of its development, so that there is
no critical period in which to concentrate efforts at protection.
Sanitary measures seem to give better control than spraying.
Infected fruits should be removed as soon as infection is evident.
and fruits showing no infection should be picked before they de-
velop full yellow color. Such fruit usually has early stages of
infection and will become a source of further infection if allowed
to ripen on the tree, since the spores can be carried by wind and
water. Infected fruits and all dead papaya tissue should not only
be removed from the tree but should be burned or buried deeply
to prevent their infecting other fruit.
Powdery Mildew.-This disease, caused by a species of Oidium,
is characterized by the presence of a white, cobwebby growth
over both the upper and lower surfaces of irregular leaf spots.
Powdery spore masses develop on the mildewed areas. The
infected leaves soon turn yellow, the tissue dies, and the leaves
drop. The disease may cause considerable injury in a few weeks,
but is easily controlled by dusting with sulfur. Two or three
applications at 10-day intervals should suffice. Infection occurs
only on mature leaves and is usually most serious in winter and
spring.
INSECTS
Papaya Fruit Fly.-This insect was introduced into Florida
about 1905, and ever since has been a constant hazard of papaya
growing. Fortunately it can be controlled fairly readily. It is
called Toxotrypana curvicauda.
This fruit fly is about half an inch long, and looks like a small
wasp. The female has an ovipositor as long as her body proper.
By means of this appendage eggs are laid in the cavity of the
fruit, the ovipositor penetrating the whole thickness of the flesh.
While fruit at least half grown is preferred, the fly may lay
eggs in any size of fruit available, from newly set fruit on up.






Florida Agricultural Experiment Station


The eggs hatch into larvae which usually feed on the seeds and
the lining of the seed cavity until the flesh begins to soften
(Fig. 15). Then they generally eat their way out through the
flesh and skin, and drop to the ground for pupation in the soil.


Fig. 15.-Young papaya fruit (3 inches long) showing some tunneling
in hard, immature flesh by larvae of the papaya fruit fly. Usually the
larvae feed only on the seeds and their arils until the flesh softens.

Thick fleshed varieties are less subject to attack than thin
fleshed ones, since the eggs cannot develop when the flesh
is too thick to permit the ovipositor to penetrate to the seed
cavity. Of course the very young fruits of the varieties with
thickest flesh can still be attacked, but fruits half grown or
larger will usually be immune. The larvae are able to attack
the flesh of the green fruit without injury to themselves.
However, they do not like to do this and usually leave it alone
until near maturity.

Sanitation is an important item in control of this fruit fly.
By picking up and destroying all dropped fruits or fruits on
the tree which turn yellow prematurely, and by destroying also
small fruits on the trees which show sting scars and contain
discolored areas indicating that eggs have been laid and larvae






Papaya Culture in Florida


are developing, the flies will be prevented from completing their
life cycle. In the back yard papaya patch, this care may be
frustrated by a neighbor's carelessness, so that community co-
operation is important. The commercial grower should destroy
all possible wild papaya plants within a mile or two of his
planting.
The final measure of protection is the use of poison sprays.
The adults feed eagerly on brown sugar syrup, in which an
arsenical compound can be incorporated, as Mason (11) pointed
out. The poison bait used for the Mediterranean fruit fly
may be used, taking care to apply it only as a fine mist and
not allowing it to accumulate on the leaves until it drips. The
foliage is easily burned by this spray if it forms large drops
of liquid. The formula is:
1/ pound brown sugar
1 pint blackstrap molasses
1 ounce lead arsenate
2 gallons of water.
It should be applied once or twice a week, so long as fruit
flies are found, and should be applied to the fruit and trunk
rather than to the leaves. The poison bait may also be placed
in small containers hung from the leaf stalks of the papaya
plants and replenished every week or so. This method gives
less complete protection but avoids foliage burn.
Papaya Webworm. In recent years a small caterpillar,
Homolapalpia dalera, somewhat like the cucumber pickle worm,
has caused much damage to papaya plantings. It forms a small
web over the junction of the fruit stem with the trunk or
with the fruit itself, and under the protection of this web it
eats into the growing fruit or its stem. Spraying is difficult
because the web soon fills with excreta. A strong pyrethrum
spray, or a rotenone spray, gives fair control if applied with
enough pressure to drive away the web. A further help is
the use of a feather to brush out the webbing from the angle
where it is formed, thus giving the spray free access to the
fruit and stem surface. A lead arsenate spray, the usual
1 pound to 50 gallons, may be used also, but at least 4 pounds
,of hydrated lime should be added to prevent burning.
/ Nematodes.-The root-knot nematode, Heterodera marioni, fre-
quently attacks the roots of papaya plants, especially if they are
planted on soil which has previously been cropped to peppers,







Florida Agricultural Experiment Station


tomatoes, or other preferred hosts. Well fertilized and watered
papaya plants are able to bear fairly well in spite of the root-
knot attack, but plants infected in the seedbed are not likely to
develop into strong trees. Seedbed soil should be carefully
sterilized, unless it is virgin soil.' Heavy mulching is desirable
for field plants as a moisture conservation measure, and this
practice will also aid in keeping the root-knot organisms in
check. Newly cleared land will usually be free from nema-
todes, and old land can be freed from them by planting for a
season with cover crops which are immune to their attack,
while all other plants are kept out. (Refer to Florida Agricul-
tural Experiment Station Bul. 311.)
Whitefly.-Occasionally a heavy infestation occurs of the
papaya whitefly, Trialeuroides variabilis Quaint. This is often
recognized first by the sooty mold which develops in the honey-
dew secreted by the whitefly, making the leaves and stem black.
The watchful grower will detect the beginning of the infestation
on the tender new leaves at the top of the plant. ( Heavily in-
fested leaves may turn yellow and drop, and the black coating
cuts down the ability of the green tissues to make food. A
pyrethrum spray gives control if the pyrethrin content is good.
Regular dusting with sulfur once a week will keep the whitefly
out also, and usually two or three weekly applications will con-
trol an infestation which has started. Oil sprays are very ef-
fective, but only the highest grade of summer oil is safe to use.

Red Spider.-During the long periods of dry weather, the red
spider mite, Tetranychus seximaculatus, frequently attacks the foli-
age of papaya plants. This mite sucks the juice from the leaves,
giving them a bronzed appearance and reducing their efficiency.
Sulfur dust is the easiest and quickest method of control.

LITERATURE CITED
1. Atwood, Geo. W. The fruits of Florida. Rept. U. S. D. A. 1867:
140-147. 1868.
2. Bartram, Wm. Travels through North and South Carolina, Georgia
and Florida. Part II, p. 129. 1791.
3. Blanco, M. Flora de Filipinas. Ed. 1, p. 205. 1837.
4. Ellis, W. Polynesian researches during a residence of nearly
eight years in the Society and Sandwich Islands. 1859. (Cited by Pope.)
5. Forster, George. A voyage around the world (1772-1775). 1777.
6. Higgins, J. E., and V. Holt. The papaya in Hawaii. Hawaii Agr. Exp.
Sta. Bull. 32. 1914.
7. Hofmeyer, J. D. J. Determination of sex in Carica papaya. Farming
in South Africa 13: 332. 1938.








Papaya Culture in Florida 35

8. Linschoten, J. H. van. Itinerarium ofte Schipvaert naar Oost ofte
Portugaels Indien. Vol. I, p. 224. 1596.
9. Lynch, S. J., and W. M. Fifield. Some chemical constituents of
papaya and their relation to flavor. Proc. Fla. State Hort. Soc. 53: 181-
184. 1940.
10. Maloney, W. C. A few facts from Florida-the "Keys." Rept.
U. S. D. A. 1871: 164-165. 1872.
11. Mason, A. C. Biology of the papaya fruit fly, Toxotrypana
curvicauda, in Florida. U. S. D. A. Bul. 1081. 1922.
12. Oviedo, G. H. de. Historia general y natural de las Indias. 1535.
13. Pope, W. T. Papaya culture in Hawaii. Hawaii Agr. Exp. Sta.
Bull. 61. 1930.
16. Reasoner, P. W., and W. G. Klee. Report on the condition of
tropical and subtropical fruits in the United States in 1887. U. S. D. A.
Div. of Pomology Bul. 1: 21-22. 1891.
15. Robertson, J. A. The true relation of the Hidalgo of Alvas,
1557, pp. 19, 20.
16. Solms-Laubach, H. Die Heimath und die Ursprung des culti-
vierten Melonenbaumes, Carica papaya L. Bot. Ziet. 47: 709-798. 1889.
17. Stevens, H. E. Papaya diseases. Proc. Fla. State Hort. Soc. 52:
57-63, 1939.
18. Stickney, L. D. Tropical Florida. Rept. U. S. D. A. 1861:
402-404. 1862.
19. Storey, W. B. The primary flower types of papaya and the
fruit types that develop from them. Proc. Amer. Soc. Hort. Sci. 35:
80-82. 1937.
20. Storey, W. B. Segregations of sex types in Solo papaya and
their application to the selection of seed. Proc. Amer. Soc. Hort.
Sci. 35: 83-85. 1937.
21. Wardlaw, C. W., R. E. D. Baker and S. H. Crowdy. Latent in-
fections in tropical fruits. Trop. Agri. (Trinidad) 16: 275-276. 1939.
22. Wardlaw, C. W., E. R. Leonard and R. E. D. Baker. Observations
on the storage of various fruits and vegetables. Part II. Trop. Agric.
(Trinidad) 11: 230-235. 1934.




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