Title: Papaya culture in Florida
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 Material Information
Title: Papaya culture in Florida
Alternate Title: Bulletin 113 ; Florida Agricultural Extension Service
Physical Description: Book
Language: English
Creator: Wolfe, Herbert S.
Lynch, S. J.
Publisher: Agricultural Extension Service, University of Florida
Publication Date: June, 1942
Copyright Date: 1942
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Bibliographic ID: UF00026332
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: aab7720 - LTQF
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002571114 - AlephBibNum

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




Bulletin 113



L3!
: 3/3


June, 1942


PAPAYA CULTURE EENT OF AGRI
LIBRARY

IN FLORIDA* JUN6 1950

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AGRICULTURAL EXTENSION SERVICE
GAINESVILLE, FLORIDA
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COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLORIDA
FLORIDA STATE UNIVERSITY
AND UNITED STATES DEPARTMENT OF AGRICULTURE
COOPERATING
H. G. CLAYTON, Director
BOARD OF CONTROL
Frank M. Harris, Chairman, St. Petersburg
N. B. Jordan, Quincy
Hollis Rinehart, Miami
Eli H. Fink, Jacksonville
George J. White, Sr., Mount Dora
W. F. Powers, Secretary, Tallahassee
STAFF, AGRICULTURAL EXTENSION SERVICE
J. Hillis Miller, Ph.D., President of the University'
J. Wayne Reitz. Ph.D., Provost for Agriculture
H. G. Clayton, M.S.A., Director of Extension
Marshall O. Watkins, M.Agr., Assistant to the Director
AGRICULTURAL DEMONSTRATION WORK, GAINESVILLE
J. Francis Cooper, M.S.A., Editor'
Clyde Beale, A.B.J., Associate Editor'
J. Lee Smith, District Agent
K. S. McMullen, B.S.A., District Agent
F. S. Perry, B.S.A., District Agent
H. S. McLendon, B.A., Soil Conservationist
R. S. Dennis, B.S.A., Executive Officer, P. & M. Admin.'
W. W. Brown, B.S.A., Asst. Boys' Club Agent
C. W. Reaves, B.S.A., Dairy Husbandman
N. R. Mehrhof, M.Agr., Poultry Husbandman'
O. F. Goen, D.V.M., Asst. Animal Industrialist
A. W. O'Steen, B.S.A., Supervisor Egg-Laying Test, Chipley
L. T. Nieland, Farm Forester
C. V. Noble, Ph.D., Agricultural Economist'
Charles M. Hampson, M.S., Agricultural Economist, Farm Management
D. E. Timmons, M.S.A., Economist in Marketing
F. W. Parvin, B.S.A., Associate Economist, Marketing and Farm Manage-
ment
John M. Johnson, B.S.A., Agricultural Engineer
Fred P. Lawrence, B.S.A., Citriculturist
A. M. Pettis, B.S.A., Farm Electrification Specialist'
John D. Haynie, B.S.A., Apiculturist
V. L. Johnson, Rodent Control Specialist'
J. Russell Henderson, M.S.A., Agronomist'
F. S. Jamison, Ph.D., Vegetable Crop Specialist'
Stanley E. Rosenberger, M.Agr., Asst. Veg. Crop Specialist
HOME DEMONSTRATION WORK, TALLAHASSEE
Mary E. Keown, M.S., State Agent
Ethyl Holloway, B.S., District Agent
Mrs. Edith Y. Barrus, B.S.H.E., District Agent
Anna Mae Sikes, M.S., District Agent
Joyce Bevis, A.M., Clothing Specialist
Mrs. Bonnie J. Carter, B.S., Home Improvement Specialist
Grace I. Neely, M.S., Asso. Economist in Food Conservation
Lorene Stevens, B.S., State Girls' 4-H Club Agent
Mrs. Gladys Kendall, A.B., Home Industries and Marketing Specialist
NEGRO EXTENSION WORK, TALLAHASSEE
Floy Britt, B.S.H.E., Negro Home Demonstration District Agent
J. A. Gresham, B.S.A., Negro District Agent
SCooperative, other divisions, U. of F.
2 In cooperation with U. S.











PAPAYA CULTURE IN FLORIDA

By H. S. WOLFE1 and S. J. LYNCH2
CONTENTS
Page Page
History -...--......-.... .. ..-. ..- ...- 3 Mulching and Irrigation .......... ...... 21
Botanical Relationships ..... ......... 4 Thinning of Fruit ........- 22
Uses ....~.--..-.. _--... -....-.- .- ... 4 Picking, Packing and Shipping ----... 22
Flower Structure and Sex Variations... 6 Yields and Returns -.._- ----...-.... -- 23
Climate and Soil _. .-- -.. --.__..__ 15 Seed Selection _-..--..... -.- 24
Propagation -..-........- .. ...- ...... .... 16 Fungous Diseases -....-...- ..... .-.. - 28
Planting .. ---...........--- ......-. .......... 19 Animal Pests _.........---.... -- .--~. ..... 29
Fertilization ....... ........ .....-... ...- .. 21

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.
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

1 Formerly Horticulturist in Charge, Sub-Tropical Experiment Station
Now Head, Department of Horticulture, College of Agriculture.
2 Formerly Associate Horticulturist, Sub-Tropical Experiment Station.








Florida Agricultural Extension Service


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 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.
BOTANICAL RELATIONSHIPS
The papaya is known to botanists as Carica papaya L. Original-
ly assigned to the Passion-flower family, it has long since been
made the type of the family Caricaceae.
The papaya plant is really a gigantic herb, rather than a tree,
since it never develops a typical woody stem. Usually the trunk
is 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 to 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,
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
presence 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 contains any appreciable
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








Papaya Culture in Florida


90%) and contains very little actual nourishment. Sugar con-
tent of Florida papayas has been found to vary from about 4
to 10 percent of the fresh weight of the pulp. Papayas are
a very good source of vitamin A, a good source of C, a fair source
of G, and contain a small amount of B1.
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 cantaloupes 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 high 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
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.
Production in Florida has increased considerably and except
in a few instances has been sufficient to meet demands 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 temporarily
curtailed. However, the fresh fruit markets are supplied almost
entirely by Florida-grown fruit.







Florida Agricultural Extension Service


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 botannical descriptions so
indicated them. Seed of the bisexual type of papaya was first
sent to Hawaii from Ceylon in 1896, 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


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

summary of the view of the workers at the Hawaii Experiment
Station will be followed as a basis for discussion. Five basic
flower types are recognized, as follows:
TYPE 1.- "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
fruit shows five separate scars where the petals fell off. The
flowers are large, from 2 to 21,j inches long, and borne either








Papaya Culture in Florida


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 oc-
curred and growth begun. The matured fruit may weigh
anywhere from 12 ounces to 12 pounds, usually from 2 to 5
pounds. It varies in shape from somewhat spherical to oblong
or pyriform, but usually has a body cavity which is large in
comparison with the thickness of the walls and is more than
half the diameter of the whole fruit (Figs. 3, 4, 12).


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

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 fila-








Florida Agricultural Extension Service


ments which lie in deep grooves in the ovary wall. These
grooves persist in the mature fruit, which is rounded but deep-
ly five-lobed. The fruit of the pentandria flowers is very char-
acteristic and unmistakable.


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

TYPE III.-Intermediate type. This is not a single and defi-
nite type,, but is rather a group in which are included many
abnormalities 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 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 side of the pistil open. Fruit from such de-
fective 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








Papaya Culture in Florida


elongated and subcylindrical, in contrast with the more round-
ed form of the female type. In the usual bisexual form the
flowers are borne in short cymose clusters, from 3 to 5 inches
long on stout peduncles, the individual flowers being from 11/2
to 2 inches 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. Five stamens are alternate with the petals

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


:'ry 7- =








Florida Agricultural Extension Service


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

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 function-
al. The filaments are united into a ring adnate to the corolla








Papaya Culture in Florida


tube, making a thick collar around the pistil. The pistil is
composed of five carpels usually, and has sessile upon it the five
stigmas as in Type I. 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 tube compressed it, and expanding
somewhat at the upper end, but variations in form from pyri-


















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

form to cylindrical are found. The typical bisexual fruit is 10
to 12 inches long, nearly half that thick, and weighs from 6 to 8
pounds (Figs. 6 and 7), but much smaller-fruited types have
been selected (Fig. 11). Usually the cavity is less than half
the fruit diameter.
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 poor-
ly developed stigmas, or pentandria type.
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. The flowers are much smaller, being
only about half the size of the perfect flowers on the bisexual type
plants, but they are otherwise similar in structure and function.







Florida Agricultural Extension Service


TYPE V.-"Male" or staminate flowers (Fig. 8). These flowers
are characterized at once by their lack of any stigmas and by
the great length and slenderness of the corolla tube, which is
twice as long as the free corolla lobes or petals. There are 10
stamens, arranged as in the Type IV flower, but the pistil is re-


Fig. 7.


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


duced to a mere rudiment, with no stigma and incapable of func-
tioning. Consequently the staminate flowers cannot produce
fruit.
On male trees the flowers are produced in small clusters
which are in turn borne on long pendant peduncles in racemose
form (Fig 9). Staminate flowers appear also in the short cymose








Papaya Culture in Florida


clusters on bisexual trees. The staminate flowers of male trees
produce potent pollen, but Higgins and Holt reported the pollen
from staminate flowers on bisexual plants as unable to cause fruit
to set with any type of flower tried. However, Hofmeyer reported
obtaining fruit and seed repeatedly from pollination with these
flowers.
















Fig. 8.-Staminate flower cluster and individual flowers. Note
rudimentary pistil in middle flower, cut open.

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







Florida Agricultural Extension Service


have a perfect pistil, so that they are really of Type IV, although
they are borne on the same long peduncles as the staminate flow-
ers and are much smaller than the usual hermaphrodite flowers.
Such trees may bear a considerable quantity of fruit (Fig. 9), al-
though 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 farther north, than in a more nearly tropi-
cal location .


Fig. 9.-Male papaya tree with several fruits developed from perfect
flowers on tips of the old inflorescences 10 months from seed.







Papaya Culture in Florida


In particular there have been misconceptions regarding the
relation of the fruiting of male trees to previous severe pruning.
Experiments at the Florida Station have confirmed those re-
ported from Hawaii as to the lack of any predictable effect
on the flower type from cutting back male trees. Rare instances
have been reported of male trees which produced only pistillate
flowers after severe pruning of the top, but in many other in-
stances 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 and South Africa, research workers have
developed fairly pure lines of papaya for study of genetic be-
havior. 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 67% bisexual, with the bal-
ance female.
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 can endure light frosts if the plants are
not too tender, but it prefers and thrives best under frostless con-
ditions. Successful cultivation of the papaya can be expected
only along the lower East and West Coasts of Florida, and per-
haps in a few localities in the lower Ridge section where air drain-
age is usually 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








Florida Agricultural Extension Service


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 pa-
payas were badly injured by frost.
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.
The papaya can thrive on almost any type of soil, providing
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 vig-
orously but the fruit is often of poor flavor. On muck soil of the
Everglades growth is phenomenal and tremendous crops are pro-
duced, but quality is 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 practical 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 of cuttings
available is always very small, owing to the non-branching habit
of the papaya. It is possible, also to graft from particularly fine
plants on seedling stocks, but the type runs out soon and propa-
gating material is very 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
bearing 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








Papaya Culture in Florida


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 from one
to three weeks sooner than by the usual transplanting.
Bottomless cups made of 15-pound asphalt felt paper have
proven quite successful for use as community pots. The cost of
the materials is less than 1/2 cent per cup, and the labor required
is very little. A roll of paper is sawed into five 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 dia-
meter. 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 pushed 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 com-
munity pot should be planted three or four seeds of a bisexual
type of papaya or seven or eight seeds of a unisexual type, spac-
ing 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.
Small papaya seedlings are subject to damping-off, and the
soil for the pots or flats should be sterilized if possible. Steril-
ization 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 sim-
plest 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







Florida Agricultural Extension Service


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 2 to 3
months from planting. (Fig. 10). At this time the plants in each
community pot should be thinned by removal of the weaker
seedlings, leaving two 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.
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
in 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 sys-
tem as possible. Pots should be at least the 3-inch size, and
cans of similar diameter, with holes in the bottom for drainage.















Fig. 10.-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


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
2 feet high, if grown in large enough containers or in deep
seedbeds, but it is not a desirable practice to allow them to be-
come 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 grow-
ing conditions-for developing to the fruiting stage. The first
fruit will probably mature in November, or perhaps in October,
from January seeding, and the mature plants will bear all win-
ter and 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 the papaya 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 1 foot and a width of 2 feet in sandy
soil. On the rocky soil of southern Dade County it will be ad-
vantageous 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 is avail-
able 5 pounds of high grade fish tankage or guano is recom-
mended 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. Felt
paper pots can be set at the proper soil depth and the paper re-
moved 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







Florida Agricultural Extension Service


if the soil and plants are to be set without disturbance. Where in-
dividual 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 remain
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. A 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, 2 inches apart. When these reach blooming age, so that
their sex can be distinguished, males or weak females can be re-
moved, leaving the bearing plants in place. This will assure the
presence of at least 1 female in 95%" of the hills. In rare in-
stances where no vigorous female is present in a hill, one can be
transplanted from a hill with excess strong females. In such case
it is important to observe the precautions indicated above for
plants left too long in the nursery row. Similarly, in cases of
bisexual types it is well to set two plants in each hill, to allow for
removal of off-type or weak plants at blooming. It will be ob-
served that plants grown in community pots will already have the
proper number for a hill in each pot. To assure pollination in
plantings of the unisexual type, at least 1 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 at fruiting.








Papaya Culture in Florida


FERTILIZATION
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 6 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-
tinuing 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 8% 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, although quality may not be equal.
After plants have set fruit, the organic materials should be
supplemented by an 0-10-10 fertilizer applied at the rate of /
pound per tree each month.
Excellent results have been obtained by many growers by using
commercial mixed fertilizers from the start. Beginning a couple
of weeks after the plants are set in the field, a 4-8-5 mixture is
used, with at least 25 % of the nitrogen from organic sources and
containing 3 units of available MgO. This should be applied bi-
weekly, starting with 1/ pound per hill and increasing gradually
until by the end of six months the rate is 1/2 pound. This rate is
continued so long as yields warrant keeping the plants in produc-
tion. If yellowish green foliage shows that plants are not getting
enough nitrogen, an extra application of 1/ pound of nitrate of
soda may be made. Consecutive applications of fertilizer should
not be made if there is no rain between them, unless irrigation is
used.
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 kept in active and vigorous growth
at all times, if its culture is to be successful. For this end,








Florida Agricultural Extension Service


regular and frequent applications of fertilizer are not sufficient.
The plants need a heavy mulch of grass, peat moss, sawdust
or some other material which will conserve moisture and pro-
tect the soil from over-heating 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. When papayas are grown on a
larger commercial scale careful consideration should be given to
irrigation facilities. Successful papaya culture requires an
abundant supply of water for the plants. Once checked in their
growth, papaya trees never recover satisfactorily.

THINNING OF 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 four or five pounds weight at maturity.
The sooner this is done after 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 ripened
fruit is not only hard to handle, even for 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








Papaya Culture in Florida


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. Excelsior 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 the 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
common 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 to remain in good
condition for two weeks at 45' F., and to ripen properly there-
after 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 be-
tween 30 and 60 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.

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 fully grown to very small, and new fruits are con-
tinually produced over a period of many months. Such favored
trees may bear 300 pounds of mature fruit during a producing
life of 15 months. However, for normal expectation in a com-
mercial planting, an average yield of 20 to 40 fruits during a








Florida Agricultural Extension Service


bearing life of 12 to 18 months is a reasonable estimate if the
planting is well cared for and has favorable weather conditions.
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 general the smaller sizes are preferred
for the fresh fruit trade, and the larger sizes for processing
plants. Fruit of from two to four pounds weight, with 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 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. Most fresh
fruit is sold locally, or at least within the state.
In the past 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-
ation exhibited in seedlings from a single fruit. Until several
fairly pure lines have been segregated, there is not much oppor-
tunity for breeding by recombination of characters, but a great
deal can be done by growers who wish to practice mass selec-
tion. 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







Papaya Culture in Florida


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 these 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 expended 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 selection.
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.
In either of the above cases there will be considerable varia-
tion 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








Florida Agricultural Extension Service


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 possible to increase greatly the proportion
of bisexual progeny in a line which produces bisexual, male
and female forms, by constant selection of bisexual forms 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
















Fig. 11.-Small fruit (6 inches long) of bisexual type. Note small
seed cavity.

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 elimination of non-
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 about 67 percent of
bisexual progeny can be secured with the balance wholly females.
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. 11),








Papaya Culture in Florida


but many types of good flavor will be worth growing in spite of
a large seed cavity (Fig. 12). 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
it was produced and the qualities of the parent type. If it is




















Fig. 12.-Small fruit (6 inches long) of pistillate type. Note large
seed cavity.

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 high 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. There are about 25,000
papaya seeds in a pound, or about 600 in one ounce.
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







Florida Agricultural Extension Service


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 jars.

FUNGOUS DISEASES
In Florida there are only a few important fungous diseases of
papayas, although several other minor diseases are sometimes
found. These important diseases include the common leaf spot,
fruit rots, and a leaf spot of unknown etiology which has become
widespread and destructive in South Florida since 1940. Very
recently papaya mosaic disease has been reported. In the West
Indies this is now widely spread and very destructive, and Florida
growers should be on the alert for it. The first symptoms are
water-soaked spots on petioles and mosaic of blades of very young
leaves. In a few weeks the whole crown dies, but lower buds
may develop into branches. Control consists in cutting off
infected tops as soon as possbile at least three feet below the tip.
Common Leaf Spot.-This disease is caused by the fungus
Pucciniopsis caricae Earle. Spots are usually circular, about 1/8
inch in diameter, and limited to mature leaves, but may also be
found on the fruit, where they may cause rots as the fruit ma-
tures. 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 infected 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 states that if infected
leaves are kept removed, three or four applications of 3-3-50
bordeaux mixture to the under surface of mature leaves at inter-
vals of two weeks should serve to clean up a moderate infection.
Under conditions that favor vigorous growth, papaya leaves
appear to resist attack of this disease fairly well, and unsprayed
plants may then suffer no more damage than sprayed ones.
Fruit Rots.-These are caused for the most part by a species







Papaya Culture in Florida


of Colletotrichum, either the same as or very closely related to
the species (C. gloeosporioides 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, 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 develop
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. Species of Diplodia,
Phomopsis and other fungi are responsible for some rotting of
fruit.
Powdery Mildew.-This disease, caused by species of Oidilm,
is characterized by a white, cobwebby growth over both upper
and lower surfaces of irregular leaf spots. Powdery spore masses
develop on the mildewed areas. Infected leaves soon turn yellow,
the tissue dies and the leaves drop. The disease may cause con-
siderable injury in a few weeks, but is easily controlled by dust-
ing 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.

ANIMAL PESTS
Papaya Fruit Fly.-This insect was introduced into Florida
about 1905, and ever since has been a constant hazard of papaya
growing. It cannot yet be controlled with certainty. 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 she lays eggs in the cavity of the







Florida Agricultural Extension Service


fruit, her 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.
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. 13). Then they generally eat their way out through the
flesh and skin, and drop to the ground for pupation in the soil.
Thick-fleshed varieties are less subject to attack than thin-
fleshed ones, since the eggs, cannot develop when the flesh is thick
enough to keep the ovipositor from penetrating to the seed cavity.
Of course young fruits of varieties with thickest flesh can still be
attacked, but fruits half grown or larger will usually be immune.
Larvae are able to attack the flesh of 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 stings and scars and contain



















!T-



Fig. 13.-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.







Papaya Culture in Florida


discolored areas indicating that eggs have been laid and larvae
are developing, the flies will be prevented from completing their
life cycle. In the backyard 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 wild papaya plants within a mile or two of his planting.
An added 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 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 control 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 spray of 2 pounds of 50 % wettable
chlordane or 1 pound wettable DDT per 100 gal. water gives good
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.
Nematodes.-The root-knot nematode, Heterodera marioni,
frequently attacks the roots of papaya plants, especially if they
are planted on soil which has previously been cropped to peppers,
tomatoes, or other preferred hosts. Well fertilized and watered
papaya plants are able to bear fairly well in spite of the root-








Florida Agricultural Extension Service


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 other plants are kept out. (Refer to Florida Agricultural
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. For
control spray with 8 pounds wettable sulfur per 100 gals. water
as soon as the adults are seen. Regular dusting with sulfur once
a week will keep the whitefly out also, and usually two or three
weekly applications will control an infestation which has started.
Oil sprays are very effective, but only the highest grade of sum-
mer oil is safe to use.
Red Spider.-During long periods of dry weather, the red
spider mite, Tetranychus seximaculatus, frequently attacks the
foliage of papaya plants. This mite sucks the juice from the
leaves, giving them a bronzed appearance and reducing their
efficiency. Sulfur dust gives easiest and quickest control.




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