Bulletin No. 32 New Series May, 1931 4
I THE PAPAYA|
iN A Fruit
+ Suitable for South Florida
JOHN M. SCOTT
State of Florida
+ Department of Agriculture
NATHAN MAYO, Commissioner
T J. APPLEYAR o, 1K...
FLORIDA EXPERIMENT STATTO"
A Fruit Suitable for South Florida
HE papaya (Carica papaya), sometimes called "pawpaw"
and "Tree Melon," is a fruit of great favor in most of the
tropical countries. Commercial plantings in this country
are limited chiefly to the southern part of Florida, although a
few plantings have been made in California and extreme south-
The plants are very susceptible to frost, and fruit of the best
type is produced only in those areas that are comparatively
frostless. Most of the commercial plantings in the State are
confined to Dade, Lee, Collier, Monroe, Broward, Palm Beach,
St. Lucie, Charlotte, Manatee and Sarasota counties. Occasion-
ally trees are grown farther north in the State, mainly as orna-
mentals, but they do not fruit very well under such conditions.
The papaya is a rapidly growing tree, often bearing fruit ten
months after planting. It is short lived and as a rule bears
fruit profitably for only three or four years.
Most growers seem to prefer hammock soils for papayas, but
satisfactory growth is made on a wide variety of soils. One
grower says his first choice is hammock, and his second choice
is good "pine" land. Good results have also been secured
when planted on good marl land. Muck, as a rule, is undesir-
able, because it makes a poor quality of fruit. The main thing
is to select a soil that retains moisture well so that the plants
never suffer from lack of water. At the same time, however,
it is necessary to see that the soil is well drained or the plants
will suffer from an over-supply of moisture.
The papaya is a gross feeder and it must receive plenty of
plant food for its best growth. Best results are obtained when
there is a liberal amount of humus and plant food available to
the plant. On the lighter soils it is, therefore, necessary to
fertilize rather heavily.
It is desirable to add cow manure or some other form of
humus under each young plant before it is set out. Then a
handful of commercial fertilizer is applied to each plant about
every two weeks until the plants bloom. The different growers
prefer different formulas for this fertilizer, some growers using
a 5-8-3 (5% ammonia, 8% available phosphoric acid, and 3%
DEPARTMENT OF AGRICULTURE
potash), while others prefer a higher percentage of potash.
Then when the plants begin to bloom, from two to four pounds
of a commercial fertilizer, analyzing around 5-8-10 is generally
applied every month or six weeks. It is preferable to have
most of the ammonia from organic sources.
Several growers recommend in applying the commercial fer-
tilizer that it be applied outside the leaf-line of the tree-that
is, applying it just far enough from the tree so that it will not
be under the leaves.
DISTANCE TO PLANT
Opinions of growers vary as to proper planting distance;
some plant 10 x 10 feet, others 8 x 8 feet. Still others make
their rows 9 feet apart and the plants 8 feet apart in the row,
It is largely a matter of personal choice.
Since the papaya is a rather short-lived tree, it is advisable
to plant about every three or four years. This can be accom-
plished by setting new plants between the old ones whenever
the older trees show signs of deterioration. For that reason it
is a good idea to raise a few new plants each year so as to have
new plants whenever needed.
Cultivation should be very shallow. A large number of the
feeding roots are found near the surface of the soil, hence the
necessity for shallow cultivation. One of the best methods of
cultivation is to keep the plants well mulched at all times. The
heavy mulching will keep down all weed growth, and at the
same time will conserve a large amount of soil moisture, which
is very desirable.
The papaya is propagated from seed. This means that all
plants are seedlings. Since the papaya may be cross-pollinated,
it means that the fruit does not reproduce true to seed. Seed
saved from a fruit of ideal size and shape will not necessarily
produce fruit of the same character.
One of the best ways to save seed is to screen in a plant that
bears fruit of the desired shape, size and quality, so that it will
not be cross-pollinated. Seed saved from fruit obtained in this
way will, in most cases, produce desirable fruit.
Plant seed about February 1. It is best to plant in flats or
pots. Then set the plants in the field about April 1 to 15.
Fig. 1-Young papaya plants growing in pots. They are now ready to transplant in field.
DEPARTMENT OF AGRICULTURE
Plants should be three or four inches high when transplanted.
Set from two to four plants in a hill. Thin to one plant in
hill as soon as false leaves appear.
Seed may be planted the year round, but best results seem
to be obtained when planted between February 1 and June 30.
It is always advisable to produce more plants than necessary
to plant a given area. Some few plants may die when trans-
planted; these must be replaced. Then, too, a large number of
the male plants should be replaced with female plants.
There is a wide difference of opinion among growers as to
the size the young plants should be when set out in orchard
formation. Some advise setting the plants when four to eight
inches tall. Other growers say do not transplant until one to
two feet tall or larger.
Whatever the size of the plants used when setting in orchard
formation, enough care should be given to the preparation of
the land so that it will be in the best condition to receive the
plants, in order that they may have a good chance to grow.
Dig holes for the plants in advance of the planting. If
possible, add a liberal quantity of barnyard manure or good
compost to each hill.
The plants when set in the hole, may be set the same depth,
or a little deeper, than they grew in the seed bed.
It is advisable to shade the plants for several days after re-
planting. Any cheap material may be used for this purpose.
All plants when transplanted should be watered frequently,
until they become well established in the new home. This is
particularly true of the papaya. Do not keep the soil water-
logged, but keep it moist so that the soil will not become dry
at any time during the first two weeks after transplanting.
If the plants are well mulched with straw, grass or litter of
any kind, this will not only retard evaporation, but will also
keep down weed growth and at the same time will keep the
soil in such condition as to induce a good growth of plants.
A BRAZILIAN METHOD*
My favorite way of getting papaya plants for setting out is
by sowing the seed in one-inch drills four inches apart and
four drills to the row. Then sow the seed in these drills, drop-
ping the seed about an inch apart.
Dr. P. H. Rolfs, Brazil, S. A., formerly Director Florida Agricultural
Fig. 2-An extensive planting of papayas. This photograph was taken at the end of the shipping season so that there
is but little fruit showing.
8 DEPARTMENT OF AGRICULTURE
When the young seedlings are about four inches high they
are thinned out to about four inches apart in the row.. This
weeding out gives me a chance to reject all seedlings whose
leaves show a reversion to the wild type, the deep lobing and
sharp pointed segments.
From time to time as the seedlings grow, those that show off
type in leaf and stem are rogued out. By the time the plants
are thirty inches tall there are only about four to the square
foot left. When these plants are about forty inches tall they
begin to show bloom buds in the axiles of the leaves. Then all
or nearly all, of the staminate plants are pulled out. The best
type of pistillate, and a sufficient number of the staminate ones,
are then set out in a permanent location.
I have less difficulty in losing plants by setting them out
after the first bloom buds show than when they are only a
few inches high.
In the tropics during the rainy season, trees three to six feet
tall may be pulled up by the roots and transplanted with only
a small percentage of loss.
When the seed is planted where the plants are expected to
grow permanently the plants are often spindly.
Another difficulty encountered by this method is that the
staminate (male), seedlings usually grow more rapidly than the
pistillate ones. If all the smaller ones are pulled out, there will
remain too large a proportion of staminate trees. This diffi-
culty can be overcome by letting all the seedlings grow until
they produce flower buds, then the staminate ones can be
rogued out until the right proportion for the orchard is at-
It is sometimes advisable to cut back the old plants when
they become too high. This will cause them to sprout out and
make a new top growth. When this is done, it should be
some time between the first of June and the first of August.
TYPES AND VARIETIES
As yet there are no distinct varieties that produce true to
seed grown in Florida. The two main types are the round
and oblong fruit. There does not seem to be any great differ-
ence in the quality of these two types, some people preferring
one type and some people the other. However, the long fruit
can be packed much more easily for shipment than the round
fruit, and is the type most generally shipped out of the State.
There is one point in the choice of fruits that should be given
careful consideration in the selection of fruits from which to
Fig 3-A nice planting of papayas in South Florida. Note how the rows are bedded up to Insure good drainage.
DEPARTMENT OF AGRICULTURE
save seed for planting. In addition to choosing fruit of the
most desirable shape, it is important to choose a fruit with
thick flesh. The papaya fruit fly causes much more damage
to thin-fleshed fruits than to fruit with a thick flesh.
Under ordinary conditions, the average yield of fruit -per
tree from commercial plantings is about 50 to lOpounds. Of
course, individual trees produce a great deaTinore than that,
but there are always a number of trees which produce very
little or no fruit, as well as the male trees which bear no fruit.
It is quite possible to increase the yield per tree by using
more care in selecting the fruit from which seed for planting
is to be obtained. There are records of a yield of 150 to 200
pounds per tree, but for a large commercial planting this is
much more than should be expected. The cultivation and fer-
tilization given will have its effect on yield. Neglected plant-
ings, that is, plantings without fertilizer or cultivation, will
produce very little or no fruit.
So far the demand for papayas has been very good. The
price ranges from five to twenty cents a pound, with an aver-
age of ten or twelve cents. At times the price may go higher
for the fancy grades. In shipping to distant markets it is
necessary that extreme caution be exercised in packing, as the
fruit is very easily bruised. Ice is also necessary, but the
temperature must not be allowed to go below freezing or the
fruit is ruined.
The fruit is packed in crates. Each fruit is wrapped in
paper. Various forms of advertising are used by the growers.
Some put their name and address on the crate. Others put
their name and address on each wrapper. One of the best of
these is shown in Fig 6 as used by H. W. Dorn & Company.
The number of fruit in a crate depends entirely on the size
of the fruit.
The market demand at the present time is for fruit that
weighs around four pounds each. Fruit of this size is much
more desirable to cut into half and serve than are fruits of
THE PAPAYA-A FRUIT
Y6 4 .o
Fig. 4-A male plant in bloom. Male plants produce no fruit.
DEPARTMENT OF AGRICULTURE
Fig. 5-A typical plant.
THE PAPAYA-A FRUIT 13
A TROPICAL TREE MELON
Favorite fruit of Americans in the tropics
Digested with Remarkable Ease
Never causes Indigestion
Particularly suited to stomachs
with weak digestive juices
HOW TO RIPEN
IF fruit is green when received keep in a cool room
at a temperature of 50 to 75 degrees depending on
how soon fruit is wanted to use. The papaya is ripe
and ready to eat just as soon as the pressure of your
thumb makes a dent in it. By this time it should show
distinct yellow coloration and should be placed in ice
chest. It is then ready to serve. After fruit is cut any
unused portion may be returned to the ice-box and
kept for days, as the cut surface seals over perfectly.
Do not keep below 50 degrees when green.
HOW TO SERVE
The commonest methods of serving are:
1. By cutting in halves, quarters or slices as one
serves cantaloupes. The seeds can easily be re-
moved with a spoon. It can be served plain or
with a light sprinkling of sugar with a little
lemon, orange or grapefruit juice.
2. Cut into cubes. Add a little sugar and a small
quantity of orange, grapefruit or lemon juice and
serve cold in fruit cups.
3. Cut into cubes or slices and serve as a salad
either alone or with other fruits, such as sliced
oranges or pineapple. Place on lettuce leaves with
addition of a little citrus fruit juice or mayon-
naise. Do not use French Dressing.
Fig. 6-Shows advertising used by some growers on the
wrappers used in packing fruit for shipment.
DEPARTMENT OF AGRICULTURE
Papayas may be used in numerous ways. If served for
breakfast or after dinner, they are cut lengthwise and eaten
with a spoon after the seeds and the thin gelatinous aril have
been removed. Salt, pepper, or lemon juice may be added
according to taste. The fruit is ripe when it gives way to the
pressure of the thumb.
The best way to prepare papayas is as follows: Ice the fruit
thoroughly. Cut the papaya into halves, remove the seeds and
the outer peeling. Then cut into cubes, mix with orange cubes
and sprinkle a little sugar on. An additional orange may be
squeezed on top of the cubes and served in a cocktail glass.
Sliced and served with whipped cream, papayas make a de-
licious dessert; and in combination with lettuce and sliced
cucumbers, a wholesome and nourishing salad. If eaten raw,
papayas somewhat resemble the northern cantaloupe.
Papaya marmalade and jelly are greatly relished, especially
if prepared with lime or lemon juice. Then there are numerous
other ways to utilize the ripe papaya-for pies, short-cakes,
sherbets and pickles. Unripe papayas can be boiled or stewed
and served as a vegetable, like squash or kohlrabi. The green
fruit also makes a delicious sauce resembling that made from
apples. Crystalized papaya cubes, if prepared carefully, make
some of the best candies that can be made from tropical fruits.
The papaya plant in its different organs-trunk, leaves, blos-
soms and fruit-contains a milky juice, the active principle of
which is called papain, a chemical closely related in its action
to animal pepsin, and used successfully as a remedy for a num-
ber of ailments, such as dyspepsia. Since the digestive proper-
ties of papain became better understood, it has attracted an
ever-increasing demand. Before the outbreak of the World
War, most of the papain used for medicinal purposes was im-
ported from India, and when the price went up to $25 per
pound complaints became numerous that it was adulterated.
The digestive properties of the papain are well recognized by
the natives of India, who wrap papaya leaves around a piece
of meat in order to make it tender.
The unripe fruit especially contains an abundance of papain
juice, which flows freely and is collected at the surface when
the skin of the fruit is lightly scored with a knife. The scor-
ing may be done several times before the fruit is picked and
does not seem to interfere with the eating qualities of the fruit,
Bulletin No. 4, New Series, Fla. State Department of Agriculture.
Fig. 7-A close up view showing how the papaya fruits sometimes. This gives a good idea as to the
size of the fruit.-Courtesy S. W. Hiatt.
16 DEPARTMENT OF AGRICULTURE
although the scores appearing on the surface as a result of the
bleeding make the fruit unsightly and therefore harder to sell.
The total sugar content of the ripe papaya differs according
to variety and season. Sometimes it exceeds 10 percent and it
is principally found in the form of invert sugar.
The papaya is a very common fruit in Hawaii and is served
in many different ways on the island. The following quotation,
taken from Bulletin No. 32 of the Hawaii Agricultural Experi-
ment Station, will give the reader an idea of the food value of
papaya, and some of the methods of preparing the fruit for
table use in Hawaii should be of interest to people in Florida.
The general composition of the papaya fruit is shown by the
W a ter ............................ ................ 90 .75
P rotein ....................................................................... .80
F a t ............................. ..... . ......... .1 0
F ib e r ......... .................................................. ...... .. ...... ..... ... ...... 1 .0 9
Nitrogen-free extract ................ .... ...... 6.32
A s h .................................................................................................. .... ...... 9 4
Reference has been made above to the nearly universal use of
the ripe papaya in the tropics as a breakfast fruit. For this pur-
pose it is cut lengthwise into portions and the seeds removed.
The placenta with the seeds attached may often be removed
without scraping the flesh, which is thus left in the most at-
tractive form for serving. Many prefer the choicest fruits
without other flavoring of any kind, but a little juice of the
lemon or the lime is a favorite accompaniment, while a few
prefer salt and pepper or even sugar. The green fruit when
fully grown may be cooked as summer squash, for which it
affords a very good substitute. The ripe fruit is used in mak-
ing papaya glac6.
The following recipes, taken from a book recently published,
give some directions for the use of this fruit :t
CHINA ORANGE AND PAPAYA MARMALADE, NO. 1
To 1 measure papaya allow 1/ measure China oranges. Wash
oranges well, squeeze out seeds and juice. Put skins through a meat
shopper and add the juice, strained free from seeds. Add papaya
pulp cut in small pieces and boil all together; then add as much sugar
as pulp. Boil again for 15 or 20 minutes.
Maine Sta. Bul. 158.
t Jessie C. Turner and Agnes B. Alexander, "How to Use Hawaiian
Fruits." Honolulu. P. 17, 42, 43.
THE PAPAYA-A FRUIT 17
CHINA ORANGE AND PAPAYA MARMALADE, NO. 2
To 6 cups papaya cut in small pieces add 1/3 cup China orange
juice. Boil 15 minutes and add half as much sugar as pulp. Boil
again for 15 or 20 minutes.
STEWED PAPAYA, NO. 1
2 cups diced papaya Juice 2 lemons
% cup sugar 1% cup water
Cut papaya in dice and stew with sugar, water and lemon juice
% hour. Serve in sherbet glasses as a first course for luncheon, or
a dessert. Can use 4 China oranges in place of lemons.
STEWED PAPAYA, NO. 2
Cook in the same manner as No. 1, with 1/4 cup sugar and only
enough water to keep from burning. Serve as a vegetable.
Cut papaya in halves lengthwise. Add a little sugar and China
orange, lime, or lemon juice; or a little cinnamon in place of the
juice. Bake 20 minutes and serve immediately on taking from the
oven. This is a vegetable.
Make sirup of 1 measure sugar and measure vinegar. Add a few
whole cloves and peppercorns and 2 measures of half-ripe papaya, cut
into small pieces. Boil until tender.
PAPAYA AND GINGER
Make a sirup of 1 measure of ginger, % measure water, some finely
sliced dried ginger, and a few slices of lemon. Add 2 measures half-
ripe papaya sliced lengthwise, which has been previously simmered
in water until clear, but not broken.
Cut papaya in dice and serve in glasses with cocktail sauce and
chipped ice. Or serve with China orange, lemon or lime juice, and
little sugar in same manner.
PAPAYA SALAD, NO. 1
On a strip of peeled papaya lay small bits of pomelo and orange.
Serve with mayonnaise on separate plates, and garnish each with one
or two nasturtiums and leaves.
PAPAYA SALAD, No. 2
Cut papaya in cubes and add 8 small Chinese onions and 5 pieces
green celery chopped fine. Serve with boiled dressing.
To 1/. cups papaya pulp add juice 1 lemon, % cup sugar, and beat
into 2 stiffly whipped whites of eggs.
1 box gelatine 1 cup boiling water
cup cold water 1 cup papaya pulp
Juice 1 lemon 1 cup sugar -
Soak gelatine in the cold water 5 minutes. Dissolve the sugar in
the boiling water, add gelatine and strain. When cool, add the papaya
and lemon juice. Place on ice to harden.
18 DEPARTMENT OF AGRICULTURE
.. t> ij '.
f. - _. .. ' ^ .. .-^;,
Fig .8 Ds u .C S. U. t u-
Fig. 8-Desirable size and type of fruit.-Courtesy S. U. Stambough.
THE PAPAYA-A FRUIT 19
2 eggs Juice 1% lemon
1 cup papaya pulp 1 cup sugar
% cup butter
Make a bottom pie crust and bake. Cream butter and sugar. Add
beaten eggs, lemon juice and papaya. Pour into pie crust and bake.
Make a meringue of white of eggs and 2 tablespoonsful of sugar. Place
on pie and brown in oven.
Mix 4 cups papaya pulp with 2 cups sugar and juice of 2 lemons,
In the interior of the papaya stem is what some people call
the heart. This is the soft interior inside of the woody layer.
When a large tree is sacrificed this inner heart, especially near
the foot of the stem, may be taken out and grated like cocoa-
nut. It has a pleasing flavor and is delicious. It may be pre-
pared in the various ways that cocoanut is used. Its flavor is
different from it but by the unsuspecting might easily be mis-
taken for cocoanut. A servant in the interior of Brazil pre-
pared several dishes for us, and, so far as I know, this is the
first time reference to this appears in print.
P. H. Rolfs.
PAPAYA AS HEALTH FOOD
The well known health authority, Dr. John Harvey Kellogg,
head of the Battle Creek Sanitarium in Michigan, in a recent
address had the following to say regarding papayas as a health
"I became acquainted with the papaya in Cuba forty years
ago, and have had a hankering for it ever since. It is certainly
one of the choicest of the many marvelous -fruits, which the
tropics produce. Every time I have come to Florida I have
looked for papayas. I happened two or three times to be able
to get a taste of the fruit in Miami, but usually failed to find
it. Last spring when I was here I heard that you had planted
out three or four hundred acres which would be coming into
bearing last fall. I thought you certainly would be swamped
with a tremendous crop for which you would not be able to
find a market so I came down this winter to help you eat it up.
I am delighted to see that the demand is fully equal to the
supply. I hope this new industry will grow to such propor-
tions that the rest of the country may be able to share this
excellent fruit with you. I am feasting on papayas every day,
and quite agree with one of my secretaries who remarked the
other day, 'these papayas grow better every day.' It is a
20 DEPARTMENT OF AGRICULTURE
Fig. 9-The size of the fruit can be judged by comparing with the water bucket
THE PAPAYA-A FRUIT
glorified melon which has climbed into a tree to display its
superior qualities. Its delicate tropical fragrance and delicious
satisfying flavor are qualities of which one does not tire.
"Studies in nutrition laboratories have in recent years shown
us more clearly than was understood before the enormous im-,
portance of fruit as a dietary staple. There is a natural craving
for fruit, which indicates recognition of its value. Fruits are
the best source for certain elements of foods which control the
nutritive processes of the body and aid in the utilization of
other food stuffs. These substances, known as vitamins, are
the most remarkable of all food or chemical substances which
have ever been discovered. As a matter of fact they are not
yet discovered, for no one has ever seen a vitamin. They are
highly potent in quantities so small that they cannot be meas-
ured by the most delicate chemical methods, and yet they are
so important that whenever one of them is absent from an
animal's food it quickly languishes and ultimately dies.
For convenience, vitamins are named after the letters of the
alphabet and are known as A, B, C, D, etc. Vitamin A makes
young animals grow and enables the body to resist the attacks
of germs. When it is absent children and small animals get
sore eyes and stop growing. When Vitamin B is absent, growth
is arrested and paralysis develops. A few years ago 15,000
people died in the Philippine Islands every year from beriberi
due to this cause. The absence of Vitamin C produces scurvy.
A deficiency of Vitamin C is one of the causes of imperfect and
decayed teeth. Bottle-fed babies often die of scurvy because
Vitamin C is lacking. Florida oranges are saving the lives of
thousands of babies all over the country because they are rich
in Vitamin C. Vitamin D prevents rickets and helps the body
to utilize lime in building the bbnes. When it is absent the
bones are flexible and permanent deformities develop. * *
"I have been especially interested in investigating the vita-
min content of the papaya. Work done in Honolulu and the
Dutch East Indies indicates that the papaya is rich in Vitamin
C, which makes the orange so valuable, and is very rich in Vita-
min A. This vitamin is associated with the yellow color of
foods and is found not only in butter, but in yellow corn and
carrots. The yellow color of the papaya leads me to suspect
that it contains Vitamin A, and on investigation I find that
studies which have been made in Honolulu and the Dutch East
Indies show the papaya to be very rich in Vitamin A. This is
highly important for Vitamin A is rare in fruits. The D vita-
min, which prevents rickets, is usually associated with Vitamin
DEPARTMENT OF AGRICULTURE
Fig. 10-Fruit on this plant when ripe weighed from 4 to 4/2 pounds each. A
very desirable size.
THE PAPAYA-A FRUIT
A, but these vitamins are often deficient, and in countries
where there is a lack of sunshine, rickets is, on this account,
very common. * *
"No research has as yet been made to determine certainly
whether this Vitamin D is present in the papaya but the fact
that it is very rich in Vitamin A is good reason for believing
that Vitamin D is there also, for these two vitamins are prac-
tically always found together. To make the matter certain, I
am having a special investigation made to *ottl- the question
definitely. If our research shall prove, as I believe it will, that
Vitamin D is present in the papaya, this fact alone should
create an enormous demand for this fruit. I am certain that
every one of the several hundred thousand babies that are now
teing fed cod liver oil would be very glad to be given papaya
marmalade instead. * *
"I am investigating two other points of much interest in rela-
tion to the papaya. Most fruits are of great value in the diet
because they combat acidosis. There is a natural tendency to
the accumulation of acids in the tissues. An excess of acids
causes fatigue, loss of appetite, headache and premature old
age. A research made in the laboratory of the Battle Creek
Sanitarium some years ago by Dr. Blatherwick of Yale Uni-
versity, showed that all fruits are rich in alkalies, which neu-
tralize the poisonous acids of the body and so help to maintain
the necessary alkali reserve of the blood. This is a fact of
great importance because so many of our foods, especially
meats, eggs and even breakfast foods, contain an excess of
acids. A bread and meat diet, as McCollum has pointed out,
is, on this account, about the worst diet a person can take.
Vegetables and fruits are the natural antidotes for disease-pro-
ducing acids. Blatherwick showed the cantaloupe to be richer
in these useful organic alkalies than any other food. The
analysis thus far made of the papaya show it to be a strong
rival of the cantaloupe, and possibly it will prove to be su-
perior. * *
"The study of the papaya from a health standpoint has only
just begun, but the facts already known indicate that the
papaya possesses qualities which make it capable of rendering
a priceless service to the people of the United States. *
"I am sure that when the people of the North become thor-
oughly acquainted with this delicious fruit and are educated
to appreciate its precious value from a dietetic standpoint,
southern Florida will find a ready market for all the papayas
it is able to produce."
24 DEPARTMENT OF AGRICULTURE
Fig. 11-Papaya plant showing a very desirable type and size of fruit.
THE PAPAYA-A FRUIT
MEDICINAL AND OTHER USES
Papaya bark is used in the manufacture of ropes. Nearly
all parts of the plant are credited with some medicinal value.
The roots afford a nerve tonic. The seeds are said to be anthel-
mintic, emmenagogic, and carminative. They are also eaten
as a delicacy and as a quencher of thirst. The ripe fruit finds
a place as an ingredient in certain sirups and elixirs, which are
said to be expectorant, sedative and tonic.
The most important medicinal property of the plant is found
in the milky juice. This is used by the natives of the tropics in
the treatment of eczema, warts, intestinal worms, ulcers, and
many kinds of foul sores, in diphtheria to dissolve the false
membranes in the throat, and for numerous other ailments.
The ripe fruit is used as a cosmetic, a slice of it being rubbed
upon the skin to remove freckles and other blemishes. The
green fruit and the leaves are employed as soap to remove
stains from clothing.
No single use of the papaya, except for food, is so common
in the tropics as that of the milky juice in rendering tough
meat tender. For this purpose a slice of the green fruit, rich
in juice, is rubbed over the tough flesh, or the latter is dipped
for a few minutes in a solution of the juice. Sometimes a piece
of the green fruit is put in the water in which the meat is
Another practice is to wrap the meat in papaya leaves over
night, or even to hang it in the papaya tree. The feeding of
green papayas to hogs is reported to make the pork tender.
Some of these practices are of doubtful efficacy. Some writers
recommend mixing ginger with juice when it is to be applied
It is doubtful if Florida will ever be able to compete with
foreign markets in manufacturing papain, yet it may be worth
while trying. To such growers as would be interested in rais-
ing papayas for papain extraction, the following remarks by
V. A. Beckly, printed in the Journal of the Department of Agri-
culture, Union of South Africa, may be helpful:
"It is well known that the juice of the papayas will render
tough meat more tender. This is due to a ferment (papain)
which possesses the power of digesting protein materials such
as meat, egg white, the curd of milk, etc. Its action is similar
to the two well-known body ferments, pepsin and trypsin. On
account of its efficiency being greater than that of pepsin, it
is largely replacing that substance as a diug.
DEPARTMENT OF AGRICULTURE
"Papain appears on the market in the form of a white or
creamy powder, easily pulverized between the fingers. It has
a characteristic pungent smell. It should not be discolored,
nor should it possess any malodor. The presence of any dark-
ening generally indicates improper manufacture, while a bad
odor shows that a certain amount of decomposition has taken
place. If placed on the market in such a condition it would
command a very low price, if, in fact, there were any demand
for it at all.
"Papain is often adulterated with starch and similar sub-
stances. Such adulteration detracts greatly from the value of
the article, but is more easily detected. Further, papain is
generally bought according to assay, its power of digesting
casein being the criterion of value. Not only does this assay de-
termine the digesitve power of the sample, but it also provides
a means of detecting adulteration with other protein-splitting
"Papain is very easily obtained in its commercial form by
simply drying the latex or milk that exudes from the rind of
a green papaya fruit. As long as certain simple precautions
are observed, it is within the power of any grower of papayas
to produce papain of a higher merchantable value.
"The latex containing the papain is best obtained from full-
grown or nearly full-grown, well-developed green papayas by
scratching or making shallow cuts in the rind with an ivory,
bone or wooden knife. Very young fruits give a latex that is
rather weak in digestive power, while the ripe fruit gives very
very little, if any, milky juice.
"The juice that exudes is collected in a glass or china vessel,
which must be scrupulously clean. After a short while the
milk coagulates in the cut and the flow ceases. The curd is
carefully removed from the cut and added to the milk in the
vessel. The fruit may be tapped several times at an interval
of a few days until it begins to show signs of ripening.
"On no account should a steel knife be used in cutting fruit,
nor should the latex be collected in a tin. Either of these will
cause the resulting papain to be blackened or darkened, and
thus decrease its market value. Sometimes a ,dark-colored
latex is obtained from the fruit even though no iron utensil
has been used. Such latex should be discarded.
"Shortly after collection, the whole mass of the latex coagu-
lates, forming a pure white curd. This must be rapidly dried
lest decomposition should set in, spoiling the material. On a
small scale the drying may be carried out by spreading the
curd thinly on sheets of glass and drying in the sun. If the
drying be commenced not later than about midday, the curd
THE PAPAYA-A FRUIT
should, by nightfall, be sufficiently dry to insure that no de-
composition will take place during the night. The next day
the curd can be completely dried.
"Sun-drying is most uncertain and very nearly impracticable
on a large scale. Artificial drying by means of a fruit evapora-
tor or a drying stove is more satisfactory and yields a better,
more uniform, product. The curd is spread on brown or un-
bleached linen stretched over light wooden frames that fit the
dryer to insure rapid drying.
"An easily constructed drying stove is the type used in the
West Indies. This consists of a brick chamber 3 feet high, 3
feet wide, and 6 feet long, open at the top; the dimensions may
be changed to meet the requirements of the grower. About a
foot from the top a sheet of iron is fixed horizontally across
the chamber. A small firebox is constructed at one end and a
chimney at the other end.
"In using the dryer, a layer of sand is placed on the sheet of
iron to keep the temperature as even as possible. A frame is
placed over the top of the chamber, forming, as it were, a lid
or cover, when the hot air drives off the moisture. Great care
must be observed to maintain as low a temperature as possible.
At no time should the temperature of the tray exceed 100 de-
grees F., as above this point the activity of the product is
"As the material dries it shrinks greatly, so that eventually
the partially dried contents of several trays may be placed in
one tray and the drying completed. The drying is continued
until the material shows no stickiness and is crisp throughout.
While still warm it is ground finely in a mill (a coffee mill is
very suitable) and the powder packed in clean air-tight tins,
or preferably bottles."
HOW TO EXTRACT THE LATEX*
The latex is secured by making a scratch or shallow incision
in the skin of the fruit while still green. Steel knives are some-
times used, but they are not recommended. Bone, glass or a
sharp-edged piece of bamboo is more usually employed. The
milky latex exudes and should be caught in containers, which
may be made out of the leaf sheaths of areca palms. Fruits
may be tapped every 4-5 days or at longer intervals until they
cease to yield, and a plantation is reported to be profitable until
the end of its third year if the soil is good and general condi-
tions favorable. Tapping must be done in the early morning,
and in every case should be completed before 10 A. M.
Leaflet No. 44, Department of Agriculture, Ceylon.
DEPARTMENT OF AGRICULTURE
The latex soon becomes coagulated and forms a white curd
possessing a somewhat pungent smell. Drying must be effected
as speedily as possible, otherwise decomposition sets in. When
considerable quantities of latex are being collected this work
should be undertaken early in the morning so that drying may
begin before midday. This insures that by evening the material
is sufficiently dry to keep without deterioration until the fol-
lowing morning, when the drying can be completed.
Drying can be hastened if the coagulated curd is passed
through a collander so as to come out in the form of small
worms. When small quantities or being prepared, a potato
squeezer has been used with great advantage.
DRYING OF LATEX
Drying of latex must be effected without delay but should
not be too rapid. In dry weather, drying in the open may be
adopted. Drying in the sun is not to be recommended as the
product becomes darkened. Some form of drying apparatus
is necessary when large quantities of latex have to be dealt
with, and is generally to be advised in Ceylon on the south-west
side of the island where weather conditions are rather un-
The following is a summary of experiments which were
carried out at the Experiment Station, Peradeniya:
Method of Tapping I per Tree,
Long papaya trees
tapped every 8th day 12 34 1,460 722.95 2.08 in 34 tappings
Round papaya trees I
tapped every 8th day 12 34 1,126 726.0 2.08 in 34 tappings
Long papaya trees
tapped every 5th day 12 52 1,682 789.9 2.25 in 52 tapping
Long papaya trees
tapped once a week 12 35 1,003 495.5 1.41 in 35 tappings
Papaya trees tapped
every 10th day .......... 204 17 7,781 5,689.15 1 3.88 in 17 tappings
It is generally estimated that a good yield is 175 pounds per
acre, but growers have informed the Department of Agricul-
ture that average yields of 100 pounds per acre per annum for
first year after coming into bearing would be satisfactory
for flat lands and 80 pounds per acre per annum for hilly or
rocky lands. In the second year the yield is roughly one-half
of that of the first year.
THE PAPAYA-A FRUIT 29
BIOLOGY OF THE PAPAYA FRUIT FLY IN FLORIDA*
( T"., t. 1 i Curvicauda)
The occurrence in 1905 of a newly introduced species of fruit
fly (Toxotrypana curvicauda Gerst.) attacking the papaya
(Carica papaya L.) in South Florida was the occasion several
years later for a preliminary investigation and paper on the
insect by Knab and Yothers. Technical descriptions of the in-
sect, together with its distribution and history, are recorded
therein, and also some notes on its habits. In recent years the
pest has assumed much greater economic importance, due to
the increasing production of the papaya from a commercial
standpoint, and also to the spread of the insect over nearly all
portions of the State where papayas are grown. Hence a care-
ful study of its biology and control was undertaken by the'
It is the purpose of this bulletin to present an accurate ac-
count of the life history and seasonal history of the insect, to-
gether with its habits and the factors influencing its develop-
ment and spread. The methods of control as far as worked
out are also given.
DESCRIPTION AND LIFE HISTORY
The eggs (Fig. 12) are of very unusual proportions, being
long and slender, somewhat club-shaped or fusiform, with a
long cylindrical stalk. The average length is about 2.5 mm.
and the greatest diameter is 0.2 mm. They are inserted into
the seed cavity of the fruit from the long ovipositor of the
female. The stalk sometimes remains partly in the flesh, al-
though the eggs are never placed there as the young maggots
seem unable to survive there. They always occur in clusters,
and usually there is only one cluster to a fruit. The cluster
consists of from 6 to 20 or more eggs, which are always fastened
together by an adhesive substance on the surface of the eggs.
One female, according to Knab and Yothers, is capable of lay-
ing 103 eggs, all of which are disposed of at about the same
The eggs require from 12 to 14 days to hatch at any time
throughout the year. Although the other stages are longer
in winter than summer, the eggs seem not to be affected by
climatic changes. This point was determined by cutting open
Department of Agriculture Bulletin No. 1081.
DEPARTMENT OF AGRICULTURE
infested fruits at definite intervals after they were stung.
Usually an adult would oviposit in several fruits on a tree the
same evening. It was then possible to cut one of these on each
of several successive days until the eggs were found to have
hatched. Even in the fruits which had been cut the eggs would
complete their development if the halves were placed together,
provided they were several days old when first exposed to the
light and air. With freshly laid eggs this was not found to be
true. Many attempts were made to rear the eggs artificially
after removing them from the fruit but without success. When
dissected from the fruit and placed on a piece of leaf or fruit
pulp over a plug of wet cotton in a vial inverted in water, as
practiced by Back and Pemberton with melon-fly eggs in
Hawaii, they failed to develop. Even though the conditions of
heat and moisture were apparently the same as in the fruit they
did not hatch.
When ready to hatch the eggs split longitudinally along the
micropylar half and the maggot escapes, leaving the stalk end
The young maggots on hatching from the eggs begin at once
to feed on the coating of the seeds. They remain for about the
first half of their existence within the seed cavity, feeding on
the seed coverings and other fibres there. Many of the seeds
become detached by this process, and the loose seeds in the
fruit serve as an indication of their presence. When newly
born the maggots are almost transparent, but soon assume a
shining, dirty white color while in the seed cavity. Later on,
as they continue to develop, they eat into the flesh of the fruit,
first close to the cavity, and then working farther out until,
when mature, they are close to the skin. They have then only
to eat a hole through the rind to escape. During this latter
part of their life they become a rich golden yellow color, like
the color of the fruit on which they are feeding. The presence
of the maggots in the fruit usually causes it to turn yellow and
ripen prematurely. This is a distinct advantage to the larvae,
for they do not like the juice of the green fruits and usually
remain around the seed cavity until the flesh begins to soften.
The mature maggots (Fig. 12) average about 11 mm. in
length, are subeylindrical in shape and taper anteriorly to the
The length of time required for their development varied
from 10 to 27 days in a large number of tests. The cooler
weather of winter prolongs somewhat the length of the larval
stage. Conditions unfavorable to the larvae, such as the fruit
decaying or the maggots being removed from the fruits, will
THE PAPAYA-A FRUIT 31
cause them to transform before the normal time. On the other
hand, if the conditions are favorable the larvae may remain in
the fruit for several days after reaching maturity. The aver-
age time for this stage is 15 days.
They make their escape by eating a hole through the skin
and dropping to the ground. As a rule, when one escapes the
others will follow in rapid succession, and often all emerge
from the same exit hole. If the fruit has already fallen from
the tree the maggots go into the ground immediately under it;
if the fruit is still on the tree they drop to the ground. Often
a larva will remain partly emerged from a fruit and continue
a wriggling, twisting motion for an hour or more before finally
droppirg. When once on the ground, the maggots immediately
bury themselves and never wander around on the soil. The
x2; b, eggs, x20.
Fig. 12-Toxotrypana curvicauda. A, Adult flies: a,female; b, male, x2. B, Puparia, x1/s2 C, a, Larvae,
x2; b, eggs, x20.
THE PAPAYA-A FRUIT
transformation is completed within a few hours after entering
the ground. The period of exposure from the time of leaving
the fruit to entering the soil ordinarily would be only a minute
or two, and consequently there would be little chance for para-
sitism here. Very rarely a maggot will pupate inside a fruit.
The number of maggots in a single infested fruit sometimes
runs up as high as 40, although ordinarily there are about 15
or 20. A very small fruit may have only 2 or 3.
If confined in breeding jars where no soil is present the
larvae usually will not pupate. In a glass stender dish or
Petri dish the mature maggots would remain in the larval
stage for three or four days, continually crawling around the
dish. After several days they attempt to pupate, but many
of them die before completing the transformation. Even when
they succeeded in pupating, the adults never matured from
them. Evidently this is due to a lack of moisture, which seems
to be a vital factor to all stages of development in this insect.
In common with other fruit flies, this insect passes the pupal
stage in the ground. The puparia occur naturally under the
infested trees in the soil, for, as stated above, the maggots do
not travel around, but go into the ground where they fall. The
average depth of the puparia is two inches, although they vary
anywhere from the surface to 3 inches deep, and sometimes
occur also under rock and rubbish on the surface. The moisture
in the earth seems to determine largely this point, for they go
down until they can get into damp soil. Very rarely one is
found inside the fruit either on the tree or on the ground.
The puparia (Fig. 12) are of a stout, subcylindrical form
with rounded ends and vary in length from 8.5 to 12 mm. The
size is no indication of sex, for from 100 of the smallest ones
obtainable about an equal number of males and females
emerged. The color of the puparia varies all the way from a
light ferruginous yellow to dark brown or almost black. This
color in no way indicates their age, for some remain light col-
ored throughout their existence.
The pupal stage was found to vary from 18 to 44 days in
breeding out several hundred in all months of the year. Aside
from the temperature changes the effect of the moisture is a
very large factor in this regard. Under favorable conditions
of moisture the largest number of the adults will emerge after
18 to 20 days in hot weather, but in winter this runs up between
30 and 40 days on the average. Hooker found it to last from
DEPARTMENT OF AGRICULTURE
17 to 21 days in Porto Rico. Moisture, even more than heat,
seems to be the determining factor. Lack of moisure will pro-
long very materially the pupal stage and if continued will
prove fatal. On the other hand, excessive moisture will kill
the puparia. The following data prove this point:
One hundred fresh puparia placed in soil in a jar and kept
without any water being added. All died.
One hundred fresh puparia placed in soil in a jar and kept
moderately moist; 80 adults emerged. Twenty. died.
One hundred fresh puparia placed in soil in a jar and kept
wet every day. All died.
Even under the most favorable conditions of heat and mois-
ture the puparia do not all mature, and 70 per cent is a very
good average. Under natural conditions the average runs be-
low that. Several hundred puparia placed in jars, some of
them reared from larvae and others gathered in the soil under
trees, gave results as shown in Table I.
TABLE 1.-Males and Females of Toxotrypana Curvicauda Maturing
From Puparia Placed in Jars.
Number Number Number Total Total
of Pupae of Males of Females Emerged Died
870 279 281 560 310
Thus it is seen that only 64.3 per cent matured into adults,
while 35.7 per cent died. Of the number maturing, practically
50 per cent were males and 50 per cent females.
Practically all the adults emerge from the soil in early morn-
ing just before daylight. Very rarely will one emerge between
sunrise and midnight. The adults often carry the pupal case
to the surface of the ground before freeing themselves of it.
Only a few minutes are then required for their complete de-
The adult of this species (Fig. 12) is a wasplike fly, very
much resembling in coloration and general appearance the
Mwasps of the genus Polistes. The body is yellow and brown
marked with black, and the females are made strikingly con-
spicuous by a long, curved ovipositor, even longer than the
body itself. There is considerable variation in the size of the
flies, but they average about 12 mm. in length. The ovipositor
of the female varies from 10 to 14 mm. in length.
The flies exhibit a rather rapid flight and walk with a quick,
nervous motion. The females are not often seen on bright
days, but appear about the trees to lay their eggs in the late
THE PAPAYA-A FRUIT
afternoon or evenings. They show a negative reaction to sun-
light and always seek the shady side of the tree or fruit. Al-
though sometimes seen during the morning and noon hours,
the greatest flight occurs about an hour before sunset. The
males, however, are more active on bright days. Both sexes
are easily disturbed when resting on the fruits.
The life of the adult flies is probably only a few days in
length. They have been kept alive in captivity for 31 days
when properly fed, although the average is very much less.
The flies will eat any kind of sugar syrup and the pulp and
juices of some fruits, but they never appear to be attracted
by any kind of food. Many will die without ever eating when
food is placed at their disposal. Others will eat only when
food is placed directly in front of them or when they happen
to walk into it. When they have once tasted the sweets they
will feed until the body is well distended. The best results
were obtained by placing drops of brown-sugar syrup on the
net or screen covering of the cages. In the large cages it was
sprayed with an atomizer on the under side of the leaves of
the tree. The flies have a liking for the pulp of ripe papayas
and also eat bananas, but will not eat the juice of oranges.
The following figures show the length of life of some of the
Fifty-four flies confined without food after emerging lived
from 1.5 to 5.5 days, with an average of 3.45 days.
Thirty-six flies given water only lived from 3 to 6 days with
and average of 4.6 days.
Seventy-six flies fed on sugar sirup lived from 3 to 31 days
with an average of 7.4 days.
Under natural conditions these figures probably do not vary
much. Five to seven days represent an average life for the
The insects copulate usually on the leaves or fruits of the
papayas, but can only rarely be observed. Copulation takes
place during the daytime, for the male is more active then, as
noted above. He seems to experience some difficulty in holding
the female in position because of the long ovipositor. To ac-
complish his object, he alights on top of the female and, clasp-
ing her body with the first two pairs of legs, he draws the
ovipositor back and up with the remaining pair. Then by
practically standing on his head he is able to bring the tip of
his abdomen in conjunction with the end of the ovipositor.
They usually hold this position for several minutes or longer,
36 DEPARTMENT OF AGRICULTURE
one pair being observed to remain for nearly two hours. If
disturbed the female will walk around the fruit or even fly to
another tree, always carrying the male along in position. In
captivity the flies very seldom copulate. This is true when con-
fined in the large cages over the trees as well as in small cages
or jars in the laboratory. Of several hundred adults bred out
in jars and observed at all hours of day and night, only a few
ever made any attempt at copulation. These cases happened
when the flies were 4 or 5 days old and had been fed on sugar
sirup or fruit pulp. If given no food they soon die without
Oviposition usually takes place in the evening, that being the
time the adult females are most active. It has been observed
occasionally, however, to take place at all other times of the
day. The fruits selected by the females in which to lay their
eggs are usually medium or larger sized, if all sizes are present
on the plant. They often begin work on a plant when the
fruits have just set and are very small, and all sizes of fruits
are subject to attack. They seem, however, to prefer the half-
grown or larger fruits, perhaps due to a natural instinct, foi
if the eggs are deposited in a nearly mature fruit, the fruit
may ripen and decay before the maggots have completed theii
growth. On the other hand, if placed in very small fruits the
maggots will mature before the fruit has started to ripen, and
they sometimes experience difficulty in escaping from green
fruits. It has been said that the milky juice from the green
fruits is fatal to the larvae, but this has not been found to be
true. In fact, maggots which have been rolled around in the
juice from green fruits completed their development.
It is not often that an adult fly will oviposit in a fruit where
eggs or maggots are already present, although in a few in-
stances maggots of two distinct sizes were found. When the
first ones to mature escape they cause the fruit to decay, so the
younger ones may not be able to complete their development,
The adult fly alights on the fruit selected and usually walks
around for a time with a nervous motion. When she has found
a suitable place she forces her ovipositor through the skin and
flesh of the fruit and deposits her eggs inside the seed cavity.
This is accomplished by raising the long ovipositor up in a
curved position and placing the tip of it on the fruit near the
end of the abdomen, then forcing it through the fruit. The
position taken is much the same as that of the ichneumon flies
in depositing their eggs.
THE PAPAYA-A FRUIT 37
The eggs are laid in clusters and ordinarily only one cluster
will be placed in a single fruit, although occasionally two or
three are found. The fly often stings a fruit several times, as
many as 10 punctures being counted at times, but does not
always deposit a cluster of eggs. Possibly she is not able to
reach through the flesh of the fruit in all places and hence
withdraws and seeks a new place. In fact, many fruits are
stung several times and no eggs laid in them. This has often
happened in the breeding cages where fruits supposedly con-
taining eggs failed to develop any maggots. Also many fruits
on the trees have been marked after being stung and no larvae
ever appeared in them. Usually about two minutes are re-
quired by the females to deposit the eggs, although instances
have been noted where the ovipositor remained inserted for an
hour or more. Occasionally a female will become trapped and
die in the milky juice which wells up when the skin is punc-
tured. This exudate coagulates and holds the fly if she does not
escape soon. Whenever a fruit is stung the exudate produces
a characteristic mark by running down the side of the fruit and
also coagulating in a large drop at the puncture. It is possible
thereby to determine easily the number and location of the
SEASONAL HISTORY AND OCCURRENCE
The insects breed throughout the year in Florida and are
present in all stages in any month of the year. They have,
however, some seasonal preferences and occur in much larger
numbers at some seasons than others. The time of greatest
flight of the adults seems to be in March and April, while in
the late summer and fall there are very few of them in evidence.
This is correlated largely with the growth of the host plants,
which begin fruiting usually in the fall and continue through
the winter and spring. Many of the plants die down or are
cut out in the late spring and new ones set. The flies, therefore,
appear on the new fruits in the fall and continue to breed in
increasing numbers throughout the winter and spring. The
wild papayas in the hammocks fruit at all seasons and always
serve as host plants whether or not any cultivated sorts are
available. The generations are by no means marked and vary
in length from 40 days in summer to 70 or more in colder
weather. In a year's time there are about six generations, al-
though they overlap and are in no way distinct. Moisture in
the soil is a very important regulating factor in the length of
all stages, perhaps even more so than changes of temperature.
DEPARTMENT OF AGRICULTURE
POWER OF FLIGIIT
The distance which the adults are able to travel is not great,
for they are not strong fliers. One planting of papayas under
observation was placed two miles from where any other plants
existed and remained free from infestation throughout the sea-
son, the adults apparently being unable to cover that distance.
In most locations, however, there are wild papayas all through
the surrounding hammocks, and these serve to harbor and
SUSCEPTIBILITY OF VARIETIES
While no distinct variety of the papaya (Carica papaya) is
recognized, there are several types of the fruit grown in the
State. -Several have been introduced from foreign countries
and crossed on existing types. Then there are the original
wild types which have been cross-pollinated on the cultivated
plants through natural agencies. Through all this cross-pollina-
tion there result two rather distinct types of fruits, one the
small, round or oval type with rather thin skin and flesh, and
the other the large oblong fruits which usually have thick flesh.
One specially fine fruit of the latter type has been produced
at the Plant Introduction Gardens at Miami, Florida, by Mr.
Edward Simmons and is known as No. 28533. These oblong
fruits are much more immune to the attacks of the flies, due
largely to the fact that the female flies are unable to reach
through the flesh of the fruit with their ovipositors and lay
their eggs. In fact in some places they were found practically
free from infestation and are considered immune by the grow-
ers. An examination of about 300 fruits of all kinds on the
Florida Keys by A. L. Swanson, an inspector of the State Plant
Board of Florida, showed 90 per cent of infestation in the small
round fruits, as compared to no infestation in the large oblong
fruits. This latter fact has not held good, however, by the
writer. Several hundred fruits examined both on the Keys and
in many places on the mainland showed about 88 per cent of
the round or oval fruits infested and about 15 per cent of the
oblong fruits infested. In wild fruits in the hammocks the
infestation is close to 100 per cent. No papayas grown in the
State are entirely immune from the flies.
THE PAPAYA-A FRUIT 39
Only two natural enemies have been noted on this insect,
one the jumping spiders, and the other the small red ants which
sometimes prey upon the larvae. The large black jumping
spiders conceal themselves between the fruits on the trees and
are then able to catch the flies when they alight near them.
Doubtless they destroy many in this way. On a few occasions
ants have been observed attacking the maggots in a fruit which
had fallen to the ground. They enter through the exit hole
of the first maggot to escape and can then destroy the remain-
ing larvae in the fruit. They represent a negligible factor,
however, in the control of the pest.
Six hundred pupae dug from the soil under the trees and
bred out in jars failed to produce a single parasite. The insect
is well protected from the attack of parasites through nearly
the entire period of its life.
The most effective way of preventing injury from this pest
is by I, ,i-i the fruit or trees. Either cheesecloth or mosquito
netting can be tied over the trees, or around the individual
fruits, and the flies will not try to sting the fruits through it.
However, this plan is hardly practicable on a large scale, since
it requires considerable work and expense and, in many cases,
changing the bags as the fruits grow larger. The adults are
readily killed by feeding them a poisoned sirup, the best results
being obtained by using sodium arsenite or potassium arsenate
dissolved in brown sugar sirup. When given this sirup the
adult flies die very soon after feeding, and they eat it as readily
as the plain sirup. Very good killing results were also ob-
tained by spraying this mixture with an atomizer on the under
side of the leaves of the trees in the large cages. Large num-
bers of flies were found dead on the ground within a couple
of hours. These soluble poisons, however, burn the trees very
severely and cannot safely be used. Even at the rate of 1 lb.
to 50 gallons, which is as weak as can be effectively used, severe
injury was noted. Insoluble arsenic compounds, such as Paris
green, arsenate of lead, arsenate of calcium and arsenite of zinc
do not damage the trees but are not effective. When the
arsenic is mixed in the sirup the flies do not get enough to
The following plan if carried out thoroughly will very ma-
terially reduce the number of flies and make the growing of
papayas practicable and profitable: (1) Selection of good seed
40 DEPARTMENT OF AGRICULTURE
and production of fruits of oblong shape and thick flesh
which will offer more or less immunity to attack; (2) conscien-
tious destruction of the infested fruits on the trees early in the
season and before the maggots escape into the ground; (3)
destruction of all inferior plants and wild plants around the
place which might serve to breed the pests.
If a planting is sufficiently isolated from other papayas the
flies may be killed out by killing all the plants in the spring,
about April or May and resetting new plants. These new plants
will begin to fruit in the summer or early fall, but there will
be a period of about 60 days when no fruits are present, which
is long enough to starve out the flies. Along with this program
should go the destruction of all wild plants in the hammocks
for a radius of at least 2 miles. One large planting under
observation was kept free from infestation for the entire win-
ter by this method and a good crop of fruit obtained. The
previous winter and spring the plants were badly infested,
but the pests were entirely starved out during the summer.
In most locations, however, a grower would not be sufficiently
isolated to practice this method successfully unless the co-
operation of his neighbors could be enlisted.
If care is taken to select soil that is known to be free from
nematodes (the small microscopic worm that causes root knot)
in which to plant the seed and raise the seedling plants, this
pest will under average conditions, cause but little damage.
If the plants are kept well mulched so as to retain an abun-
dance of soil moisture, nematodes will cause very little injury
to fruiting plants.
The chief disease affecting the papaya is the papaya leaf-
spot. This is a fungus disease that attacks the foliage of the
papaya plants. Black postular spots form on the under surface
of the leaves, while on the upper surface of the leaves brown
To control this disease it is necessary to spray thoroughly
with 4-4-50 Bordeaux. Both the upper and lower surfaces of
the leaves must be sprayed to effect complete control. Make
first spraying at first appearance of the disease and then spray
every two weeks thereafter until the disease is under control.