Publication
from Crop Knowledge Master, University of Hawaii, Extension Service
by Chia, C. L. et. al. and Tripton, T. V., et. al.
Papaya
Other Names: Pawpaw, Mikana, Milikana, Papaia, He’i
FAMILY: Caricaceae
SCIENTIFIC NAME: Carica papaya L.
ORIGIN: American tropical lowlands
Description
Papaya is a short-lived perennial growing to 30 ft (9.14 m)
high. Its hollow, herbaceous stem is usually unbranched. The deeply
lobed, palmate leaves are borne on long, hollow petioles emerging from
the stem apex. Flowers occur in leaf axils. Older leaves die and fall
as the tree grows.
Papaya flowers are fragrant and have five
cream-white to yellow-orange petals 1 to 2 in (2.5 to 5.1 cm) long. The
stigmatic surfaces are pale green, and the stamens are bright yellow.
Papaya
fruits are smooth skinned. They vary widely in size and shape,
depending on variety and type of plant. Hermaphrodite plants of
commercial 'Solo' varieties in Hawaii usually produce fruits that are
pear shaped and weigh approximately 12 to 30 oz (340 to 851 g). Female
plants of 'Solo' varieties produce round fruits. Other papaya varieties
produce variously shaped fruits, which may weigh up to 20 lb (9.1 kg).
The fruits usually contain many seeds surrounded by a smooth yellow to
orange-red flesh that is sweet in good varieties.
Flower type.
Flower type is determined by the presence or absence of functional
stamens (male parts) and stigma and ovary (female parts). Within
varieties, flower type is usually identified by flower size and shape.
Female
flowers are relatively large and rounded at the base. They have a
stigma but lack stamens. They generally must receive pollen in order to
set fruit. Pollen can be carried by wind or by insects.
Male flowers
are thin and tubular. They have perfect structure (i.e., they contain
both male and female organs), but the small, vestigial ovary is
nonfunctional. Male flowers are usually borne on a long flower stalk
(peduncle).
Hermaphrodite flowers are intermediate between female
and male flowers in size and shape. They are less bulbous than female
flowers, but not as thin as male flowers. They have perfect structure
with functional stigma and stamens and usually are self-pollinating.
Plant type. Three types of plants are recognized based on flower type: female, hermaphrodite, and male.
Female
plants always produce female flowers. If no male or hermaphrodite
plants are nearby to provide pollen, female plants usually fail to set
fruit. Unpollinated female plants occasionally set parthenocarpic
fruits, lacking seeds.
Male plants are distinguished by their long
flower stalks bearing many flowers. Usually they do not produce fruit,
but on rare occasions there is female expression in the flowers, and
they may set fruits.
Hermaphrodite
plants tend to produce selfpollinated seeds, which result in relatively
uniform progenies. Seeds from hermaphrodite plants of 'Solo' varieties
characteristically produce one-third female and two-thirds
hermaphrodite plants, but no male plants are produced.
Although
hermaphrodite and female plants have similar fruit texture and quality,
female plants may be less productive, and the round female fruits are
marketed only in small quantities in Hawaii as direct sales from
growers to consumers. Female plants are removed from commercial
orchards as soon as they can be distinguished at flowering. In home
gardens, female plants may be kept if hermaphrodite or male plants are
nearby to serve as a pollen source.
Varieties
The
'Solo' variety is valued for its productivity, uniform fruit shape and
size, and excellent fruit quality. 'Solo' strains are predominantly
self-pollinated and thus are highly inbred and uniform.
Three
'Solo'-type varieties are grown commercially in Hawaii. The most
important is 'Kapoho', which has yellow-orange flesh and fruits that
weigh 12 to 22 oz, considered an ideal size for export. 'Kapoho' is
adapted to the Puna district of the island of Hawaii, where
approximately 90 percent of the state's papayas are grown. The
'Sunrise' variety, commercially grown primarily on Kauai, has
reddish-orange flesh and larger fruit than 'Kapoho'. 'Sunrise' is grown
and marketed on a large scale overseas, but in Hawaii its production
and export are small compared to those of 'Kapoho'. The 'Waimanalo'
variety, which has yellow-orange flesh and somewhat larger fruit than
other 'Solo' papayas, is grown and marketed almost entirely on Oahu.
Uses
Ripe
papaya is usually consumed fresh as a breakfast or dessert fruit; it
can also be processed and used in a variety of products such as jams,
fruit juices, and ice cream. Papaya is also consumed as a dried fruit.
Culled fruits can be fed to pigs and cattle.
Papaya is an ingredient
in a variety of cuisines throughout the world. Unripe fruits and leaves
are consumed as vegetables. Papaya seeds are also used as an ingredient
in salad dressings.
Papain is a milky latex collected by making
incisions in unripe papayas. The latex is either sun-dried or
oven-dried and sold in powdered form to be used in beer clarifiers,
meat tenderizers, digestion aids, wound debridement aids,
tooth-cleaning powders, and other products. The ‘solo’ papaya is not a
good variety for papain production due to its low yield of papain.
The
papaya fruit is about 88.8% water, 9.8 % carbohydrate, 0.8% fiber, 0.6%
protein, 0.6% ash and 0.1% fat. A 100g (3.5 oz.) serving of papaya has
39 calories, compared to banana's 92 calories. Papayas also contain 16%
more vitamin C than oranges and are a good source of vitamin A (about
half of that contained in mango). Consumption of the fruit is reported
to aid digestion because of the papain content.
Propagation
Papaya
is grown from seed. Dry seed may be stored for a year or more in
airtight refrigerated containers. Fresh seeds will usually germinate in
10 to 14 days. Germination can be improved by removing the gelatinous
outer seed coat (sarcotesta) before drying.
Seeds are sown
either in containers or directly in the ground. Transplanting
container-grown plants is usually limited to areas where there is
dependable rainfall or supplemental irrigation. When direct-sowing, 10
to 15 seeds are sown 1/4 to 1/2 in (63 to 127 mm) deep in each planting
hole. To ensure adequate stands in lava lands, approximately 0.5 cubic
feet (14.16 cubic dm) of soil should be placed in each planting hole.
The soil helps to retain fertilizer nutrients and moisture.
Soil Types and Location
Papaya
grows well on many types of soil, but they must be adequately drained.
Restricted soil drainage promotes root diseases. Most commercial
production in Hawaii is on porous aa lava. Production on other soil
types is limited to low rainfall areas where restricted drainage is
less likely to cause problems. Heavy clay and pahoehoe lava soils
should be avoided. Soil pH near neutral (pH 6.0 to 7.0) is preferred.
Soil
categories used for commercial production vary from island to island.
On Hawaii, both aa lava and soils are used. On aa lava lands,
additional soil is usually brought in and placed in the planting hole.
The soils used for papaya on the island of Hawaii have a high preplant
phosphorus fertilizer requirement. These soils, as well as the organic
soils derived from lava, are usually acidic, and liming may be
necessary. On Kauai the soils used for papaya usually require
liming and high levels of phosphorus fertilization. On Oahu the soils
on which papaya is grown are often poorly drained.
Papaya grows
best in warm areas below 500 ft (152 m) elevation. Fruit production and
quality decline at higher elevations, where cooler temperatures cause
flower drop and cat-faced (carpelloidic) fruits. (Carpelloidy is the
abnormal development of stamens into fleshy structures.)
Papaya can
tolerate moderate winds if well rooted. Forty to 60 in (102 to 152 cm)
of rainfall evenly distributed throughout the year is adequate for
growth. With higher rainfall, soils should be porous and well drained.
Planting on slopes or on raised hills helps to prevent waterlogging.
Cultural Practices
Seedlings
are thinned to five or six plants per hole six weeks after planting.
Six weeks later, three vigorous seedlings per hole are selected, and
the others are removed by cutting them off at ground level. When flower
buds appear five to seven months after planting, the female plants can
be distinguished and removed, keeping one hermaphroditic plant per
hole. Tree spacing varies from 5 to 7 ft (1.52 to 2.13 m) between
plants in rows 8 to 11 ft (2.44 to 3.35 m) apart.
Fertilizer
schedules vary with soil type, climate, and season. The general
suggestions for fertilizer applications given here are based on
commercial practices but can be used by the home gardener. In
commercial plantings, fertilizers are either broadcast onto the soil
surface within the leaf drip zone or applied through drip irrigation
lines. In home gardens, fertilizers are usually broadcast on the soil
surface. Organic matter mixed with the soil before planting and applied
afterward to the soil surface as mulch helps to ensure good rooting
conditions and a supply of micronutrients.
Preplant fertilizer
applications. On acid soils with a pH of less than 5.5, a preplant lime
application is usually recommended to raise the pH and provide calcium.
Dolomite, which provides both calcium and magnesium, may be substituted
for part of the lime requirement. These soil amendments should be
thoroughly mixed with the soil in the rooting zone before planting.
Phosphorus
applied before planting should be thoroughly mixed with the soil or
placed in a band away from the seeds. Application rates depend on soil
type. For soils that do not have a high phosphorus requirement, a
preplant application of 4 oz (113 g) of 0-46-0 per planting hole is
recommended.
Preplant applications of complete fertilizers are
usually not necessary when planting papaya, because the developing
seedlings can initially use nutrients stored in the seeds. Soluble
fertilizers placed in the planting hole may burn the roots and make
them susceptible to root rots. Slow-release fertilizers generally do
not burn roots when mixed with the soil, and in commercial practice
they are applied on the soil surface when the seeds are planted.
Postplant
fertilizer applications. Moderate applications of slow-release
fertilizers are recommended during the first few months of growth.
Commercial growers apply 0.5 oz (14 g) of slow release fertilizer per
hole at planting and again six weeks later. Postplant fertilizer
applications usually begin three months after planting with rates
increasing with plant size. Maximum rates are applied at five- to
eight-week intervals after the plants begin to flower. A typical
application schedule with a fertilizer such as 14-14-14 begins with 4
oz (113 g) per plant per month during the third through fifth months
after planting. This rate increases to 6 oz (170 g) every five weeks
after the sixth month.
During winter months, when growth and
fruit production are slower, quantities of fertilizer applied should be
reduced. In the absence of rain or irrigation, repeated fertilizer
applications can lead to buildup of undissolved fertilizers, which may
release high concentrations of nutrients into the root zone with the
next rainfall. Excessive N will cause excessive vegetative growth and
is also believed to contribute to soft-fruit problems.
Papayas
planted in replant fields often succumb to diseases caused by
accumulation of soil-borne pathogens. A fallow period of three to five
years may help to avoid the replant problem. Preplant soil fumigation
is an alternative to the fallow period. On lava soils, the "virgin
soil" technique can be used. Soil is collected from land where papayas
have never been grown, and approximately 0.5 cubic feet (14.16 cubic
dm) of soil is placed in holes that are at least 1 ft (30.5 cm) in
diameter and 4 to 6 in (10.2 to 15.2 cm) deep.
For best growth
of young plants and good yields of bearing plants, papayas should be
irrigated as necessary to supplement rainfall. When rainfall is
limited, commercial growers may apply up to 10 gal (37.851) of water
per tree per day to bearing trees. Yields can also be increased by good
weed control practices.
Harvest and Postharvest
Papaya
fruit should be harvested after color break - when some yellow shows on
the fruit - but before fully yellow (about 9 to 14 months after
planting). Fruit for home consumption is best harvested when half
yellow. If left to ripen on the tree, the fruit is often damaged by
fruit flies and birds.
When papaya plants are short, fruits can
be harvested by hand while one is standing on the ground. As the plants
grow taller, harvesting aids are required. One technique uses a
modified plumber’s helper to snap the papaya from the stem. The fruit
is caught before it falls to the ground. One person can harvest about
800 to 1000 pounds per day with this technique. Another technique
involves a platform rigged to a tractor, which lifts the workers. This
method requires flat terrain.
To be certified for shipment, fruit for export must be harvested and packed in strict compliance with quarantine regulations.
Harvested
fruit is ripened at room temperature and refrigerated when fully ripe.
When ready to eat, fruit is usually partially to fully yellow and
slightly soft; refrigeration can extend its storage life for several
days. In commercial situations, the storage life of partially ripe
fruit can be extended for up to two weeks by holding it at about 50 F
(10 C), but lower temperatures may interrupt the ripening processes and
cause injury; the optimal storage temperature for fully ripe fruit is
about 36 F (2.2 C).
Papayas must be treated to kill any eggs or
larvae of fruit flies that may be present in the fruit. Treatments
include double-dip hot water treatments and vapor heat treatments. The
double-dip treatment may lose certification for papayas destined for
the U.S. mainland. A dry heat treatment has been approved and awaits
certification.
Diseases
Anthracnose and chocolate spot, Colletotrichum gloeosporioides (fruits, petioles)
Phytophthora, Phytophthora palmivora (fruit, stem, roots)
Powdery mildew, Oidium caricae (leaves)
Black spot, Cercospora papayae (fruit)
Damping off, Pythium, Phytophthora, Rhizoctonia (seedlings)
Wet rot, Phomopsis sp. (fruit)
Dry rot, Mycosphaerella sp. (fruit)
Watery fruit rot, Rhizopus stolonifer
Stem-end rot, Botryodiplodia theobromae, Mycosphaerella sp., Rhizopus stolonifer, Phomopsis sp. (mature fruit)
Papaya ring spot virus (formerly referred to as papaya mosaic)
Reniform nematodes, Rotylenchulus reniformis
Root-knot nematodes, Meloidogyne spp.
Insects
Stevens leafhopper, Empoasca stevensi
Mediterranean fruit fly, Ceratitis capitata
Melon fly, Bactrocera cucurbitae
Oriental fruit fly, B. dorsalis
Mites
Broad mite, Polyphagotarsonemus latus (seedlings, young plants, lower surface of young leaves)
Red and black flat mite, Brevipalpus phoenicis (fruit)
Tuckerellid mites, Tuckerella ornata, T. pavoniformis (trunks of old plants)
Carmine spider mite, Tetranychus cinnabarinus (lower surface of mature leaves)
Citrus red mite, Panonychus citri (upper surface of mature leaves)
Texas citrus mite, Eutetranychus banksi (upper surface of mature leaves)
Production
Papaya
trees bear fruit throughout the year. "Skips" in the fruit column
caused by temporary sterility may occur during hot, dry summer periods
and may cause fruit shortages in winter.
The plants will
continue to bear for many years, but yields usually decline as the
trees age, and picking becomes difficult. In commercial production,
fields are usually replanted or abandoned after three years.
Papayas
marketed in or exported from Hawaii are regulated by a Federal
Marketing Order that sets fruit size and quality requirements.
In
the United States, Hawaii is the major producer and supplier of papaya,
with 2500 acres in 1989. It is also estimated that there were 350 acres
of papaya grown in Dade County, Florida in 1987-1988.
The United
States also imports papaya from foreign countries. In 1989, the United
States imported 6 million lb of fresh papaya at a CIF (cost, insurance,
and freight) value of $1.1 million. Mexico was by far the largest
supplier, with 76% of the total. Other major suppliers were the Bahamas
(9.7%) and the Dominican Republic (7.5%).
Production of papaya
(fresh and processed) in Hawaii in 1989 was almost three times that in
1972. Storms affected the production in 1979 and 1985. Poor weather,
disease, and Hurricane Iwa contributed to the decline in production in
1982.
Most of the commercial papaya production is in Puna on the
Big Island. In 1989, about 97.4% of the papaya was produced on the Big
Island, followed by Kauai (1.3%), Oahu (1.1%), and Maui and Molokai
(0.2%).
The 1989 market supply of fresh papaya for the state of
Hawaii was 18.8 million lb. The major market was Honolulu (78.2%),
followed by the Big Island (10.1%), Maui and Molokai (8.5%), and Kauai
(3.2%).
During 1989, 44.6 million lb, or 70% of Hawaii's
production of papaya for the fresh market, was exported out of state.
The primary overseas destinations were the US mainland (26.6 million
lb), Japan (14 million lb), and Canada (4 million lb). The major
markets on the US mainland were Los Angeles (61.4%), San Francisco
(10%), and New York City (9.4%). The average wholesale prices for
Hawaii papaya in these markets were $0.975/lb, $1.15/lb, and $1.18./lb,
respectively.
In 1992, the total farm gate value of papaya in
Hawaii was $14.4 million for the 71,300,000 lb harvested from 259
farms. A total of 55,800,000 pounds of the harvested papaya was
consumed as fresh fruit, while 15,500,000 pounds was processed. The
average farm gate price of papaya for the fresh market was 25.0 cents
per pound. The average farm gate price for processed papaya was
considerable lower at 3.0 cents per pound. The total value of utilized
production was $14,415,000.
Currently, papaya ringspot virus is
a serious problem for growers on Oahu and the Big Island. There is no
cure for the disease at this time and the only method of control is
prevention. This disease may affect papaya production in the State of
Hawaii detrimentally.
References
Chia,
C. L., M. S. Nishina, and D. O. Evans. 1989. Papaya. Commodity Fact
Sheet PA-3(A) Fruit. Hawaii Cooperative Extension Service, CTAHR,
University of Hawaii.
Neal, Marie C. In Gardens of Hawaii. Hawaii: Bishop Museum Press, 1965.
Tipton,
Trace V., Kevin M. Yokoyama, Kulavit Wanitprapha, Stuart T. Nakamoto
and C. L. Chia. 1990. Papaya Economic Fact Sheet #10. Department of
Agricultural and Resource Economics, CTAHR, University of Hawaii.
Statistics
of Hawaiian Agriculture 1991. Prepared by: Hawaii Agricultural
Statistics Service, PO. Box 22159, Honolulu, Hawaii, 96823-2159.
December 1992. 105 pages.
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