Papaya (pawpaw)

Crop Details

The following are the crop details for papaya.

  • Scientific name: Carica papaya
  • Local names: Pawpaw
  • Order: Violales.
  • Family: Caricaceae
  • Genus: Carica.

General information

Pawpaw (Carica papaya L.) is a popular tropical American fruit. It is commonly cultivated for its small to large melon-like fruit.

The type of inflorescence produced by papaya trees reflects whether the tree is male, female, or hermaphrodite. Male trees have many flowers on long, pendulous panicles, whereas female trees have solitary flowers or clusters of a few yellow-green flowers.

The papaya fruit is a large fleshy berry with smooth green skin that turns yellow or orange when ripe. The fruit's flesh is thick and succulent, ranging in color from yellow to red or orange. Many black wrinkled seeds are present in the fruit. 

Papaya trees can live for up to 25 years and grow to a height of 2-10 m (6.6-33 ft). To ensure maximum productivity, plantations are typically replaced every three years. 

Papaya, also known as pawpaw, is thought to have originated in the Caribbean region of Central America.




Pawpaw varieties

The following are the most commonly grown pawpaw varieties in Kenya:

Sunrise- produces high-quality smooth pear-shaped fruits weighing 400-650g. 

The flesh of the fruits is reddish-orange, and the variety is prolific.

Mountain- produces small fruits that are only suitable for jam and preserves.

Solo- grows small round sweet fruits that are uniform in size and shape. 

Red royale F1- this is an improved breed that produces high-quality fruits weighing 1.7-2.3kgs, with a red attractive color and a sweet flavor.




Uses

The ripe fruits are high in vitamins C and A, which are frequently lacking in the diets of people living in the tropics. Immature fruits are stewed or boiled as a vegetable in some countries, such as the Philippines.

The unripe fruits of the C. papaya tree contain papain, a substance used commercially as a meat tenderizer. Crumpled leaves are used as a meat tenderizer in Southern Asia before wrapping meats.

Papain also has medicinal and industrial applications, such as tanning leather, preventing wool shrinkage, and keeping beer clear during the brewing process.




Propagation

Basic information

Papaya is a tropical plant that grows best in temperatures ranging from 21 - 33°C in frost-free areas. Papaya can be grown in a variety of soils as long as adequate drainage is provided, but it grows best in light, well-draining soils with a pH between 5.5 and 6.5. 

A monthly rainfall of about 4 inches is required for papaya. Supplemental irrigation should be provided for trees in areas with low rainfall. 

Water-logged soils should be avoided because trees are extremely sensitive to flooding. Papaya trees are also susceptible to high winds, and tall trees can easily topple. Planting should be avoided in windy areas.

Seed propagation

Pawpaw is almost entirely propagated from seeds in commercial cultivation. Seeds may be sown in trays filled with a suitable medium, peat pots, polyethylene bags, or directly in the field. 

Germination occurs in 12-20 days. Seedlings are transplanted into 7.6 cm peat pots or 10 cm plastic bags at the two-leaf (cotyledonary leaves) stage, preferably at the onset of the rainy season. 

Care should be taken during transplanting to avoid disturbing the roots. After planting out. Container-grown seedlings should be gradually hardened in sunlight before being field-transplanted 1.5-2 months after germination, at about 20 cm high and at the 8- to 12-leaf stage. Up to 15-20 seeds are sown in each hole during field planting.

Upon germination, seedlings are thinned out to leave five or six seedlings to grow to flower. At first flowering, a vigorous plant of the desired sex is kept and the others removed.




Cultivation

Site preparation and planting

Field preparation in many areas is poorly done due to lack of appropriate equipment or rough terrain. On heavy or compacted soils, subsoiling or ripping down to 50 cm or more is desirable to allow roots to penetrate deeply. Planting holes 30-45 cm in diameter are best dug with a tractor-mounted soil auger. If there is a chance of flooding, raised beds are used.

After about 6-8 weeks in the nursery, the seedlings should reach the 8- to 12-leaf stage and are most suitable for field planting. In rain-fed areas, field planting is done at the beginning of the rainy season. Seedlings grown in pots and bags are planted directly, with the removal of the pot or bags. Transplanted plants must be watered soon after planting to settle the soil around the root system.

Spacing between plants and between rows varies widely. Universally practiced is the single-row system, with plant spacing ranging from 1.8 to 3 m and between-row spacing varying from 1.8 m to as much as 3.6 m. The between-row spacing largely depends upon the degree of mechanization; a standard tractor requires approx. 3 m. The most frequently used spacing is 2.0-2.5 m within row × 2.5 m, giving a density of 1600-2000 plants/ha. The double-row system, with 2 m between a set of rows and 3.5 m between double rows, is used. Normally, two or three seedlings are planted in each hole, spaced about 30 cm apart.




Pawpaw general care and maintenance 

Weeds are a major source of competition for papaya seedlings, so keep the areas around the trees weed-free. Weeds can be effectively suppressed by a layer of mulch around the plants. 

To meet the nutrient requirements for fruit production, papaya necessitates regular fertilizer applications. Fertilizer is typically applied 2-4 times per year in commercial plantations. In the home garden, 1/4 cup of a balanced fertilizer applied every 14 days is usually sufficient. 

The amount of fertilizer should be increased as the trees mature. When the trees are 7 to 8 months old, 1-2 pounds of complete fertilizer should be applied every 2 months.

Papaya trees should be watered regularly, particularly during hot, dry periods. Papaya trees do not require pruning but it is good practice to remove any dead leaves from the tree. 

Harvesting

Papaya fruits typically take 22-26 weeks to mature. The fruits can be picked when one-fifth of the fruit surface has turned from green to yellow, but leaving them on the tree longer increases the fruit's sugar content. Fruit can be twisted or snapped off the tree, or it can be cut using a sharp knife.




References

CABI Crop Protection Compendium. (2008). Carica papaya (papaw) datasheet. Available at: http://www.cabi.org/cpc/datasheet/13392. [Accessed 03 March 15]. Paid subscription required. Crane, J. H. Papaya growing in the Florida home landscape. University of Florida IFAS Extension. Available at: https://edis.ifas.ufl.edu/pdffiles/MG/MG05400.pdf. [Accessed 03 March 15]. Free to access. Nishina, M., Zee, F., Ebesu, R., Arakaki, A., Hamasaki, R., Fukuda, S, Nagata, N., Chia, C. L., Nishijima, W., Mau, R. & Uchida, R. (2000). Papaya production in Hawaii. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Available at: http://www2.ctahr.hawaii.edu/oc/freepubs/pdf/F_N-3.pdf. [Accessed 03 March 15]. Free to access. Ploetz, R. C., Zentmyer, G. A., Nishijima, W. T., Rohrbach, K. G. & Ohr, H. D. (eds) (1994). Compendium of Tropical Fruit Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopapspress/Pages/41620.aspx. Available for purchase from APS Press.

Papaya (pawpaw) | Diseases and Pests, Description, Uses, Propagation. (n.d.). Papaya (Pawpaw) | Diseases and Pests, Description, Uses, Propagation. Retrieved February 3, 2023, from https://plantvillage.psu.edu/topics/papaya-pawpaw/infos

CABI. (n.d.). https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.13392. (n.d.).




Common Pests and Diseases

Diseases

Category : Fungal

Anthracnose and charcoal spot Colletotrichum gleosporoides

Symptoms

Small water-soaked lesions of fruit during ripening; circular sunken lesions with light brown margins.

Cause

Fungus

 

Is caused by Glomerellacingulata, primarily infecting the fruit. The disease appears as small water-soaked circular spots that enlarge into brown-black sunken lesions as the fruit ripens. Fungicidal sprays can control this disease. A 20-minute hot-water dip (45°C) reduces post-harvest decay. 

Comments

Fungi spread by wind and rain; disease emergence favored by high temperature and humidity; disease can have a serious impact on refrigerated fruit for export.

Management

Appropriate protective fungicides should be applied; dipping fruits in hot water at 48°C for 20 minutes reduces the incidence of the disease.

Black rot Mycosphaerella caricae

Symptoms
Black sunken rot on young fruits originating from stem end or contact with a leaf; young fruit withering and dropping from plant; small, brown sunken lesions with light brown margins on ripening fruit.
Cause
Fungus
Comments
Fungi enters fruit through wounds.
Management
Appropriate protective fungicides should be applied; dipping fruits in hot water at 48°C for 20 minutes reduces the incidence of the disease.

Black spot Asperisporium caricae

Symptoms
Circular water-soaked or brown lesions on older leaves; centers of lesions become bleached as they mature; leaves curling and turning brown; raised lesions on trunks; sunken circular lesions on fruit.
Cause
Fungus
Comments
Disease spread by wind and rain; disease emergence favored by cool weather interspersed with moisture from dew or rain.
Management
Disease may require applications of appropriate fungicides for adequate control.

Cercospora black spot Cercospora papayae

Symptoms
Tiny black dots on fruit which enlarge to 3 mm across; spots are slightly raised and although indistinct on unripe green fruit, become visible on ripening to yellow; lesions on leaves are irregular in shape and gray-white in color; if infestation is severe, leaves may turn yellow and necrotic and drop from plant.
Cause
Fungus
Comments
Disease usually enters orchard from infected papaya leaves in adjacent orchards.
Management
Applications of appropriate protective fungicides at intervals of 14 to 28 days provide satisfactory control of the disease.

Powdery mildew Oidium caricae-papayae
Other fungi species

Symptoms
Infect all parts of tree. The infected leaves show white mycelial growth commonly on under surface , particularly near leaf veins. Some time white mycelial growth can also seen on upper leaf surface. The infected area becomes light green and chlorotic (lesions) with dark green margin.
Cause
Fungus
Comments
Powdery mildew pathogens are saprophytic need living host for survival and growth. The pathogen is favored by high humidity and low sunlight.
Management
Remove the infected parts and dispose them properly. Avoid irrigating the trees by sprinkler. Provide proper nutrition to trees to withstand powdery mildew infection. If the disease is severe, apply suitable fungicides.

Category : Bacterial

Bacterial canker and decline Erwinia spp.

Symptoms
Angular water-soaked lesions on leaves; lesions coalesce and spread along leaf veins; witling leaves, particularly at top of canopy; water-soaked lesion and cankers on stem; cankers girdle stem and cause plant to collapse; small water-soaked lesions on green fruit.
Cause
Bacteria
Comments
Bacteria survive in lesions and cankers.

Internal yellowing Enterobacter cloacae

Symptoms
Flesh of ripe fruit discolored yellow; discolored areas soft with spreading margins; rotting odor.
Cause
Bacterium
Comments
Disease found in Hawaii.
Management
Dipping fruits in hot water at 48°C for 20 minutes reduces the incidence of the disease and is currently the only method of control.

Category : Viral

Bunchy top Likely caused by Rickettsia bacteria

Symptoms
Chlorosis of young leaves; water-soaked spots on petioles and stems; petioles rigid, horizontal and shortened; thickened leaf blades that cup downward; internodes shorten and growth stops resulting in a bunchy appearance to the plants.
Cause
Bacteria
Comments
Transmitted by leaf hoppers.
Management
Use of tolerant varieties of papaya is currently the only method of control recommended.

Papaya ringspot Papaya ringspot virus (PRV)

Symptoms
Dark green rings on fruit which may be slightly sunken and become less distinct as the fruit ripens; fruits may have uneven bumps; leaves often exhibit a bright yellow mosaic pattern and new leaves are small and plant growth is stunted.
Cause
Virus
Comments
Virus is transmitted by several aphid species.
Management
Infected plants should be removed and destroyed to prevent spread of the virus; new planting materials should be free of the virus; intercropping papaya with a non-host such as corn can help to reduce the incidence of the disease in papaya orchards by providing aphid vectors with an alternative feeding site.

Category : Oomycete

Phytophthora fruit rot (Stem rot) Phytophthora palmivora

Symptoms
Water-soaked lesions on unripe fruit that oozes latex; withering fruit; water-soaked lesions on leaf scars of fruit bearing stem; mature fruit covered in white mycelium.
Cause
Oomycete
Comments
Fungi survive in soil and enter through wounds in stem; disease often emerges after hurricane damage.
Management
Disease can be controlled through the use of appropriate protective fungicides such as mancozeb or copper sulfate; root rot in seedlings can be prevented by planting in holes filled with soil in which papaya has never been grown - by the time the roots extend out of the added soil the plant is no longer susceptible to the disease.

Pests

Category : Insects

Papaya mealybug Paracoccus marginatus

Symptoms
Flattened oval to round disc-like insect covered in cottony substance on tree; chlorosis, plant stunting, leaf deformation, early leaf and fruit drop insects attract ants which may also be present; insect colony may also be associated with growth of sooty mold due to fungal colonization of sugary honeydew excreted by the insect.
Cause
Insect
Comments
Insects have a wide host range; often tended by ants which farm them for their sugary honeydew secretions; transmit Cocoa swollen shoot virus.
Management
Mealybugs can potentially be controlled by natural enemies such as lady beetles but are commonly controlled using chemicals; chemical pesticides may also decrease populations of natural enemies leading to mealybug outbreaks.

Scale insects (White peach scale) Pseudaulacaspis pentagona

Symptoms
Scale insects cause damage by feeding on twigs, branches and fruit, injecting toxins into the plant as they do so; if the infestation is heavy, gumming may occur on the bark and twigs or entire branches can be killed; insects are flattened discs, or "scales" with no visible legs; scales produce a white waxy coating which eventually turns black (black cap stage).
Cause
Insect
Comments
Scale insects overwinter in the black cap stage; winged adult males mate with females which retain their eggs inside the body until they hatch.
Management
Populations are often kept in check by natural enemies, including predacious beetles and some wasps - although broad-spectrum insecticides may result in outbreaks of scale by killing off populations of beneficial insects; trees can be sprayed with horticultural oils when dormant which effectively kill scales without damaging natural enemies.
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