Papaya

PAPAYA (Carica papaya L.)

This crop is found in almost all tropical & sub-tropical countries of the world.
Importance

•    Nutrition:- vitamins A & C
•    Processing or consumed fresh
•    Used for tenderizing meat
•    Chill proofing beer /
•    Industrial use in manufacture of drugs for stomach ailments
•    Seeds are used to make stomach cures
•    Fruits are livestock feeds
•    Processing juice and jam
Varieties
•    Solo papaya
•    Mountain papaya
•    Sunrise papaya
•    Sweet papaya

Brief Botany

•    It is a herbaceous single stem tree with a potential of growing up to a height of 9 meters
•    It is semi-woody and hollow inside and usually non-branched, unless it is damaged at the growing tip during 0 – 10 years of age
•    Economic yields are achieved from the 1st year up to the 4th year, beyond which the yields are poor
•    It has 3 types of flowers depending on the sex of the tree.  Male trees produce male flowers.  Sex of male tree flowers is unstable under normal circumstances but in cold conditions, there is reversal of sex to form female flowers.  In other words, manifestation of sex in male trees depends on season.  Female trees are stable i.e. they do not reverse irrespective of the season.  Hermaphrodite trees are unstable in their sex expression.  Under hot / high temperatures they tend to maleness and produce teratological fruits as a result.  The female flowers produce a rounded/spherical fruit.  Hermaphrodite fruit is usually elongate.  Under different temperature conditions, they also form different elongate shapes that are deformed.

Ecological requirements

•    Latitude 32 ºN to 0 – 3S ºS (purely tropical and sub-tropical crop)
•    Altitude 0 – 1500 meters above sea level
•    Temperature 22 - 26 ºC
•    Soil PH range is 6 – 7.  This avoids problems of  Calcium deficiency which when present depresses growth and fruit set and enhances fruit drop
•    Soil must be deep fertile and well drained.  The soil also have a good water holding capacity because turgidity of the plants is dependent on the amount of soil water provided.
•    Require adequate water supply since the tree cannot withstand water stress since it is a soft wooded plant
Cultural requirements
•    Sex of papaya cannot be easily determined at younger stages.  Therefore, when transplanting, start with 3 – 4 seedlings, then leave them to mature until they flower
•    Planting hole should be between 45cm3 to 60 cm3 since papaya is a heavy feeder.
•    Spacing: 2 – 2.5 by 3metres is adequate since papaya is  single-stemmed and roots do not extend far
•    Fertilization:  Being a heavy feeder, put 1 debe of well decomposed organic manure per planting hole in addition to a phosphate fertilizer e.g. Double Super Phosphate (DSP), at 100 – 120grams.  Nitrogenous fertilizers e.g. CAN should be preferably applied later on when the plants are already established.  This can be done at a rate of 200g/plant/year.
•    The papaya trees require protection from strong wind which may cause breakage of these plants.
•    The field should be kept free from weeds
•    Mulching may be done to conserve moisture content of the soil
•    Intercropping: Papaya grows best when planted in full sunlight. However, it can be planted as an intercrop under coconut, or as a cash crop between young fruit trees such as mango or citrus. Low growing annual crops such as capsicums, beans, onions and cabbages are suitable good intercrops.
•    When fruits are mature when the skin colour for fruits start changing from green to yellow/green.  Also the flesh changes from white to yellow.  At this point the Brix content is at 11.5%.  Brix increases with maturity, reaching maturity at a certain point and beyond overripenning, it declines.  Very low brix is also influenced by excessive rainfall/irrigation water and exposure to excessively low temperatures
•    Yields per tree vary from 30 to 150 fruits annually, giving 35 to 50 tons of fruit per ha per year. A papaya plantation can be productive for over 10 years but the economical period is only the first 3 - 4 years. It is therefore advisable to renew the plantation every 4 years.

Pests and diseases

Pests:  aphids, thrips, mites, fruit flies
 Proper pest control measures should be utilized.  A pest such as aphids transmits Papaya Ringspot Virus PRSV, an economic disease in papaya production.  Proper pesticides (both contact & systemic) should be utilized.
Diseases

Damping-off and root rot: - Stem and fruit rots are produced on papaya.   Plants are susceptible at all ages but roots of young seedlings are most susceptible. Good soil aeration, Good drainage and hygiene are important to control these fungi in the orchard as well as in the nursery. Copper based fungicide treatments at the very beginning of first symptoms can reduce fruit rots. However, it is very sensitive to copper fungicides

Papaya ringspot virus (PRSV):  Characterized by yellowing and stunting of crown, Mottling of leaves, small darkened concentric rings on the fruits, shoe stringing of young leaves.  Has no cure but to avoid having in the orchard, control aphids.

Powdery mildew (Oidium caricae; Sphaerotheca humili):- Young crown leaves show light green patches covered by a white powdery growth. Fruits develop circular, white patches on the surface. As the fruits develop, the white mould disappears leaving grey-scarred areas.  Fungicides such as Ridomil and Bayleton effectively control this disease.