Papaya

Land Preparation: Papaya

The field should be cleared of bushes, tree stumps and leveled out. Deep soil cultivation is recommended, thus ploughing and harrowing should be done before planting.

Planting: Papaya

1.1. Propagation

Papaya is propagated by seed. In order to  reproduce the desired characteristics,  it is best to get seeds through controlled pollination.  Seeds are extracted from healthy fruits selected from healthy plants. The fleshy outer layer of the seed coat enveloping the seed is removed because it inhibits germination.  This is achieved by rubbing the seed together against a fine-meshed screen under running water.  Thoroughly dried seeds stored in air-tight containers and remain viable for several years.

The seed may be sown directly in the field or nursery beds, seed boxes or polythene bags then transplanted.

 1.1.1 Raising seedlings in seed bed

·         Prepare either raised or sunken beds 1m wide and of convenient length.

·         Water the beds thoroughly before and after sowing until seeds germinate.

·         Sow seeds at a depth of 1cm in rows that are 15 cm apart.

·         Seeds germinate in 2-3 weeks.

·         Continue watering until they are ready for transplanting in containers.

·         Prick out at the 2-3-leaf stage, transferring 3-4 seedlings to each container 1 week after emergence.

1.1.2. Raising seedlings in containers

·         Plants propagated in containers are less susceptible to stress and subsequent loss than those produced in seed-beds.

·         Seeds are sown in small containers (tin cans, plastic bags or paper cups) at the rate of 3-4 seeds per container.

·         Use of sterilized soil minimizes losses resulting from nematodes and damping-off disease.

·         Germination takes 2-3 weeks.

·         Seedlings are transplanted about 2 months after sowing when they reach the 3-4-leaf stage or 20cm height, preferably at the onset of the rainy season.

·         During transplanting, care must be taken not to disturb the roots. Older seedlings recover poorly after planting out.

1.2. 3. Direct Planting

·         Sow 6 seeds per planting hole.

·         Thin to 4 plants after germination and later to 1 plant per hole after it is possible to establish the sex of the plant.

1.2. Field establishment

• Spacing and plant population:  

• 2.5 m x 2.5 m (1,600 plants/hectare)
• 2.5 m x 3 m (1,332 plants/hectare)
• 3 m x 3 m (1,110 plants/hectare)

• Time of seed sowing and transplanting

• September-October and December-January are two suitable times for seed sowing
• Seedlings become ready for transplanting at 40-50 days after sowing
• Transplanting in the field
•  Dig Planting holes of 60 x 60 x 60cm.
• Transplant seedlings to the field 4-5 weeks, when they are 10-20cm in height. Young plants have higher survival rates than older plants.
• Mix 40kg of well rotten manure with 100-120g of DAP and the top soil and fill the hole with the mixture.
• Plant 4 seedlings per hole for varieties that have male and female flowers on different plants.
• Thin to one female or one hermaphrodite plant per hill when the plants reach the flowering stage (after 6-8 months).
• In the absence of hermaphrodite plants, 1 male plant per 25-100 female plants is retained as pollinator. Most of the male plants should be removed since they bear no fruit.
• For hermaphrodite varieties plant 1 seedling per hole.
• Transplanting should be at the same depth as the seedlings were previously growing; deeper planting may cause some loss due to stem rots.
• Plants that have been grown in seed beds should, in addition to being hardened off (reduce irrigation), be provided with some simple cover when transplanted to the growing site.

• It is good practice to reduce the leaf area of the plant at transplanting, so that transpiration is reduced while the root system is re-established. If possible planting should be done in the late afternoon.
• Plants propagated in containers are less susceptible to stress and subsequent loss than those produced in seed-beds. However, these will still require attention until they are established.
• Whichever method is used, seedlings should be planted into moist soil and watered as soon as possible afterwards. Daily watering will be required for some time.

Crop management: Papaya

1.1. Wind break

Papaya do not tolerate strong winds and the establishment of wind breaks hedges is necessary.

1.2. Mulching

This is recommended after sowing or transplanting. The mulching should not be so close to the stem of the seedlings, give an allowance of about 10cm from the stem. The mulch should be removed so that the development of the young plant is not hindered.

1.3. Weed control

Frequent hand weeding is essential and care need to be taken not to damage the roots of the young plants. Keep the area around the stem weed free. Slashing is not enough as the seedlings will still suffer from weed competition.

1.4. Intercropping

Papaya grows best when planted under full sunlight. Intercropping can be done when papaya are young. Low growing annual crops such as capsicums, beans, onions and cabbages are suitable intercrops.

1.5. Manure and fertilizer

Apply manure at the rate of 40kg per tree before the rains begin every year.  It should be applied around the plant basin and incorporated well into the soil.

Apply 40g of CAN per tree two months after transplanting in the first year. If possible apply a split application of 60g CAN per tree at the beginning of the long and short rains. After which 200g of compound fertilizer can be applied per tree per year at the beginning of the rains.

1.6. Fruit thinning

• Most of the papaya varieties bear 2-3 fruits per cluster
• Extra fruits should be thinned out keeping the best one only
• In 2^nd or following years, the plant bears overcrowded fruit. The smaller fruits needs to be pruned

Pests and Diseases: Papaya

1.1. Major Pests

• Fruit flies: the flies usually deposit their eggs in ripe fruit. Developing larvae cause rotting of ripening fruits.

Control: fruit should be harvested at the mature green stage. Over ripe and infested fruit should be buried.

• Red Spider Mites: mites suck the plant sap, leading to poor plant growth and blemishes on the fruit. Serious infestations occur during long dry periods

Control

Use recommended miticides.

• Root-knot nematodes: cause root swellings or root galls, resulting in yellowing and premature abscission of the leaves. Infestation by nematodes reduces growth and yield.

Control: do not replant papaya in the same field.

• Birds: they feed on the ripe fruit.

Control

Harvest when the fruits are physiological mature).

1.2. Major Diseases:

• Damping-off and Foot rot: it is caused by soil-borne fungi, and result to rotting of roots, stem and fruits.

• Seed treatment with Vitavax or Captan @ 2-3 g per kg of seed
• Sterilization of nursery bed by burning saw dust or rice hull (6 cm thick)
• Soil amendment by poultry litter at 5 t/ha
• Solarization of the bed prior to seed sowing
• Drenching of Ridomoil MZ @ 2 g/L
• Ripe fruit rots– Several fungal pathogens are involved in fruit decay.
• Powdery mildew: as the fruits develop, the white mould disappears leaving grey-scarred areas. (Use sulfur based fungicides)
• Papaya ring spot virus (PRSV): this virus is spread by aphids and it is also mechanically transmitted.  Severely infected plants do not flower and they die young. Infected fruits develop characteristic line patterns, which form rings and remain green when fruits ripen. (Destroy infected plants, doo not intercrop with host plants e.g. cucurbits).
• Anthracnose causes fruits to rot and makes them unmarketable.

Papaya mosaic virus

• Yellow patches are appeared on leaves and fruits, bending of petiole and plant growth become stunted
• The disease is transmitted by aphid

Harvesting: Papaya

• Papaya starts flowering after 6-8 months and fruits are ready for harvesting 8-10 months after trees have been planted.
• The physiological development stage of fruit at the time of harvest determines the flavour and taste when the fruit is ripened.
• Fruits harvested too early have longer post harvest life, but give abnormal taste and flavour. Fruits also tend to shrivel and suffer chilling injury when refrigerated.
• Harvest when at least 2 yellow strips appear between the ridges of the fruit.
• Harvest by cutting fruits from the tree, leave a stem 0.5-1 cm long on the fruit. The stem can later be reduced when packing the fruits.
• Avoid latex flowing on the fruit by placing the stalks of harvested fruits facing downwards.
• Place the fruits gently into the harvesting crates.
• It is better to harvest the fruits early and leave them to ripen in shade.

Yields

• Under good conditions fruiting starts within a year from planting and continues with a yield of 30-150 fruits per tree during its life span. A yield of 35-50 ton/ha can be realized per year. The fruits are available throughout the year provided water is adequately available. A pawpaw plantation can be productive for 4-5 years but the economical period is 3-4 years.

Post harvest Management: Papaya

• The fruits should be handled carefully and should not be stored for many days.
• Under ripe fruits may be stored for almost 3 weeks and then removed to room temperatures to complete ripening.
• Fully ripened fruit can only be stored for 2 – 3 days at room temperature.
• 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 10⁰ C), but lower temperatures may interrupt the ripening processes and cause injury;
• 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.