Pawpaw (Carica papaya) production

Land preparation

Pawpaw is widely cultivated fruit tree in the tropics and subtropics. Ploughing and harrowing should be done before planting as deep soil cultivation is recommended. The field should be cleared of bushes, tree stumps and leveled out.

Climatic and soil requirement

Pawpaw grows best in areas below 1500 m above sea level as quality and yield are low at higher altitudes. It requires a rainfall of above of 1000 mm and cannot survive sustained drought. Therefore, irrigation is essential in areas of low rainfall to facilitate vigorous growth. Pawpaw can tolerate any kind of soil provided it is well drained and not too dry as the roots are very sensitive to water logging and even short periods of flooding can kill the plants. However, it requires a light, well-drained soils of pH of 6.0-7.0 and rich in organic matter. Pawpaw thrives in warm to hot areas with adequate rainfall and a temperature range of 21-33°C. Cold temperatures below 120 C cause the tree to grow poorly. Fruit tastes much better during warm sunny seasons, however, during cold periods, fruit ripening can be delayed and fruit quality can be reduced.

Variety selection

For commercial production, it is important to select high yielding varieties. Choose variety as per market demand and environmental adatability. Also, site should be suitable with the required production requirements and market for produce should be readily available since the fruits are highly perishable. Pawpaw variety includes:

• Honey Dew: An Indian variety of medium height that produces oval juicy medium size fruit.
• Kiru- Tanzanian variety that produces large fruits and it’s a high yielder of papain.
• Mountain-This is a variety that grows at high altitudes with very small fruits only suitable for jam and preserves.
• Solo- Hawaiian variety, hermaphroditic and produces small round very sweet fruits with uniform size and shape. It is popular for both export and local markets.
• Solo Sunrise- Another high yielding Hawaiian variety that produces smooth pear shaped fruit of high quality, weighing 400 to 650 grams. The flesh is reddish orange.
• Sunset- Dwarf high yielding Hawaiian variety with red flesh and having same characteristics as ‘Solo’ variety and very sweet.
• Solo sunset- Hermaphrodite fruit having a pear shape, with a small neck at the stem end. Fruit sets at average 1 meter above the ground, red/pink in color and very sweet.  It’s average weight is 425 grams.
• Sunrise (Strawberry pawpaw) – Has a deep red-flesh. Variety is resistant to the ring spot virus disease. It has a deep red-flesh, freckled greenish-yellow skin that turns yellow as the fruit ripens.
• Waimanalo- Hawaiian variety that yields smooth, shiny round fruits with short neck and is of high quality. Fruit surface is orange yellow, thick, sweet and firm and usually commended for fresh market & processing.
• Kapoho- These fruits are smaller than that of sunrise. Solo type with yellow to orange flesh colour.
• Mexican Red- A rose-fleshed pawpaw that is lighter in flavor but not as sweet as Hawaiian type. It is a medium to very large fruit. However, it is not as sweet as Hawaiian types.

Propagation:

Pawpaw is propagated by seed and therefore to reproduce the desired features, it is best to get seeds through controlled pollination. Seeds are extracted from healthy fruits selected from vigorous plants. The surface layer of the seed coat (sarcotesta) enveloping the seed is removed because it inhibits germination. This is done by rubbing seeds against a fine meshed screen under running water. Thoroughly dried seeds stored in air-tight containers remain viable for several years. The seed may be sown directly in the field or nursery beds, seed boxes or polythene bags then transplanted.

Nursery preparation:

In beds

• Prepare either raised or sunken beds 1m wide and of convenient length.
• Beds should be carefully watered before and after sowing until seeds germinate.
• Seeds should be sown 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.

In containers

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

• 3-4 seeds are sown in a small container (tin cans, plastic bags or paper cups).
• Sterilized soil to minimizes losses resulting from nematodes and damping-off disease.
• Germination takes 2-3 weeks and 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.

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.
• Plant 2 seeds per hole and thin to 1 seedling per hole after 1 month for hermaphrodite varieties.

Field establishment

Dig Planting holes of 60 x 60 x 60cm.

Spacing and plant population

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

Transplanting in the field

Seedlings are transplanted to the field 4-5 weeks, when they are 10-20cm in height. Young plants have higher survival rates than older plants. When transplanting,

• Fill the planting hole with a mixture of 40kg of well rotten manure with 100-120g of DAP and the top soil.
• For varieties that have male and female flowers on different plants, plant 4 seedlings per hole.
• When the plants reach the flowering stage (after 6-8 months), thin to one female or one hermaphrodite plant per hole. 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 produce 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 be provided with some simple cover when transplanted to the growing site.
• Leaf area of the plant should be reduced at transplanting to mitigate the evapotranspiration 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 technique is used, seedlings should be cultivated into moist soil and watered as soon as possible afterwards. Daily watering will be required for some time.

Management practices

Wind break

This is necessary as establishment of Paw paws do not tolerate strong wind.

Mulching

This is recommended after sowing or transplanting and later removed so as not to hinder the growth of young plant. Mulching should not be so close to the stem of the seedlings. An allowance of about 10cm from the stem is required.

Weed control

Area of establishment should be weed free so as to avoid competition for soil nutrients Frequent hand weeding is essential and care need to be taken not to damage the roots of the young plants.

Intercropping

Pawpaw can be intercropped with low growing annual crops such as capsicums, beans, onions and cabbages when the pawpaw plants are still young.

Manure and fertilizer

Application of manure and fertilizers should be applied around the plant basin and sunked well in to the soil.

• Apply manure at the rate of 40kg per tree before the rains begin every year.
• 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.

Pest and Diseases

Integrated pest Management is the recommended method for control of pests and diseases that includes good cultural practices, biological and chemical control. Some major pest and diseases of pawpaw are listed in the table below:

Major Pests

Harvesting

Pawpaw 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.

Harvest when at least 2 yellow strips appear between the ridges of the fruit. You can also 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.

Post-harvest handling

Place the fruits gently into the harvesting crates. 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. Fruits harvested too early have longer post-harvest life, but give abnormal taste and flavor. Fruits also tend to shrivel and suffer chilling injury when refrigerated.

Challenges in production

• Lack of quality planting materials.
• Factors such as fungal diseases, physiological disorders, mechanical damage, or a combination of these are the leading causes of post-harvest losses.

Quality fruits can be obtained by ensuring the recommended pre-harvest and post-harvest practices are adhered to.