PAWPAW PRODUCTION

PAWPAW (Carica papaya)

Introduction

Pawpaw is widely cultivated fruit tree in the tropics and subtropics. It is grown in Kenya as a domestic fruit and small-scale cash crop. The fruits are low in calories and rich in vitamins A, B1, B2 & C, iron and potassium. Papayas enzymes promote digestion easing constipation. Sale of fresh papaya provides regular income for farmers since the fruits are produced through out the year.  

Utilization

Pawpaw fruits are sold and eaten locally as fresh fruit, with high demand from the hotels, local grocery, fruit salad vendors, supermarkets and export market. The fruits are dried and exported as part of a dried fruit mixture.

It can be used to make ice-cream flavour, refreshing drinks, jam, jelly, wine, marmalade, candies and crystallized fruits.

The latex produced by the unripe fruit is harvested and used in the production of papain, used in the brewing industry, canned meats and pharmaceutical industries.

Green fruits are pickled or cooked as a vegetable.

Young leaves are sometimes eaten as vegetables.

Potential for Pawpaw farming

Pawpaw production can be very profitable and rewarding for a farmer even on a small parcel of land. There are a number of processing opportunities for the fruit and export market.

Tree types

The pawpaw has three tree types based on the flowers are arranged; female, male and hermaphrodite. These can only be differentiated after it flowers. The characteristics are described below:

Pistillate (Female plants)

They produce female flowers only. These are large, situated singly or in clusters near the trunk of the tree and close to the base of the leaf stalk. There are no stamens (Male flowers), so cross pollination is necessary for the fruit to set. They produce good fruits.

Staminate (Male plants)

They produce only male flowers, which are borne in large numbers in long, drooping branches of up to 1m in length. The true male flower produces pollen only and it is essential for the development of fruit from the female flower. Occasionally male plants will produce 2 hermaphrodite flowers and set fruit on the ends of the branches; however, these fruits are usually of poor quality or no fruit production.

Hermaphrodite plants

They produce flowers which have both male and female parts and are capable of self- pollination. Bisexual fruits are usually long and narrow, and although the eating quality may be excellent, the shape presents some problems for commercial handling.

Pollination

Pollination is a key component of productivity that also plays a role in determining fruit set and fruit quality. Hence it is important to balance the tree types.

Varieties

Most of commercial varieties grown in Kenya are derived from Hawaii. A few are from India and some known as 'Mountain varieties'.

Honey Dew -This is an Indian variety of medium height that produces oval juicy medium size fruit.

Kiru- This is a Tanzanian variety that produces large fruits.

 It is 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- This is a Hawaiian variety that produces small round very sweet fruits with uniform size and shape. It is hermaphroditic. It is popular for both export and local markets.

Solo Sunrise- Hawaiian variety that produces smooth pear shaped fruit of high quality, weighing 400 to 650 grams. The flesh is reddish orange. This variety is high yielding.

Sunset- Hawaiian variety is a dwarf high yielding plant with red flesh and having same characteristics as ‘Solo’ variety. It is very sweet

 Solo sunset- The fruit is red/pink in color and very sweet. Average fruit size is 425 grams. Hermaphrodite fruit is pear shaped, with a small neck at the stem end. Fruit sets at average 1 meter above the ground.

Sunrise (Strawberry pawpaw) - Has a deep red-flesh. Variety is resistant to the ring spot virus disease. Fruit has a freckled greenish-yellow skin that turns yellow as the fruit ripens.

Waimanalo- Hawaiian variety that produces smooth, shiny round fruits with short neck and is of high quality.The flesh is orange yellow, thick, sweet and firm. It is recommended for fresh market & processing.

Kapoho- Solo type with yellow to orange flesh colour. Fruits are smaller than that of sunrise.

Mexican Red- A rose-fleshed pawpaw that is lighter in flavor. It is a medium to very large fruit. However it is not as sweet as Hawaiian types

Ecological Requirement

Altitude

They grow best in areas below 1500m above sea level. The quality and yield are low at higher altitudes.

Rainfall

Evenly distributed annual rainfall of above 1000mm. Pawpaw trees cannot withstand prolonged drought. In low rainfall areas irrigation is necessary to facilitate vigorous growth.

Soils

Pawpaw grows best in light, well-drained soils rich in organic matter with soil pH of 6.0-7.0. It can tolerate any kind of soil provided it is well drained and not too dry. The roots are very sensitive to water logging and even short periods of flooding can kill the plants.

Temperature

Pawpaw thrives in warm to hot areas with adequate rainfall and a temperature range of 21-33°C. Fruit tastes much better during warm sunny seasons. Cold temperatures below 120 C cause the tree to grow poorly. Frost can kill the plant; Cool and overcast weather delays fruit ripening and depresses fruit quality.

Starting Production

·         Variety selection-For commercial production, it is important to select high yielding varieties

·         Choose variety as per market demand and environmental adatability.

·         Site should be suitable with the required production requirements

·         Market for produce should be readily available since the fruits are highly perishable.

Land preparation

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.

Propagation

·         Pawpaw is propagated by seed. 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 (sarcotesta) 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 remain viable for several years.

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

·         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.

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.

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.

·         For hermaphrodite varieties, plant 2 seeds per hole and thin to 1 seedling per hole after 1 month.

Field establishment

Dig Planting holes of 60 x 60 x 60cm.

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)

Transplanting in the field

·         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. 

Wind break

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

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.

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.

Intercropping

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

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.

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 pawpaw in the same field.

Birds- They feed on the ripe fruit.

Control

Harvest when the fruits are physiological mature)

Major Diseases

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

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) - 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

Control

Immersing fruits in warm water at 400 C for 20 minutes can control the fungi infection).

Rhizopus- It is a common postharvest disease of the pawpaws and is important only during storage and transit (sanitation in and around the packing area).

*Integrated pest Management is the recommended method for control of pests and diseases that includes good cultural practices, biological and chemical control.

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.

·         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 handling

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.

Challenges in production

·         The major problem faced in papaya production is significant post-harvest losses along the marketing chain. Factors such as fungal diseases, physiological disorders, mechanical damage, or a combination of these are the leading causes of post-harvest losse

·         Lack of quality planting material/seed is a serious draw back in production Most often farmers plant poor quality pawpaw of low market value and in some cases diseased material is used hence reducing economic lifespan of the orchard.

Advice to potential growers

·         Papaya production is expected to grow based on increased domestic consumption of the fruit throughout the year and high markets prices. There is also opportunity to utilize the fruits in value addition. Pawpaws can be intercropped with other crops thus providing extra income. Quality fruits can be obtained by ensuring the recommended pre-harvest and post harvest practices are adhered to.