Introduction

Papaya (Carica papaya) is a perennial fruit tree widely cultivated in tropical and subtropical climates for its nutritive and medicinal values. It is very popular in Kenya where it is grown for both local and export markets.

Credit: greenlife.co.ke

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.

PawPaw Varieties in Kenya

The following are the common pawpaw varieties grown in Kenya;

  1. Solo produces small round sweet fruits with uniform sizes and shape. It’s hermaphroditic and popular for both local and export markets.
  2. Vega F1 produces medium sized fruits with an attractive red flesh. Fruits are firm and sweet, weighing 1-1.2kg.
  3. Sunrise produces smooth pear shaped fruits of high quality, weighing about 400-650g. Flesh of fruits is reddish orange and the variety is high yielding.
  4. Mountain produces small fruits only suitable for preserves and jam.
  5. Red royale F1 this is an improved breed that gives good quality fruits weighing 1.7-2.3kgs which have red attractive colour and are very sweet.
  6. Sinta F1 female fruits are round while hermaphrodite fruits are oblong with an average weight of 2kg. Flesh is deep yellow, firm and sweet.

Types of Papaya Plants

The types are based on the flowers arranged and can only be differentiated after the plants have flowered.

  • The male (staminate) – this has male parts and doesn’t produce fruits. Flowers are produced in large numbers in long dropping branches.
  • The female (pistillate) – has female parts only. Flowers are large, situated singly or in clusters near the tree trunk and close to the base of leaf stalk. It is pollinated through cross pollination and produces fruits that are sweetest in all the varieties.
  • The hermaphrodite- contains both male and female parts on the same plant thus capable of self-pollination.

Pollination is a key component in pawpaw production because it determines fruit set and quality.

Ecological Requirements

  • Rainfall– papaya cannot withstand prolonged drought. An even distributed annual rainfall of above 1000mm is suitable. Irrigation should be done in low rainfall regions.
  • Soils– the crop does well in light, well drained soils with PH 6-6.5 and rich in nutrients. Roots are very sensitive to waterlogging.
  • Temperature– papaya thrives in warm to hot regions of temperature range of 20-35 degrees centigrade. Fruit is sweeter when grown during warm sunny season.
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In good climatic conditions, fruits grow all year round.

Field Operations

Propagation

This is done majorly through two ways;

  • By seeds
  • Vegetative i.e. by tissue culture

Growing papaya from seeds is the easiest, cheap and most successful method.  Plants raised from seeds produce fruits of varied shapes, sizes, taste, colour, etc.

Vegetative propagation of pawpaw using tissue culture can result into superior plants with certain traits, e.g., resistant to pathogen attack, production of high yields etc. However, this method is rarely used because it is expensive.

Raising Seedlings

Seeds can be sown directly in the field or first raised in nursery beds, in polythene bags, containers etc.

  • Prepare a seedbed to a fine tilth.
  • Drench soil with a mixture of PYRAMID 700WP 100g+LOYALTY 700WDG 10g+ OPTIMIZER 20ml in 20litres of water. This eradicates soil diseases and pests, breaks seed dormancy, encourages uniform germination and supplies nutrients to the young plants.
  • Select seeds from a controlled pollination and dry them. The outer layer of the seed coat can be removed.
  • Soak seeds in OPTIMIZER 20ml/1l for 30-60minutes to break seed dormancy.
  • Place 4-5 seeds in holes, 1cm deep and 15cm apart and cover with a slight layer of soil.

Seeds germinate after 2-3weeks.

Transplanting

Seedlings are transplanted 4-5 weeks after sowing when they have attained 3-4 leaves or 15-20cm height. While transplanting, careful handling is important in order to avoid disturbing the roots.

Plants grown in a seed bed should first be hardened off.

In order to prevent transplanting shock, seedlings should be sprayed with OPTIMIZER 10ml/20l.

  • Prepare planting holes 60cm*60cm, 3 meters apart.
  • Mix top soil with manure and DAP and fill the holes with the mixture. To improve on nutrient uptake, root development, stimulate plant growth among other benefits, mix manure (1 ton) or fertilizer (50kg) with HUMIPOWER 1kg.
  • Plant 3-4 seedlings per hole for varieties with male and female flowers on different plants. Seedlings should be placed at the same depth as they were growing previously.

Newly transplanted seedlings should be watered regularly until they are established.

Cultural practices

Weeding

Weeds are plants growing in undesired places. They compete with the target crop for growth factors like nutrients, sunlight, space and water, as well as harboring pathogens which directly affects performance of the crop.

Spray CLAMPDOWN 480SL 150-300/20l, which is a non-selective herbicide used to control both broadleaved and grass weeds keeping the garden weed-free.

Irrigation

This should be done especially if rainfall is inadequate in order to ensure a steady supply of moisture and especially during flowering and fruiting stages.

Mulching

This helps in suppression of weeds and moisture conservation. Decomposed mulch materials release nutrients into the soil which are absorbed by the plants.

Pests and Disease Management

Pests

Fruit fly

The adults deposit their eggs under the skin of mature and ripening fruit. Some fruit flies lay eggs on green pawpaw, but most of the eggs die due to the latex secreted when fruits are punctured by females while laying eggs. The eggs hatch into maggots which feed on the flesh of the fruit causing it to rot. This may cause fruit fall.

Spray PENTAGON 50EC 10ml/20l or LEXUS 247SC 8ml/20l or PRESENTO 200SP 5g/20l

Red spider mites

They suck plant sap and this affects the general performance of the plant, e.g., poor plant growth, leaf drop, production of fruits with blemishes, etc.

Severe infestations occur during prolonged dry spells.

Spray ALONZE 50EC 5ml/20l or BAZOOKA 18EC 10ml/20l

Mealy bugs

They suck sap from tender leaves, petioles and fruits. Severely attacked leaves and fruits drop. They also excrete honey dew on which sooty mold develops.

Spray KINGCODE ELITE 50EC 10ml/20l or PRESENTO 200SP 5g/20l or LOYALTY 700WDG 5g/20l

Thrips

These are sap-sucking insects which attack and puncture shoots, leaves and flower buds as they feed. Severe infestation can cause flower abortion.

Spray ALONZE 50EC 5ml/20l or KINGCODE ELITE 50EC 10ml/20l or DEFENDER 25EC 40ml/20l

Whiteflies

These are white sap-sucking pests whose infestation causes curling and distortion of leaves and an eventually drop.

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They are also vectors of viral infections.

Spray TAURUS 500SP 10g/20l or LEXUS 247SC 8ml/20l or KINGCODE ELITE 50EC 10ml/20l

Scales

They cause damage by feeding on shoots, leaves and fruits.

As they feed, they release honey dew which facilitates the development of sooty mold.

Spray LOYALTY 700WDG 5g/20l or EMERALD 200SL 10ml/20l or PRESENTO 200SP 5g/20l

Nematodes

These are small, microscopic wormlike parasites which feed on the plant roots resulting into formation of galls/swellings.

Infestation may cause the plant to topple over due to declined vigour.

Drench soil with ALONZE 50EC 10ml/20l or always mix basal fertilizer (50kg) with ADVENTURE 0.5GR 2kg.

Birds

They feed mostly on the ripe fruits.

To prevent this, harvest fruits immediately they attain physiological maturity.

Diseases

Damping off

This is a soil borne infection which causes rotting of roots and stems leading to yellowing, leaf and fruit fall and subsequent death and toppling of the plant.

Drench soil with PYRAMID 700WP 100g/20l or CHANCETYL ELITE 800WDG 100g/20l or MILLIONAIRE 690WDG 100g/20l

Papaya Ring Spot

This is a viral infection majorly spread by aphids or be mechanically transmitted. Infection causes mottling of leaves and vein clearing. In severe cases, the lobes of the leaves become distorted reducing the life size.

On the fruit, dark circles/rings are seen which remain green when the fruit ripens. Severely infected plants do not flower and die young.

Control aphids by spraying KINGCODE ELITE 50EC 10ml/20l or PENTAGON 50EC 10ml/20l or PRESENTO 200SP 5g/20l

Powdery mildew

Plant parts are covered with whitish fungal growth.

Infection causes distortion of leaves and shoots. As the fruit develops, the white powder disappears leaving it grey-scared.

Premature fruit fall may occur.

Spray RANSOM 600WP 15g/20l or DUCASSE 250EC 20ml/20l or EXEMPO CURVE 250SC 15ml/20l

Anthracnose

Infection is characterized by brown to black sunken lesions on the plant parts. Infected fruits rot.

Spray RANSOM 600WP 15g/20l or DUCASSE 250EC 20ml/20l or ABSOLUTE 375SC 10ml/20l

Bunchy top disease

This is a viral infection spread by leafhoppers whose symptoms include oil streaks on stem, yellowing of upper leaves, bunching and stunting of top leaves and death of plant top.

Control vectors (leafhoppers) with PRESENTO 200SP 5g/20l or KINGCODE ELITE 50EC 10ml/20l or LEXUS 247SC 10ml/20l

Leaf spot

Symptoms starts as small yellow spots which expand. In severe cases, the leaf drops. This greatly affects the performance of the plant.

Spray RANSOM 600WP 15g/20l or DOMAIN 250EC 10ml/20l or EXEMPO CURVE 250SC 15ml/20l

Papaya mosaic

This is a viral disease spread by aphids, which is more serious on young plants. Leaves show symptoms of reduced size, patches of dark-green tissue alternating with yellow-green.

Infected plants have reduced growth and fruits develop water soaked lesions with central solid spots.

Control aphids by spraying KINGCODE ELITE 50EC 10ml/20l or PENTAGON 50EC 10ml/20l or LEXUS 247SC 8ml/20l

Leaf curl

This infection is transmitted by whiteflies and causes curling, crinkling, vein clearing& thickening and deformation of leaves. Defoliation occurs in severe cases.

Control whiteflies with TAURUS 500SP 10g/20l or LEXUS 247SC 8ml/20l or KINGCODE ELITE 50EC 10ml/20l

Phytophthora stem & fruit rot

Infection is characterized by water soaked lesions on unripe fruits and stems. Mature fruits are covered by white fungal growth.

Spray MILLIONAIRE 690WDG 40g/20l or FORTRESS GOLD 720WP 40g/20l or EXEMPO CURVE 250SC 15ml/20l

Nutrition & Nutritional Deficiencies

Papaya nutrition is key for a year long high and quality fruit production.

Both basal and foliar fertilizers should be applied in order to ensure that the plants are supplied with both macro and micronutrient elements..

Basal fertilizers are absorbed by the plants through the roots and include DAP, CAN, NPK, UREA, among others. Farmyard manure could also be added, depending on the organic matter of the soil.

Foliar fertilizers are absorbed by the plants through the foliage and include OPTIMIZER, DIMIPHITE, ZINC GOLD, LAVENDER, GATIT SERIES, VITABOR GOLD, among others.

Sufficient nutrient supply prevent deficiencies which weaken the plants making them susceptible to attack by pathogens.

Deficiencies

Phosphorous deficiency

Deficiency stops plant elongation and leaves become irregularly necrotic with a characteristic blue or dark green colour. Production is greatly reduced.

Correction; spray DIMIPHITE 30ml/20l or LAVENDER 20ml/20l or GATIT SUPER START 50g/20l or PLANT SOUL 20ml/20l

Potassium deficiency

Leaf size reduces, with its margin being necrotic and fruit shape is distorted. In severe cases, fruits and leaves drop.

Correction; spray DIMIPHITE 30ml/20l or GATIT SUPER FLOWERS & FRUITS 50g/20l or LEGENDARY40ml/20l

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Nitrogen deficiency

Leaf petioles become thin, short and compressed.  Stunted growth is noted with leaves becoming pale and reduced. These lead to decreased yields.

Correction; spray LAVENDER 20ml/20l or GATIT SUPER GROWTH 50g/20l or

Boron deficiency

Deficiency first appears in shoot apical meristems and in fruits, majorly causing deformation. Mature plants are dwarfed and fruit set is greatly reduced.

In severe cases, surface of fruits is covered with lumps.

Correction; spray VITABOR GOLD 20ml/20l

Zinc deficiency

Deficiency causes interveinal yellowing and malformation of leaves, rosetting of leaves thus reducing photosynthetic area. Young plants may die off.

Correction; Spray ZINC GOLD 10ml/20l

Maturity, Harvesting & Post-Harvest Handling of Papaya

Papaya plants start flowering 5-8 months after planting and fruits are ready for harvesting approximately 2 months after flowering stage. Maturity however depends on the variety. Harvesting is done by cutting off the fruit from the tree.

Note that fruits do not mature at the same time and thus only the mature ones should be harvested.

It is recommended that fruits be harvested just before ripening.

Fruits should be handled carefully to avoid bruises which could create avenues for entry of storage pathogens.

The harvested fruits should be washed in order to remove any substances which could affect its shelf life.

Bruised or fruits with any damages should not be stored together with the good ones.

Ripe fruits are rich in vitamins and other nutritive elements and are commonly used for desserts or processed into other products.

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 the first 3 to 4 years. It is therefore advisable to renew the plantation every 4 years.

Challenges in production

  • The major problem faced in papaya production in Kenya 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.

NOTE

  • Whenever doing foliar sprays, always mix the product(s) with INTEGRA 3ml/20l. This is a sticker, spreader and penetrant which helps in improving the products’ efficacy, giving more effective results.
  • JAMBO CLEAN 100ml/20l is used to clean sooty mold which results after infestation with sap-sucking pests like mealybugs.
  • CADILLAC 800WP is a preventive fungicide which should be used before a fungal infection has begun on the plant.
  • OPTIMIZER 10ml/20l is a superior foliar fertilizer which helps in management of plant stress during adverse climatic conditions, plant immune build up, prevention of flower abortion, improvement of fruit quality & quantity among other benefits. It provides both macro and micronutrients and growth hormones to the plants.
  • Alternation of various chemicals (especially fungicides and insecticides) throughout a crop’s season help in preventing resistance build-up by the pest, which could happen if only a single chemical was used.
  • All basal fertilizers and manures should be mixed with HUMIPOWER, which adds organic matter into the soil, improves nutrient uptake, stimulates beneficial microbial activities, promotes electrochemical balance and stimulates plant’s development among other benefits.
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