Introduction
Papaya, carica papaya, is one of the most important fruits of the tropics.Its important for its nutritive as well as medicinal value.Papaya is a herbaceous shrub and not a true tree thus its usually susceptible to toppling during high winds. Most commercial varieties flower 2.5 months after planting with fruit set after 3.5 months from transplanting.
Fruits maturity occurs 8.5 months from seeds after germination or 4 months from flower bud formation. In most cases the sex of the Flowers determine the shape, with female flowers producing rounded fruits while hermaphroditic flowers produce elongated pear shaped fruits.
Varieties
The major papaya varieties grown are; Honey dew, Kiru, Mountain Solo, Sunset and Waimando. Growing of this fruits has generally increased in hot areas of Machakos, Kitui, Makueni and Kajiado areas.
Seed production
Papaya is propagated by seed. To reproduce the desired characteristics it is best to get seeds through controlled pollination. The fleshy outer layer of the seed coat (sarcotesta) enveloping the seed is removed because it inhibits germination. Thoroughly dried seeds stored in air-tight containers remain viable for several years. Seeds are sown in small containers (tin cans, plastic bags or paper cups) at the rate of 3-4 seeds per container.
Sterilized soil minimizes losses resulting from nematodes and damping-off fungi. Germination takes 2-3 weeks. Seedlings are transplanted about 2 months after sowing. Treatment with fungicide and pesticide is necessary to avoid attack.
Environmental Requirements
Papaya prefers fertile soils with good drainage and PH of about 6.5 . They do not do well in heavy clays and saline soils. Papaya also doesn’t tolerate strong wind,flooding or prolonged droughts. Temperature requirement is between 21 -33 degrees.
Land preparation
Recommended spacing for papaya fruits varies with spacing of between 2-2.5m between plants and 2.5-3m between rows. This gives a plant density of 1000-3000 plants/hectare or 400-1200 plants/acre
Planting
During planting, cover the seedlings slightly with soils in holes after properly drenching the planting area to ensure disease and pest free planting. Ensure the plants are staggered along to meet ensure they capture adequate sunlight. Ensure during planting you don’t disturb the roots.plant on molds or ridges.
Propagation of papaya using tissue culture is fast gaining popularity, mainly because tissue culture has numerous advantages over other conventional methods of propagation. Tissue culture facilitates rapid production of disease free plants. In Kenya such plants are available from Kenya Agricultural Research Institute (KARI), Thika as well as several private companies
Nutrition
Papaya nutrition is key for a year long high and quality fruit production. Apply fertilizer around each plant ensuring you use chlorine free fertilizers since papaya is sensitive to chlorine. Apply high phosphoric fertilizer one week after transplanting.
Apply about 60g of high nitrogen fertilizer after every week to ensure proper foliage and vigor to ensure high yields. Apply potassium based fertilizer such as Goldchance Multi Super K or Lavender Fruit & Flower at flowering and fruit set.
Goldchance® Multi Super K is a highly soluble NPK Water Soluble Compound Fertilizer:Nitrogen(as N)=13.3%,Nitric Nitrogen(Water Soluble as N-NO3)=12.9%, Ammonium Nitrogen (as N-NH4)=0.4%,Water Soluble Phosphorous(as P2O5)=2.0%(P=0.9%),Water Soluble Potassium (as K2O)=44.2%(K=36.5%).
Papaya also requires trace elements particularly boron(Vitabor Gold) monthly to ensure good quality fruits, and rapid flower set. Calcium(Ferrari gold) is also among the required elements for quality,shelf live and texture. Calcium deficiency in papaya also leads to depressed fruit set .
Weed control
Weeds in papaya are predisposing to pests and diseases. Ensure the field is weed free thus reduce competition for nutrients. Herbicides such as Catapult are used as long as they don’t come into contact with the plant.
Irrigation
Water is important through especially at fruit set and development. Drip irrigation can be used during dry spells with a weekly requirement of about 23 liters/plant/week.
Common pests and Diseases
Diseases
Bunchy top virus-
This is a viral infection spread by leaf hoppers(Empoasca stevensii).symptoms include oil streaks on stem, yellowing of upper leaves, bunching and stunting of top leaves and death of plant top
Antracnose
– its a fungal infection caused by colletotrichum gloeosporioides. This infection starts as small round dark spots on ripening portion of fruit.as fruits ripen spots enlarge to form circular sunken areas. Absolute at a rate of 10g/20L controls this.
ABSOLUTE® 375SC is an enhanced excellent systemic fungicide with preventative and strong curative actions on a wide range of diseases in ornamentals, vegetables, fruits trees and cereals. It is absorbed by the plant and distributed quickly acropetal way.
Papaya ring spot virus
– its a viral infection in papaya spread by aphids, leaves roll upwards , affected leaves are light green with oily streaks on mature papaya . viruses are vectored by thrips and leaf hoppers hence controlling them with Lexus or Kingcode Elite® 50 EC helps reduce the viruses.
KINGCODE ELITE® 50 EC is a highly systemic and contact insecticide for foliar and stem application and is active particularly against sucking insects and chewing insects with broad spectrum long residual activity widely used in agriculture for controlling insect pests including aphids, thrips, whiteflies, diamond back moth, leaf miner, African bollworm, pod borer, stem borers and leaf beetle in a broad range of edible and ornamental crops.
Powdery mildew-
Characterized by whitish powder on the leaf surface. It reduces photosynthetic efficiency, and leads to yellowing and leaf fall.
Damping off and root rot-
This is a damaging fungal infection caused by pythium (pythium aphardematum). This leads to stem and root rot leading to yellowing, leaf and fruit fall and subsequent death and toppling. Proper sanitation and plant drenching procedures are key to ensure disease free production.
Pests
Papaya fruit Flies
Two species of fruit flies have been recorded from papaya in East Africa, namely Bactrocera invadens and Ceratitis rosa Fruit flies usually deposit their eggs in ripe 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. Developing larvae cause rotting of ripening fruits. Fruit flies are a major concern of papaya-importing countries.
 spider mites
Mites do not spare the papaya fruits. They attack the underside of plant leaves causing yellowing, discoloration thus compromising the Quality. Spider mites attack mostly during dry weather. Alonze 50 EC has proved to be a good control for spidermites.
Whiteflies
Whiteflies have become a modern threat for papaya farming. They Attack the leaves causing yellowing of leaves. The whiteflies also lead to honey dew formation /sooty mold which reduced the fruit quality, color and taste
Bugs-
various types of bugs attack the pawpaw plant. Bugs suck the plant sap causing the plants to turn yellow. They also make silvery marks and white deposits on the leaves and fruits reducing the quality. Mealybugs are the major threat in papaya production.
Harvesting
The stage of physiological development at the time of harvest determines the flavor and taste of the ripened fruit. The appearance of traces of yellow color on the fruit indicates that it is ready for harvesting. Fruits harvested early have longer post harvest life, but give abnormal taste and flavor. The fruits also tend to shrivel and suffer chilling injuries when refrigerated. The fruit is twisted until the stalk snaps off or cut with a sharp knife. 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 to 4 years. It is therefore advisable to renew the plantation every 4 years.
