Papaya is a popular fruit famous for its high nutritive and medicinal values. It comes early in bearing than any other fruit crop, produces fruits in less than a year and the production of fruits is quite high per unit area. Papaya is cultivated more or less on a commercial scale in the foothills and plain valleys of all states of the north eastern region. As per statistics available 3,670 hectares yield 47,280 tonnes of papaya annually. It is the fourth important crop of this region. Among the hill states, Mizoram has the largest area under this crop, followed by Tripura and Manipur, While in production Manipur contributes the maximum, followed by Tripura and Mizoram. Papaya is a native crop of Mexico, and was introduced in India in the 16th century. Now it has become popular all over India and is the fifth most commercially important fruit of the country.
Composition & Uses
Ripe papaya is one of the best refreshing fruits, rich in vitamin A and a good source of Vitamin B and Vitamin C. It supplies appreciable amounts of minerals, consisting mainly of iron, calcium and phosphorous and also a little protein. Papaya is rich in the enzyme papain, which helps in digestion of proteins.
The papain content of the fruit gradually decreases as it ripens. Due to papain content of raw papaya, it reduces the time of cooking of meat as well as makes meat very tender when cooked with a small piece of raw papaya. Ripened fruits are also used in preservation industries as raw material in preparation of mixed jam, jelly, marmalade etc. It is also used in the manufacture of a powder rich in minerals, proteins, fats, pectin and carbohydrates. The powder is used in a number of foods after artificial drying to reduce the moisture content to 6 percent. The green or unripe fruit is used as a vegetable and it can also be made into pickles. Ripe papaya and its seeds seem to have medicinal properties and are used in several disorders of liver, spleen and the digestive tract. Papain is commercially a very useful product. It is known to remove skin blemishes, and is considered beneficial for treatment of stomach ulcers, diphtheria and even cancer. It is also used in clarification of beer, in tanning industry and in manufacture of chewing gum. Thus papain extraction also gives an extra income to papaya growers.
Papaya is basically a tropical plant. However, it also grows well in sub-tropical parts. Those foot hills which enjoy a mild winter are ideal for papaya cultivation. Low temperature and frost limit its cultivation in higher altitudes. Excessively cold nights cause the fruits to mature slowly and to be of poor quality in winter season. It can be grown from the sea level to an altitude of 1000 metres, but above an altitude of 600 metres, size and quality of fruits gradually decreases. As it grows in sub-tropical and tropical climates, it can be cultivated in a temperature range of 25-35˚C. In this region it can be grown successfully as a rainfed crop in areas with 1500-2000 mm of evenly distributed annual rainfall, though yield may be poor when compared to an irrigated crop, because winter drought restricts development of the plants and the fruits. High humidity affects the sweetness of the fruits. Fruits tend to lose their sweetness in low temperature also. A warm and dry climate is needed during ripening season. It can not withstand strong winds being a tender and shallow-rooted plant.
Papaya can grow in many types of soils, except sandy and sticky or heavy clay soils. Papaya roots are very sensitive to water logging or standing water. Even forty eight hour submergence can be fatal for the plant. In heavy soils, water accumulates during high rainfall, and diseases like foot-root and root-rot occur, which may cause the plantation to be wiped out in a short time. Hence a slightly sloppy land is preferred to a perfectly leveled one. Hilly soil of this region is best suited, being well drained in organic matter.
Papaya is invariably propagated by seed. For propagation, seeds are collected from ripe, large sized, healthy fruits, essentially from female plants free from pests and diseases. Sometimes, the seeds fail to germinate because seed viability is completely lost in about 45 days. The removal of a mucilaginous covering (sarcotesta) from the seed is helpful in more rapid and uniform germination than those seeds with their sarcotesta intact. Removal of sarcotesta is easily done by fermenting the seed in a bucket of water for two to three days. The sarcotesta breaks easily when the fermented seeds are mixed with wood ash and are rubbed gently in a piece of gunny cloth. The seeds are washed to remove exogenous material by putting them in another pot or vessel containing water. The viable seeds sink in water, while the nonviable ones, sarcotestas and other debris float and can be skimmed off. The seeds can be sown immediately, or they can be stored after drying in shade in airtight containers. The seeds, however, should never be dried in sun, as this leads to a total loss of their viability.
Nursery sowing should be done 2 to 2½ months prior to the scheduled date of transplanting in the field. Middle of February to middle of March is the best time for sowing the seeds in north eastern hill region, for transplanting in the beginning of monsoon. It is better to sow the seeds in perforated polythene bags, 22 cm x 15 cm, and 150 gauge thick. In case of heavy and medium soils, bags should be filled with a 1:1:1 mixture of FYM soil and sand. A potting mixture of one part soil and one part FYM is ideal for north eastern region, having a porous soil. Seeds should be treated with 1 percent agrosan G.N. as prevention against damping off disease. Two to three freshly extracted or stored seeds are sown in each bag at a depth of 1.5 cm. Light watering, with a watering can, should be done every evening except on rainy days. The seeds germinate within 2 to 3 weeks. Only one healthy seedling is retained per bag in case of Coorg honey dew and solo variety. About 250-300 g of seeds is enough to raise a sufficient number of seedlings for planting an area of one hectare. Top dressing of seedlings in bags containing urea or ammonium sulphate should be avoided, as this encourages damping off disease and development of tall and lanky seedlings which are less suitable for transplantation. The main objective of rearing the seedlings in a nursery is to obtain healthy (15 to 20 cm tall at transplanting stage) and stocky seedlings with a large number of fibrous roots and leaves. This is best achieved by using good quality farm manure for making potting mixture. Spraying of papaya seedlings with GA at 50 ppm, alar at 250 ppm and phosfon-D at 250 ppm increases the number of female flowers. Nowadays attempts are being made to propagate papaya by tissue culture from stem segments, roots, and leaf segments.
Pits 50 cm in size are dug at a spacing of 2 to 2.5 metres during the first part of May. The pits are exposed to sun for a fortnight and filled with top soil along with 20-25 kg of farm yard manure, 1 to 1.5 kg wood ash and 1 kg bone meal in the form of mounds. In absence of rainfall, water is added to the pots to settle down the mixture properly. Before transplantation, pits re drenched with eldrin to avoid termite attack. When the seedlings are 15 to 20 cm tall, the bag is cut open with a razor blade and the seedlings are transplanted in the pits in the evening.Usually three seedlings are transplanted about 15 cm apart in each pit. Watering is essential after transplantation for a quick recovery from the transplanting shock.
A five month period from transplanting to first flowering is important for nutrition of papaya plants. The stem girth attained by a plant just before flowering decides the vigour and productivity of a plant. If the plant remains weak during this period owing to insufficient nutrition, production during the rest of its life is adversely affected. Therefore, fertilizers should be applied at frequent intervals and at proper rates for building a stout and vigorous plant before flowering, and to maintain its subsequent growth and productivity.
The importance of nitrogen, phosphorous and potassium for good growth and yield in papaya has been realized. A fertilizer dose of 400g nitrogen, 250g phosphorous and 400g of potassium per plant per year should be applied in six split applications under irrigated conditions, although in rainfed conditions, it can be given in two split doses; the first in the beginning of monsoon and second in the later part. If rainfall is well distributed from March to November, then it can be given in three split doses. Each plant should also be given 20-25 kg of farm yard manure once every year. At the time of fertilization, a sufficient amount of moisture is essential in the soil. The fertilizers should be well mixed in irrigation rings or basins by light digging or hoeing. Application of fertilizers should be stopped 6 months before harvesting the crop.
The papaya plant grows very quickly and comes to fruit in a year’s time, so intercrops are not usually taken in papaya plantations. Papaya itself is commonly used as an intercrop in tree fruit orchards. Papaya is a shallow-rooted plant, which should never be given deep tillage. Only removal of weeds is required whenever desired. Papaya requires a constant supply of moisture for continuous growth and production, but it is not possible in the hills of this region. However, when there is a danger of frost injury, supply of moisture is useful.
The male plants of papaya are generally vigorous in growth and start flowering after three months of transplanting. As soon as their presence is detected, most of them should be removed. However, for effective pollination of female flowers, about one male tree is maintained for every 10 female trees. Papaya starts flowering about five to six months after it is transplanted. Fruit setting commences a fortnight after flowering. When the fruits become about 3cm long, the smaller fruits should be thinned out to avoid over crowding. Fruit thinning is preferably done at regular fortnightly intervals. Due to adverse climatic conditions, flowers or fruits sometimes start dropping from the plant. To prevent fruit drop and to increase fruit size, spraying of Planofix (1 ml in 1 litre of water) during flowering and on tender fruits is beneficial. This much of the solution is sufficient to treat 10 fruits. Fruits take about four to five months to reach full maturity. Fruits which ripen on the trees are of the best quality and are suitable for table purpose as well as for local market. But for distant markets, they are harvested when they are firm, and only the apical end has started turning yellow. If planting is done in May, harvesting of ripened fruits can be achieved in the next April. Papaya fruits can also be artificially ripened well by treatment with one part of ethylene gas in 5000 parts of air in a closed chamber. Over-ripening of fruits on trees should be avoided as it may otherwise be easily damaged by birds. Yield per tree in a commercial plantation varies from 30 to 50 fruits per tree with an average weight varying from 20 to 35kg per tree in this region. In this region papaya plants have been found to bear fruits for 6-8 years. However in commercial productions it can be allowed to bear only for 3-4 years.
Diseases and pests
Papaya has no serious insect, pests, but it has some serious diseases.
Collar-rot or Foot-rot
It is caused by a soil borne fungus Pythium aphanidermatum. In this region, the disease occurs at the base of the stems particularly during the rainy season. The fungus attacks the bark and causes swelling, cracking and rotting of stems and roots, especially in waterlogged conditions or in extremely moist, sticky soils. The terminal leaves drop, wilt, turn yellow and fall.
Control measures: It can be checked by spraying/drenching 6:6:50 Bordeaux mixture or (0.2%) esso fungicide thrice during season. It can be avoided if the plants are on a well drained land.
It is caused by the fungus Rhizoctonia solani and Fusarium sp. in the nursery. In the later stages, this disease is caused by Phytophthora palmivora, mainly in the root system.
Control measures: Application of 100g of lime and 100g of copper sulphate in the pits is an effective preventive measure against this disease. Drenching with formaldehyde two weeks before sowing can give effective control in the nursery.
Damping off (Phytophthora sp)
This fungus kills young seedlings in the nursery stage. This can be prevented by sterilization of the soil of nursery beds with formaldehyde, two weeks before sowing, or treating the seeds with agrosan G.N., captan or Ceresan.
Leaf-curl and mosaic (Papaya ring spot or papaya mosaic virus)
They are observed during rainy season when the vectors are most active and cause considerable damage. In leaf curl, leaves of the plants become crinkled and curled, the plants get stunted with small leaf size and do not grow further.
The mosaic disease starts as necrotic dots on the leaves. The lamina becomes yellowish green, malformed, upright and with blistered patches on it. Fruits are also affected.
Control measures: Practically there is no control measure for these viruses. The virus affected plants should be quickly destroyed to prevent the spread of these diseases. To check the insect vector, plants should be sprayed with 0.05 percent Malathion or metasystox at 10-12 days intervals.
Root knot nematode (Meloidogyne incognita)
Affected plant shows withering, yellowing and wilting. Knot like structures appear on the roots particularly under water logged conditions.
Control measures:This can be checked by use of nematicides (nemagan, nemphas, etc) in the field.
The insect pests of papaya are not that harmful. The most important is the red spider mite, which occurs on the underside of the leaf, which they damage. It can be controlled by spraying fine lime sulphur. Birds cause considerable damage to papaya. Bird-scaring is an important item of expenditure in commercial plantations.