MANGO GROWTH AND EXPORTS
By Dr. S.M. ALAM
June 28 - July 04, 2004
There are numerous types of mango varieties around the world, many experts believe that mango (Mangifra indica L.) is actually native to Africa, some parts of southern Asia, especially Myanmar and eastern India , Pakistan and Latin America. It spread early on to Malaya, eastern Asia and eastern Africa. It is from these countries that the fruit started its global journey. From Latin America, mango found its way up north to Caribbean then Central America and in the late 1880s, it made to California, today the capital of mango farming in North America.
Most of the blended and improvised mango varieties grown in Pakistan originated in the south of India. Today, there are over 250 varieties that are grown here. Of these, the most famous include Sindhri, Anwar Rator, Alphanso, Bombay Alphanso, Dasehri, Saharni, Langra, Chausan etc. These main varieties then have further sub-varieties. For example, one of the most popular mango varieties , the Sindhri, reportedly has over two dozen sub-varieties. All mango varieties in Pakistan are hugely popular. However, the Sindhri and Anwar Rator are perhaps the most popular. Different varieties of mango are consumed in different ways. For example, more fleshly varieties are supposed to be chopped into cubes or slices to be consumed, whereas some others specially reserved for juice.
The Indian race is intolerant of humidity, has flushes of bright red new growth that are subject to mildew, and bears monoembryonic fruit of high color and regular form. The Philippine race tolerates excess moisture, has pale green or red new growth and resists mildew. Its polyembryonic fruit is pale green and elongated kidney-shaped.
Primary mango growing areas of Pakistan include the northren belt of Sindh and southern parts of Punjab. Mirpurkhas in Sindh and Multan in Punjab are prominent mango sectors of the country. The two areas have a hot and long summer, hence, they are naturally better suited for growing mangoes. The reason is that mangoes need extremely high temperatures to ripen just before the picking season and the searing heat of the said region makes for great juicy fruit. The mango belt of Pakistan grows some of the finest varieties of the fruit in the world.
Mango is a water-intensive fruit tree, requiring a lot of water to grow in the hot summer months preceding the monsoon. Pakistan has been a great producer of the fruit. It produces over 10 million tons of fresh mango annually. But only a fraction of that, however, reaches to international markets. Many believe that the recent government initiative like holding retail floor shows abroad and infrastructure developments like the building of the cold storage facilities for perishable storage at the country's airports, will go a long way in helping to establish Pakistan as a mango exporter. However, there is also the realisation that much still needs to be done on the front of particularly packing, branding and quality control.
Mango tree basically require a frost-free climate. Flowers and small fruit can be killed if temperatures drop below 40°F, even for a short period. Young trees may be seriously damaged if the temperature drops below 30°F, but mature trees may withstand very short periods of temperatures as low as 25°F. The mango must have warm, dry weather to set fruit. Mangoes luxuriate in summer heat and resent cool summer fog. Wet, humid weather favors anthracnose and poor fruit set. Dwarf cultivars are suitable for culture in large containers or in a greenhouse. Mango trees make handsome landscape specimens and shade trees. They are erect and fast growing with sufficient heat, and the canopy can be broad and rounded, or more upright, with a relatively slender crown. The tree is long-lived with some specimens known to be over 300 years old and still fruiting. In deep soil the taproot descends to a depth of 20 ft, and the profuse, wide-spreading feeder roots also send down many anchor roots which penetrate for several feet.
The leaves are dark green above and pale below, usually red while young. The midrib is pale and conspicuous and the many horizontal veins distinct. Full-grown leaves may be 4 to 12-1/2 inch long and 3/4 to 2 inch wide, and are generally borne in clusters separated by a length of naked stem bearing no buds. These naked stems mark successive flushes of growth. Each flush of growth will harden off to a rich green color before the next flush of growth begins. The yellowish or reddish flowers are borne in inflorescences which appear at branch terminals, in dense panicles of up to 2000 minute flowers. These flowers respire a volatile substance, causing allergic and respiratory problems for some persons. Pollinators are flies, hoverflies, rarely bees. Few of the flowers in each inflorescence are perfect, so most do not produce pollen and are incapable of producing fruit. Pollen cannot be shed in high humidity or rain. Fertilization is also ineffective when night temperatures are below 55°F. Mangoes are monoecious and self-fertile, so a single tree will produce fruit without cross pollination. Polyembryonic types may not require pollination at all. Branches may be ringed to induce flowering, but the results are mixed.
The fruits grow at the end of a long, string like stem (the former panicle), with sometimes two or more fruits to a stem. The fruits are 2 to 9 inches long and may be kidney shaped, ovate or (rarely) round. They range in size from 8 ounces to around 24 ounces. The flower scar at the apex is prominent, in some cultivars bulging from the fruit. The leathery skin is waxy and smooth, and when ripe entirely pale green or yellow marked with red, according to cultivar. It is inedible and contains a sap that is irritating to some people. The quality of the fruit is based on the scarcity of fiber and minimal turpentine taste.
The flesh of a mango is peach like and juicy, with more or less numerous fibers radiating from the husk of the single large kidney-shaped seed. Fibers are more pronounced in fruits grown with hard water and chemical fertilizers. The flavor is pleasant and rich and high in sugars and acid. The seed may either have a single embryo, producing one seedling, or polyembryonic, producing several seedlings that are identical but not always true to the parent type. It is impossible to distinguish true-to-type from zygotic seedlings from the same fruit. Some seedlings produce numerous tiny, parthenocarpic fruits which fail to develop and abort. Mango trees tend to be alternate bearing.
The mango grows to a good size and casts a dense shade, but the roots are not destructive. It requires full sun and perfect air drainage in winter. It does best at the top or middle level of a slope. A windbreak should be provided in exposed areas. The trees may also need staking. In the desert it needs the shade of other trees; or plant on the north side of the house. In the garden or near the coast, plant against a south wall, or in an area surrounded by paving, to provide maximum heat. In the greenhouse, full light and free air movement are important to avoid disease.
Mangoes will grow in almost any well-drained soil whether sandy, loam or clay, but avoid heavy, wet soils. A pH between 5.5 and 7.5 is preferred. They are somewhat tolerant of alkalinity. For good growth, mangos needs a deep soil to accommodate their extensive root systems. Irrigation should start when the weather warms: February in the desert, April at the coast. Continue every one to two weeks, more often in light soils, nearly continuously in the desert, until the fruit is harvested. Irrigation may be discontinued when rains are sufficient to maintain soil moisture. In the greenhouse keep watered until the fruit is harvested, then reduce to the minimum required to avoid wilting. Watering is then increased after one to two months to initiate a new bloom and growth cycle.
Mango trees require regular applications of nitrogen fertilizer to promote healthy growth flushes and flower production. Chelated micronutrients, especially iron, are also often necessary. A feeding program similar to one used for citrus is satisfactory, but do not fertilize after midsummer. Organic fertilizers perform best, since the trees are subject to fertilizer burn. Young trees are particularly sensitive to over-fertilizing, but respond well to fish emulsion. Sandy soils require more fertilizer than loam or clay. Healthy trees require little pruning, although pruning to stimulate new growth promotes uniform annual bearing. Removing some flower clusters during a heavy bloom year may also alleviate alternate bearing. Mangoes may be pruned to control size in late winter or early spring without a loss of fruit. Sap and debris can cause severe dermatitis, similar to poison oak. It is best to avoid burning pruning or litter.
During the first two years, the trees should be given some protection such as an overhead cover during any frost threat. Once the tree is 3 to 4 feet high, overhead protection is difficult but still worthwhile, especially if an unusual cold snap is predicted. Frost damage can also be avoided by erecting an overhead lath shelter, orchard heating, placing lights under the canopy, or using foam or straw trunk wraps. Do not prune dead parts until all frost danger is past. To grow mangoes from seed, remove the husk and plant the seed (before it dries out) with the hump at soil level. The seeds normally germinate in two to four weeks, and do best with bottom heat. Multiple polyembryonic seedlings should be carefully separated as soon as they have sprouted so not to loose the cotyledons. Seedling mangoes will bloom and bear in three to six years. Some success at grafting can be obtained in April and September, but better luck is more likely during May through August. Small plants with a diameter of a pencil graft well with the common whip graft. On larger trees the crown groove bark graft allows several scions to be put on at once. Fully grown trees may be topworked by crown or groove bark graft, or prune hard and whip graft sprouts later. Plastic bagging with a few drops of moisture improves the graft's chances of being successful. Graft in the second year, using cleft, side or tongue (splice) graft in midsummer. Scion and stock should be swelling for a new flush of growth. Grafts are most successful if the leaves are allowed to remain below the graft, but remove suckers. Use pencil-sized scions of hard wood with three or four nodes. Cover with loose punctured white paper bag for shade. If top working, then it is not necessary to dehorn the entire tree at one time; leave at least two fully leafed branches intact.
The mango is a suitable and productive tree for growing in a container or greenhouse. Start with established plants of named cultivars. Select the finest Indian cultivars, which are most rewarding for the effort involved. A large tub is required, with casters for easy moving. In the greenhouse, the atmosphere should be kept dry as possible to avoid anthracnose. Place a fan nearby to move the air around trees and use ventilators. The plants should be hosed down in the morning on a weekly basis to control mites. A regular spraying of appropriate pesticides for anthracnose and mealy bug may also be needed. The location of the intended planting will dictate the choice of cultivars.
Some pests such as Scale, mealy bugs and mites are frequent in the orchard. Thrips often turn leaves rusty brown. Malathion is the conventional spray for insect pests; sulfur works on mites. Gophers are attracted to the roots. The flower panicles, young fruit and leaves are subject to powdery mildew (Oidium mangiferae), especially in rainy weather or frequent fog. A spray of powdered kelp at bud break will often control it. Sodium bicarbonate and fungicide sprays are also effective. Trees planted in pavement openings seldom develop mildew. Bacterial spot (Colletotrichum oleosporides) distorts and turns developing leaves black and disfigures developing fruit. Infection may spread to fresh young growth. Anthracnose can be controlled with bimonthly applications of copper spray or captan as a growth flush begins, and until the flowers open. Resume spraying when the fruits begin to form. Mango trees are very sensitive to root loss that can occur from digging, transplanting or gopher damage. "Soft nose," a physical disorder of shriveling at the fruit apex, seems associated with excessive nitrogen in soil. Exposed fruits sunburn in high temperatures.
Mango fruit matures in 100 to 150 days after flowering. The fruit will have the best flavor if allowed to ripen on the tree, although winter-maturing fruits must be ripened indoors in coastal California. Ripening fruit turns the characteristic color of the variety and begins to soften to the touch, much like a peach. Commercial marketability requires 13% dissolved solids (sugars). When the first fruit shows color on tree, all of that size fruit or larger may be removed; repeat when remaining fruit colors. Do not store below 50°F. The fruit ripens best if placed stem end down in trays at room temperature and covered with a dampened cloth to avoid shriveling.