MANGO PROFILE

Compiled by FTF Volunteer Juan Guzman for farmers in Guinea

The act of growing and selling mangos is no longer considered a simple activity. It involves many factors as well as the interaction of many other industries to make it possible. It involves labor, directly in the field and packing facilities and indirectly in transport-distribution. It involves supplies and services such as agricultural inputs, transportation, grading, packaging, banking, etc.

Botany: The mango, Manguifera indica, L., is a member of the cashew family the Anacardiaceae.

The sap of the mango can cause dermatitis, this is due to the presence of oxalic acid crystals. The tree is an evergreen and its growing habits depend on the variety, but it is an open growing tree. The growth of the tree occurs in cycles between March and September. This growth does not happen at once.

Flowers are on panicles that will develop from terminal buds. Floral bud differentiation happens after periods of stress or periods of dormancy, changes or drops of temperature during the cool season happen to stimulate this differentiation.

A normal panicle can be as long as 90 cm and have as many as 100 to 700 flowers. In the Northern Hemisphere, flower promulgation is from December to March, depending on the variety and climate. The flowers are stigmated or perfect, perfect flowers are present mostly at the end of the panicle. (Perfect flowers have both the male and female organs.)

The fruit in the Northern Hemisphere will generally mature from May to October. The seed that develops can contain either one embryo or two or more.

Pollination and fruit set: Mono-embryonic mangoes have the tendency to produce light crops. Mango flowers open about two hours after sunrise on sunny days and may last up to 4 hours. The stigmas are viable for 18 hours. The mango flowers can be insect-pollinated, but bees are not attracted to mangoes. The role of temperature in pollination and fruit set has not yet been defined. Some varieties set fruits better at lower temperatures.

Varieties: Around the world there are hundreds of mango cultivars. In Florida alone, there are more than one hundred, but Tommy Atkins, Keith, van Dyke, Glen, Kent and Haydn cover more than 80% of the commercial varieties.
 
To select a good mango for commercial use, Florida has used the following criteria:

1- bears regularly

2- high percentage of perfect flowers

3- fruit with attractive colors (red, orange, gold)

4- resistant to internal break down

5- long shelf-life, transport-tolerant (10 to 14 days after harvest)

6- resistant to anthracnose

7- rich in flavor, high sugar, low fibers

8- seeds no more than 10% of weight of fruit.

If these standards are applied seriously, one will see that not too many varieties fit the description. Also, those that fit the best (Tommy Atkins, for example, which has beautiful colors and is a great producer) do not satisfy the consumers (it does not possess much taste). Conversely, Haydn is very good eating quality but possesses poor transport and anthracnose resistance. Clearly tradeoffs must be considered in selecting the appropriate variety.

Varieties classification

It must be remembered that this seasonality classification is for the Northern Hemisphere, with the peak harvest periods occurring progressively earlier in the year as one approaches the Equator.

Propagation: Mangoes are propagated vegetatively and by seeds. The main use of seedlings is as rootstock for grafting. There is not much research on rootstock for mangoes, but poly-embryonic seeds have been used the most, especially the variety Turpentine, due to its vigor and prolific capacity. The seed is only viable for 2-3 weeks with rapid loss of germination vigor after that. The outer cover (husk) must be removed, seed planted with convex edge up and leaving a small portion of the seed out. Germination occurs in one or two weeks and the seedling is ready for grafting after a couple of months of growth and finally ready to be transplanted to the field the following year, just before the first rains.

Climatic requirements: Mango is a tropical plant, from relatively warm climates, but a mature tree can be subjected to low temperatures like 4 degrees Celsius for a few hours, with very little damage. Rainfall requirements are from 50mm to 250mm per year, though mangoes are capable of handling up to 2000mm/year.

Soil: Mango prefers deep, lose soil, but can produce well in shallow rocky soil if water and nutrients are supplied.

Nutrition: The mango tree extracts from the soil:

Nitrogen is needed for the tree's growth and yield; it is very easily lost to rain. Nitrogen should be applied depending on the size of the tree and its yield. An amount such as 450g of nitrogen can be applied for every 25kg of fruit on young bearing trees, reducing it as the tree grows older to 90g to 135g for every 25kg of fruit.

Phosphorus (P) is used in small quantities and does not leach away from soil as does nitrogen. It is used at a rate of about 25% of the quantity of nitrogen formula.

Potassium (K,0), after nitrogen, is the second-most important element in quantity terms. As for nitrogen, potassium can be washed out by rains and should be applied at the same rate as nitrogen.

Other elements used by mangoes but at a smaller scale are the so-called microelements. These are:

-- Magnesium (Mg). Even though it is classified as a microelement, it is used by the mango tree in great quantities. It should be added to the fertilizer at the rate of 20% of the potassium.

-- Manganese (Mn);

-- Copper (Cu); and

-- Zinc (Zn) are used by the tree and these three elements should be applied periodically in foliar formulas.

As a general rule, 4.5kg to 5.5kg of a formula 8-0-8-2 or 8-2-10-3 of N-P-K-Mg is recommended for young trees, reducing the percentage of nitrogen as the tree matures.

Fertilizer should be spread evenly, avoiding concentrations of salt near the trunk of the trees.

Soil pH should be 6-7. In acid soils, dolomite (calcium limestone) should be applied at the rate of 1000kg to 2000kg per hectare. "Soft nose", a physiological disorder in the flesh of the fruit, is cause by lack of calcium in the soil.

Soil and/or leaf analysis should be done to the plantation periodically to evaluate the presence of nutritional elements and to design fertilizer programs.

Cultivation: In bearing trees, little cultivation is required. Only keeping the weeds down by mowing and herbicide applications.

Pruning: Young trees require little pruning, following only some formation pruning or training. Low side shoots should be eliminated. Bearing trees are pruned when branches start to crowd each other. Also dead branches and sick ones should be removed. Larger cuts of about 6cm diameter and up should be covered with paint to prevent penetration of disease agents. Paints with asphalt base can be used.

Irrigation: New plantings will appreciate moisture around the root zone. A shallow basin around the trunks will help to keep water. A dry period at flowering will help the fruit setting, keeping anthracnose out of the bloom and after the fruit set. However, excessive drought will express itself in fruit drop, so during the fruiting period some water should be applied if rain is lacking.

Production and marketing: Seedlings take about 5 to 7 years on average to produce fruit. Grafted trees will go into production even the same year of grafting, but trees should be allowed to grow 2 to 3 years before leaving the fruits to develop so that the trees are allowed to grow and form a more robust canopy. Yields will vary from different varieties, but average production of 24 MT to 40 MT per ha can be expected in fully mature trees.

Fruit supply in the Northern Hemisphere can be expected from May to September. But this can be greatly affected by geographic position and climatic situation and as per market demands and pressures. Variations of as much 3 weeks can be expected from one season to another. The harvesting time depends on the variety and may change each year.

No specific standards have been set for mango harvesting with respect to either the maturity or the sugar content.

Traditionally, change in fruit shape and color have been considered signs of maturity, but once again this will vary from one variety to another and weather conditions and position of the fruit in the tree will affect color and shape. Fruit exposed to sun, for example, will have a different color than those inside the canopy.

A more reliable indicator of maturity is time after flowering. The time from flower to ripening takes from 15 to 20 weeks, therefore it is very important to know your flowering date in your plantation and in each one of your trees.

The best maturity test is the color of the flesh. One should cut some fruit from the grove and check for change of color inside, around the seed. This color change is a positive indication of maturity, and results from the transformation of starch into sugar.

Fruit should be picked at least once a week. This will make 5 to 7 harvests for any given tree, allowing a better quality of fruit to be transported to the market as well as harvesting more fruit, with fewer losses due to fruit drop.

Very good care should be taken in the handling of the fruit. Significant losses due to improper handling have been reported in Guinea.

Fruit that can be reached by hand from the ground should be picked by cutting the stem 6-10 cms from the fruit, leaving a portion of it attached to the fruit to avoid sap spill on the fruit skin. Fruit located high on the tree will require a ladder or a fruit-picking pole with a blade to cut the stem. A prototype was made and tested in Kankan and subsequently a number were manufactured; these are now available at a modest cost from FICA or they can be made in any basic workshop in Guinea.

The fruit should be picked in the coolest daylight hours and immediately placed in buckets or containers out of direct sunlight. The use of containers is important in avoiding large groupings of fruits to diminish the damage from one fruit's weight against the other.

The fruit should be transport immediately out of the sun and taken to a packing facility to be cooled off.

Packing: Once in the packing house, the fruit will have the stem cut, washed, graded and packed and immediately refrigerated to slow down the ripening process. The fruits' temperature should be lowered to 12.5 degrees Celsius and maintained at that temperature until it reaches the market. At the market, the temperature can be raised to 18.5ºC for ripening. Even for domestic marketing, the simple process of providing a cool-water wash after harvest should be employed even if downstream refrigeration is not being used. This will extend the life of the fruit somewhat and its appeal to buyers. The most common box is the 4.5kg box, with dimensions of 32cm x 37cm x 10cm. The number of fruit placed in each box will vary with the variety. The box should indicate the count of fruit, the weight, the variety, and the port of origin. It would also be good to indicate the date of packing.

Marketing: In the past few years, it has become more difficult to predict the mango's market for the following season due to the constant increment of the mango supply from all over the tropics. This forces the producers to pursue alternatives on delivery dates and value-added opportunities. Supplying markets in the off-season has been the biggest challenge as well as the greatest opportunity the market has presented to the growers. The average price in the United States market recently has been being in the US$4.50 per 4.5kg box.

Diseases: Mangoes are susceptible to a few problems, most of them affecting the fruit quality. Luckily, in the Kankan area, early mangoes (through June) almost completely escape disease and produce near perfect fruit.

Anthracnose, the most common mango disease, is caused by a fungus (Colletotricum gloesporiodes, Penz) that affects the flower, fruit and leaf as spots and fruit rot. These infections show up as brown spots in the flowers and panicle that grow in size and number, eventually causing the death of the flower.

On the leaf, the disease starts as small, dark angular to irregular spots that merge together forming large necrotic areas that may crack or break away.

And young fruit is readily infected. Spots vary from small pinpoints to large in the wet weather. This stage is responsible for the decay of mature fruits. When maturing, the infected fruit will have black spots, which may be swollen and cracked, penetrating deep inside the fruit.

Scab is caused by the fungus Elsinoe mangifera, Bit and Jenkins. It mainly attacks young, expanding tissues on blossoms, leave, twigs and fruits. Infections are nearly circular spots 1mm to 2mm in diameter, dark brown to black in color. Severe infections will cause distortion of the leaf, followed by defoliation.

Powdery mildew is caused by Oidium spp. and results in red rust and algae spots; stem end rot; and verticulum wilt. Most of these diseases can be controlled with fungicide applications in a spraying program to prevent their development.

Insects, mites and other pest: Scales are caused by a number of organisms including Pinnapis spp., Pseudaulapsis cockerelly, Pseudococcus citrii.

Mite species infecting mangoes are Olygonynchus spp. and Tetraninchus. Trips are Selenothrips rubrocinctus. Ambrosia beetle is Xylosandrus compactus, or Diabrotica baltaeta.

Fruit flies are a problem in Middle Guinea more so than Upper Guinea. The so-called "papaya" fruit fly is Toxotrypara spp. and the Caribbean fruit fly is Anastrepha spp.