Mango

Land Preparation: Mango

Mango thrives well in a wide range of soils. Root system is deep and laterally well spreading. Hence. Deep soils of about 2 m deep with good drainage capacity are very favourable for establishment of mango orchards. Optimum pH level is between 5.5-7.5. Mango trees will not perform well in areas where water table fluctuates frequently. Hence, it is better to select areas with water table at more than 3 m depth.

Planting: Mango

  1.1. Propagation

Mangos are propagated mainly by grafting. The selection of suitable rootstock is as important as the selection of the scion cultivar variety, type. It has a strong influence on the growth, yield, fruit maturity stage of final fruit development (ripeness) and soil adaptability, among other things.

In Rwanda, the uniform seeds of the polyembryonic cultivar Dodo are routinely used successfully. Seeds must be taken from ripe fruits and should be as fresh as possible at the time of planting. Before planting, the hard woody endocarp should be removed to examine the seed for disease or any damage caused by the mango weevil. Freshly sown seeds should be protected from high temperatures and dessication by providing shade. Once seedlings emerge the shade is removed to harden the plantsjoining parts of plants together such that they will unite and continue their growth as one plant. The rootstock should be fertilized, watered and grown to the diameter of a pencil prior to grafting

1.2. Grafting

Grafting is the most reliable and economical means of propagating the mango. It consists of transferring a piece of a mature, bearing tree (scion) to a separate seedling tree (rootstock), forming a permanent union. The scion forms the canopy of the tree, while the rootstock forms the lower trunk and roots.

Grafting success involves the intervention of trained horticulturalist or agronomist. The farmer who wish to graft his/her mango trees will seek assistance from the above mentioned professionals or buy grafted seedlings from them.

2. Planting

Dig holes 80 cm deep and 80 cm wide while separating top soil from sub (red) soil. Mix well decomposed manure (50 kg/tree) with top soil and put back into the hole. Make a small hole within and plant in the grafted seedling. The plastic bags used for potting should be removed before planting. When covering the hole a basin should be made around each plant for harvesting water. Each plant should be mulched. One month after transplanting, the grafting tape should be removed. Any shoots, which grow below the point of union should also be removed. Normally, grafted trees are spaced at 4-5 x 4-5m, plant density of 400-625 plants/ha.

Crop management: Mango

1.1. Fertiliser Requirements

A general criterion regarding mango nutrition is that care must be taken not to over-fertilize thereby promoting vegetative vigour at the expense of flowering and fruit set. This is particularly true for nitrogen application since trees are subject to fertilizer burn. The table below shows the recommended nutrients per one mango tree and fertilizer per one mango tree per year. Well-decomposed organic manures are recommended at the time of planting.

Table. Nutrients recommendation per one mango tree (g/year)

Year	N	P	K
1	70	25	200
2 to 3	140	50	200
4 to 5	210	75	250
6 to 7	280	100	375
8 to 9	350	125	500
10 or more	420	150	625

Table. Fertilizer recommendation per one mango tree (g/year)

Year	NPK (17-17-17)	Urea (46-0-0)	KCl (0-0-60)
1	147	98	292
2 to 3	294	196	250
4 to 5	441	293	292
6 to 7	588	391	458
8 to 9	735	489	625
10 or more	882	587	792

Micronutrients B, Cu, Fe, Mn, Mo and Zn are essential for mango plants. Boron deficiency results from excessive leaching, overliming and excessively dry weather.

Tabel. Recommended concentrations for foliar sprays

Deficient nutrient	Treatment
B	Solubor at 300 g/100 l water
Cu	Copper oxychloride at 200 g/100 l water
Fe	chelate/sulphate applied
Mn	MnSo4 at 200 g/100 l water
Zn	ZnO at 200 g/100 l or NZN at 150 ml/100 l water

1.2. Pruning

Mango plants should develop into strong well-shaped trees within the first 4 years and do not require pruning unless there are excessive branches or the shape is unusual. Depending on the cultivarvariety, type and growth pattern, selective pruning of branches may be required to encourage growth of lateral branches and to ensure development of good tree architecture for future fruit bearing. Being an evergreen tree, bearing flowers on past seasons shoots terminally, regular pruning is not advisable in mango. Any branches on the trunk the main stem of a tree lower than one metre from the ground should be cut. In later years, pruning is done mainly to remove diseased and/or dry branches or those touching the ground or crowding others.

A large number of trees become unproductive in due course because of dense and overcrowded canopies, which reduce light interception and utilization by the photosynthetic surfaces. Favourable effects of different intensities of pruning in mango on light interception, chlorophyll content in leaves and yield have been reported.

 1. 3. Irrigation

The tree itself is not difficult to grow and, once well established, is relatively tolerant of drought, occasional flooding and poor soil condition. Irrigation in the first years after planting promotes flushing (and suppresses flowering), so that tree size increases quickly. Irrigation at a frequency of 4-5 days is sufficient for this purpose, the frequency being dependent upon the soil moisture condition. Irrigation also widens the scope for intercroppingthe growing of two crops simultaneously in the same field, for example with pineapple or vegetables, during the establishment phase.

About 2-3 months prior to flowering, irrigation should be withheld, otherwise decrease in flowering and promotion of vegetative growth will be resulted.

However, it is proved that watering at an interval of 10-15 days during fruit setting and development period is advantageous to reduce fruit drop and to increase fruit retention, size and to get better quality.

1.4. Intercropping and weeding

There exists no hard and fast rule in selecting intercrops suitable for mango orchard. Any short duration crop relevant to the specific location can be selected. Some of intercrops suitable include vegetables, pineapples, strawberry, etc. Whatever the crop selected, intercrop and main crop must receive separately their independent requirements of fertilizer and irrigation. Intercropping results in increased humidity and vegetation in orchards that may promote infestation of pests and diseases in greater intensity than under clean cultivation. Therefore, regular plant protection measures are to be carried out as a need base practice.
Keeping the mango orchard clean form weeds is a general rule to get better establishment. At least one shallow cultivation at 3 months interval will be sufficient for controlling weed growth. Bearing mango orchards are to be kept free from excessive weed growth either by manual weeding (or slashing) or by using some weedicides. Where mulching materials are available, mulching is encouraged.

Pests and diseases management: Mango

The primary insect pests of mangoes are the mango fruit fly and the mango stone weevil. The two most serious fungal diseases of mangoes are powdery mildew and anthracnose.

1.1. Anthracnose

Caused by the fungus Colletotrichum gloeosporioides, is undoubtedly the most common and widespread fungus disease of mango and is a major factor limiting production in areas where conditions of high humidity prevail. The fungus invades inflorescences, fruits, leaves and twigs. Substantial losses due to this disease are recorded every year not only at premature stages of the crop but also during storage after picking.

Symptoms:

The signs are visible as small black spots which later get bigger. When the germ affects the flower, some may wither and die before fruit set.  Infected young fruits show very small, brown or black, sunken spots. The disease goes into an inactive stage until fruits are harvested. Afterwards, the fruits develop round, black sunken spots and eventually the whole fruit rots.

Management:

To control untreated subjects used for comparison with those given a particular treatment the disease, orchard sanitation and pruning of dead twigs and branches which may harbour the fungus are the principal control measures used to reduce the source of a new infection cycle.

The widespread occurrence of the inoculum of the fungus makes it impossible to control the disease by pruning and the removal of dropped leaves alone. To be more successful, the above mentioned measures have to be supplemented by spray applications using Mancozeb, copper oxychloride, Maneb, Propineb, Benomyl etc.

It is recommended to start spraying at the stage of flower-bud formation. During flowering/fruit set and until the fruits have developed to half their size, spraying should take place at fortnightly intervals. After this, it is sufficient to treat the trees once a month. It is very important to apply a full cover spray for the first two applications.

1.2 Powdery Mildew

The powdery mildew disease, caused by the fungus Oidium mangiferae, is a serious problem in all mango-growing areas. Infections can result in complete crop loss and defoliation of trees. The disease favours cool and cloudy weather but also occurs in warm and humid climatic conditions. It attacks leaves, buds, flowers and young fruits. Infected tissues are covered with a whitish, powdery growth of the fungus. Mature spores are easily blown away by wind and produce a fresh infection, or they may remain dormant alive but not growing; a resting stage during the unfavourable season awaiting optimum germination conditions in the next season.

Photos: Powder mildew symptoms on inflorescence, young and older leaves

Management:

• Non-chemical control:

• Prune the tree for excessive branches  for light and air flow, and to keep them short for easy management.
• Avoid mixing in the same field highly susceptible varieties like Bolibo with tolerant ones like the ones listed below.
• Plant torelant varieties like Sensation, Tommy, Kent, Bire, Zillate  and Van dyke.
• Plant wind breakers around the mango orchard (live fencing of Kei apple tree can be used). Winds accelerates the spread of the disease powder.

Chemical control:

• If spraying is possible in your orchard, spray sulphur based fungicides (e.g. Thiovit/Thionil) 3-5 times at intervals of between 10-14 days from new flush tending to flowering until fruit set if confirmed.
• Other fungicides include Mancozeb, Benomyl, etc.

1.3. Mango Fruit Fly

Different types of fruit flies are known to attack ripening mangos in almost all mango-producing areas. Yield losses of more than 50% have been reported. Ceratitis cosyra followed by C. rosa and C. capitata have been found to be the major pests of mango.

The females lay their eggs under the surface of the fruit skin. After hatching, the maggots penetrate the flesh and destroy the fruit from inside. The infested part becomes mushy and causes premature colouring of the already useless fruit.

Photos. Adult and larva of mango fruit fly (©A.M. Varela, ICIPE)

Management:

Non chemical method:

• Pick and destroy all fallen and cracked fruits on the ground and from the tree and bury them (50cm deep) throughout the season (atleast twice a week).
• Dig the ground below the tree canopy to expose the insect (maggot and pupa) to sunlight and predators.
• Farmers must not mix late maturing varieties (e.g. Kent and Zillate) with early maturing varieties (e.g Bire, Tommy  and Apple mango).  in the same field because late varieties are attacked by the population that builds up during the ripening of early varieties
•  It is important to manage insect pests in alternative hosts such as guava, citrus, cherimoya and papaya near the mango field.
• Regular orchard sanitation
• Determination of population density by using traps
• Regular poison-bait applications

Chemical method:

•  Spray entire tree every 2 weeks with cypermethrin (e.g Rocket) at 1ml per 1L of water from December onwards and late July onwards until 2 weeks before harvest.
•  Alternate abamectin (e.g. Dudu abamectrin) at 1ml/1L with cypermethrin (above). Follow spray interval and period as above

1.4. Mango Seed Weevil

The weevil, Sternochetus mangiferae (F), is a common pest and can be found in all local mango-growing areas. It is spread mainly by transportation of infested fruits since the weevil develops within the mango seed and can therefore be transported easily from one locality to another unnoticed. The mango weevil does not usually damage the fruit and consequently is not a serious pest as far as local consumption of the fruit is concerned. However, this pest hinders the development of a fresh fruit export market because the leading import countries in the Middle East and other places maintain strict quarantine the prevention of importation or exportation of unwanted organisms into a territory regulations.

Infestation symptoms are most obvious within the seed where the weevil largely completes its life cycle. Externally the affected fruits appear normal, but very often are rotting from inside.

Photos: Larva and adult of mango seed weevil (©Peter A. Follet; Monique H & Biovision)

Management:

To date, chemical control untreated subjects used for comparison with those given a particular treatment measures against this pest have not proved economical. However, implementing the following three steps will definitely reduce the weevil population in the orchard.

Sanitation of orchard and yard: The biggest source of infestation is dropped fruits or seeds lying around in which weevils can survive up to about 300 days. Therefore, regular removal and destruction of waste material up to the end of the harvesting period is very important and effective.

Treatment of trunk and branches: The most suitable stage for control is during the emergence and oviposition of the adult weevil. The first step to suppress the weevil population is implemented at the beginning of the mango flowering season by using preferably long-lasting contact insecticides. It is important to thoroughly wet (by spraying) the bark of the trunk.

Fruit treatment: After fruit set, carry out spray treatments mainly focused on single fruits using Cypermethrin, etc. mixed with a spreader/sticker material added to a spray to increase retention on plant foliage liquid. Repeat applications at intervals of 2-3 weeks and combine this with the control of anthracnose.

1.5. Mealybugs (Rastrococcus spp.)

They suck sap from tender leaves, petioles and fruits. Seriously attacked leaves turn yellow and eventually dry. This can lead to shedding of leaves, inflorescences, and young fruit. Mealybugs excrete honeydew on which sooty mould developed. Heavy coating with honeydew blacken the leaves, branches and fruit. This reduces photosynthesis, can cause leaf drop and affect the market value of the fruit.

A wide range of natural enemies attacks mealybugs. The most important are ladybird beetles, hover flies, lacewings, and parasitic wasps. These natural enemies usually control mealybugs.

However, mealybugs can cause economic damage to mango when natural enemies are disturbed (for instance by ants feeding on honeydew produced by mealybugs or other insects) or killed by broad-spectrum pesticides, or when mealybugs are introduced to new areas, where there are no efficient natural enemies.Insecticides do not generally provide adequate control of mealybugs owing to their wax coating.

Management:

• Destroy affected parts at the beginning of the infestation.
• Conserve natural enemies.
• Avoid excessive spraying and the use of broad-spectrum pesticides, since they may kill natural enemies.
• Control ants tending mealybugs.
• When necessary spray only the affected branches/trees (spot spraying). Mineral oils, neem products and soapy solutions (1 to 2%) are reported to give satisfactory control of mealybugs.

1.6. Mango leafcoating mite (Cisaberoptus kenyae)

The mango leaf coating mite is tiny (about 0.2 mm), light colored and cigar shaped. It cannot be seen with the naked eye.  The mites leave in groups under a white coating on the upper leaf surface. The white coating can be easily rubbed off by hand. Leaves covered with the white coating tend to turn yellow and drop prematurely. In general, the coating has minimal effect on fruit yield.

Management:

• Remove and destroy leaves with white coating
• Usually no further control measures are needed

Harvesting: Mango

Mango fruits become ready for harvesting 90-100 days after set. The mature green fruits are to be harvested and ripened under ambient conditions. Leaving fruits on the tree for ripening may result in spoilage of fruits by birds and also such fruits will not stand storage conditions.

Harvest mature fruits and with smooth, undamaged skin. Use a long stick with a knife and basket at the tip or just long stick with knife and clothes or polythehe spread below, off ground to trap falling fruits for tall trees. Collect fruits in a wooden box with smooth inner surface. Avoid picking fruits from the ground. The economic bearing period of mango tree extends up to 40 years.

Post harvest Management: Mango

Mangoes are a delicate fruit and, therefore, sensitive to transport, which limits trade opportunities. After the harvest, mangoes are sent to the market or processing plants for sale as raw fruits or raw materials for juice making plants. Also, there is considerable market interest in processed mango-in pulp or dried form.

Mangoes are eaten raw or processed into delicious juices, either alone or blended with other fruits.