Mango (Mangifera indica) belongs to the family Anacardiaceae and is native to India from where it spread to other parts of the world. In Kenya, Mango has been cultivated for centuries especially in the coastal area. In recent years mango growing in Kenya has spread to other regions especially with the introduction of new cultivars.
Mango is an important cash crop especially for small scale growers. Ripe fruits are consumed raw as desserts, or processed into fruit juices, puree, jam, chutney and pickles (canned or dried). The fruit contains almost all known vitamins, many essential minerals (Ca, Fe, Thiamine, Niacin, etc), energy and fibre. Production has been on the rise due to increased demand from the fresh market and processing industry. However, pest and disease damage has been the major challenge to fruit yield and quality.
Mango orchard Ripe Mango fruits
Site selection for mango cultivation is greatly influenced by climatic factors such as temperature, rainfall and humidity.
An ideal climate for mango trees ranges from the humid tropical to the semiarid sub-tropical, wherever a dry period exists of at least 3 to 4 months with sufficient light to induce flowering.Site selected should be of gentle slope (4 - 8%). Steep slopes make orchard activities more difficult and are susceptible to soil erosion.
Specific Ecological Requirements are as follows:
Altitude: 0-1500 masl, depending on cultivar.
Soils: Mango thrives well on a wide range of soils, but a healthy, high yielding plantation is only possible on fertile, deep (at least 3m), well-drained loamy or clay soils with preferably a pH value of between 5.5 – 7.5.
Temperature: For optimum growth and productivity, 20 – 26 oC is considered to be ideal. Pollen viability decrease at 35 °C. Temperatures above 40 0C may, especially in hot/dry areas, lead to sunburn of fruits and stunting of tree growth.
Rainfall: Annual rainfall of 500 – 1000 mm is sufficient. Mango cannot do well in areas which experience frequent rains or very high humidity during the flowering period. Such conditions reduces fruit setting and increases the incidence of diseases.
Clear the field of trees, bushes, weeds and stumps; then prepare planting holes.Ploughing and harrowing may only be needed where intercropping is to be practised.
Prepare planting holes during the dry season, 1-2 months before the onset of rains.
Dig holes 60cm x 60cm x 60cm. Separate topsoil and sub soil. In drier areas, the hole should be bigger (about 90 x 90 cm and 100 cm deep).
Spacing varies from 8m x 8m to 12m x 12m between trees depending on growth characteristic of the individual variety, the type of soil and the agro ecological conditions. Closer spacing of 6 x 4 m or 5 x 5 m could be used within the dry zones where growth is in smaller amount. However, alternate plants should be removed when overcrowding starts to set in. Overcrowding results in the production of fewer fruits which are apt to be poorly coloured and infected with diseases. Overcrowded trees also tend to grow vertically, with minimal horizontal growth. Tall trees present a harvesting problem and create difficulties during spraying and pruning.
In areas with substantial rainfall and rich soils where rich vegetative growth happens, a minimum spacing of 8mx8m is recommended.
In wind prone zones, planting of windbreak rows of trees is necessary.
Mango propagation is primarily done by seeds, especially for the local varieties. Exotic varieties are obtained by grafting a scion on the indigenous rootstock.
Isolate the site to establish a mango nursery as far as possible from existing commercial plantings.
Water to be used should be free of harmful pathogens, nematodes and fungi.
Prepare potting media from any available material as long as it can sustain the life of seedlings.
Take fresh seeds from ripe fruits for rootstock establishment.
The hard, woody endocarp is removed by cutting it open at the narrow end of the seed and forcing the stone off.
The seed itself is then still covered with a loose-fitting parchment layer, which must also be removed.
Sowing of seeds
Spacing: Sow seeds 2 cm x 10 cm in a nursery bed or directly into containers, with the convex edge up and covered lightly with the media. The germination media should be well-drained, examples are river sand, loamy soils, saw dust etc., with seed orientation being the same in each bed.
Preparation of potting media
The following composition is commonly used: 10 parts forests soil; 6 parts well rotten manure; 1-3 part of river sand.
- Carefully lift and separate the germinated seedlings from one another.
- Discard weak plants with twisted tap roots or stems: plant only the healthy plants (not smaller than 6 by 9 inches) in plastic containers.
- Transplant at 4 to 5 weeks old; keep the transplanted seedlings in the shade and carefully tend them.
- Graft when the rootstocks are about 5 to10 mm thick at a height of approximately 25cm.
Take scion wood from healthy well-developed vegetative shoot, without flower buds.
- The best scion material is matured, hardened shoot from upper part of the tree 5 to 7.5 cm long.
- Place the buds of the scion upright on the stock, ensuring correct orientation.
- Protect all cut surfaces from drying and pathogen entry, immediately after grafting.
- Properly label and tend the grafted seedlings for a period after grafting.
After Care Grafting
- Keep grafted seedlings under appropriate shade which does not allow direct ray of the sun: buds will start to shoot after 21 days from the date of grafting; the seedlings are ready for field transplanting 3 months after grafting.
- Protect the graft union from water to avoid entry of pathogen
- Check regularly for moisture content and water if necessary; Conduct regular pest and disease control operations
- Remove immediately any growth from the rootstock; Reduce shade when the tender leaves start to turn green
Remove the tape when the first flush turns completely green; Remove the shade completely when second flush takes place.
There are two types of mango varieties grown in Kenya: The Local varieties that include the Dodo, Boribo, Batawi; and the Exotic varieties that include the Apple, Kent, Keitt, Sabine, among others.
Proper selection of mango cultivars for production has to take into account the following:
(i)Good adaptation to local conditions;
(ii)Tolerance to pests and diseases;
(iii)Alternation of flowering and fruiting;
(iv)Designated use and market requirements.
The main characteristics that differentiates the varieties are the fruit shape, size, aroma, sweetness, colour, fibre content, taste, seed size and resistance to disease. The following are the exotic or improved varieties grown in Kenya:
Advantage: The juicy yellow flesh has excellent flavour and a melting texture virtually free from fibre.
- Susceptible to anthracnose and powdery mildew
- Alternate bearing
- Limited range of altitude adaptation.
- Very attractive fruits
- Has a firm, deep-yellow flesh, medium juice and moderate fibre and pleasant aroma.
- Excellent shipping and shelf life qualities
- Consistent producer
- Good resistance to anthracnose and powdery mildew.
- Fibre content is slightly higher than average
- Danger of internal breakdown.
- Good to excellent fruit quality; Is Fibreless, melting and carries no turpentine taste.
- Excellent for processing
- Good shipper
- Susceptible to powdery mildew
- Tendency of alternate bearing.
- Its flesh is juicy, melting deep yellow, fibreless, with a rich flavour.
- Fruits Ship well.
- Prone to storage diseases
- May exhibit alternate bearing.
- Late maturity
- Good marketing qualities and productivity
- Fair resistance to anthracnose
- Only slightly affected by anthracnose and powdery mildew
- No distinct biennial bearing
- The yellow flesh is of medium texture, fibreless, pleasantly sweet, juicy and of a mild aroma.
- Good resistance to anthracnose and powdery mildew.
- Regular bearer
- Beautifully coloured late cultivar
- Non to scanty fibres
- Heavy yielder
- Excellent fruit quality; It is very juicy with a pleasant aroma.
- Has an attractive appearance and is suitable for commercial production.
- Good shipper
- Because of its good quality, seeds from the Haden variety are used as parent for several other varieties of mangoes.
- Has yellow-apricot when ripe with a deep orange, good quality flesh which is virtually free of fibre.
Advantage: Good to excellent eating quality (resembles haden).
Plant at onset of rains but if there is sufficient irrigation, then planting is possible at any time of the year.
Transplant the grafted trees as per the planting hole specifications made in the land preparation section above.
Apply manure/compost and basal fertilizer as follows:
- Mix top soil with 1 debes (20kg) of well decomposed manure and 125g of TSP/DAP before returning the mixture back to the hole.
- Water the hole just before planting to ensure contact of the roots with moist soil.
- Remove the polythene tube and hold the soil/ media around the roots.
- Maintain the position of the level of soil as it was in the polythene tube while planting and firm the soil around the planted seedling. Planting should ensure all roots are well covered and graft union is above the soil surface.
Water well and mulch after transplanting.
Site specific fertilizer recommendations should be based on soil analysis results.
Mango nutrient requirements include N, P, K, Mg, Ca, Na, B, S, Zn, Mn, Fe, Cu, Al, and Mo.
In the early years of crop development, mangoes require high levels of nitrogen but after they begin to bear, the fertilizer should be higher in phosphate and potash.
At planting, in the absence of a soil analysis report, mix one debe (20-30 kg) of well decomposed manure and 125 g of DAP with topsoil and return the soil to the hole dug earlier to refill the hole. The quantity of manure applied increases with age of the crop; From 1 debe annually to 4 debes each year at an optimum production (i.e. from 7th year).
Top dress with about 150g of CAN at the beginning of each rainy season until the third year when the rate is adjusted. Spread fertilizer or manure around the drip line of tree canopy and mix with the soil.
During flowering, mangoes need high amounts of potassium to trigger flowering, flower retention and good development of fruits. Inadequate potassium leads to heavy flower abortion and unhealthy fruit set and development. To curb this, spray foliar fertilizer with potassium (eg Goldchance Flower and Fruit), weekly, right from the appearance of flower buds.
In drier areas, irrigation is necessary, especially during early stages of growth and development. Planted seedlings should be watered frequently 2 to 3 times per week until the crop establishes fully. Irrigation in the first years after planting promotes flushing (and suppresses flowering) so that tree size increases quickly. Irrigation also widens the scope of intercropping with, for example, pawpaw, pineapple or vegetables, during the establishment phase.
For grown up trees, irrigation is not recommended for 2 – 3 months prior to flowering as it is likely to promote vegetative growth at the expense of flowering. There should be a marked season with dry weather to induce flowering and fruiting. From fruit set to maturity, irrigation at 10-15 days interval is useful for up yield. Irrigation can also be applied to stimulate flowering after a distinct dry spell.
Keep the orchard weed free in the early stages of growth. Once the seedlings have taken off well, break the hard pan formed when irrigating/ watering by shallowly digging at the base of the stem.
In mature trees, weed 2 m strip along the rows and cut grass in the rest of the field. Use as mulch.
Mango trees need continuous attention in order to ensure continued harvests and to improve the lifespan of the orchard trees.
Most important management practises will entail:
-Nutrient application in the form of compost or organic materials, fertilizers and foliar sprays;
-Weeding or mulching;
-Pruning and flower inducement.
-Monitoring pests and diseases for action.
The form and height of a mango tree needs to be controlled to guide the tree and to facilitate harvesting at a later stage.
Formative pruning is done when the seedlings are about 1m high. The central leader is cut off to encourage lateral growth of branches. 3-4 lateral branches are left to grow to about 40cm and are cut off to encourage more lateral branches to grow outwards. 4-5 stories are recommended. This formative pruning done during early stages of growth gives mango trees a spreading (desired) shape that is easy to manage.
Structural pruning - should be done for proper maintenance of the trees; to remove dead wood and to open the canopy. It should be done mostly after fruit harvest. The height of the trees should be controlled to about 3.5 m in height and at this stage, all branches at knee level (about 0.5 m) should be pruned (skirt pruning). Any dead branches and sucker branches should be removed to allow more sunlight through the canopy to the ground under the tree. This should be done every year in order to maintain the tree at 3.5 m and develop a suitable canopy density.
Advantage: Pruning stimulate new growth; promotes uniform annual bearing; controls size; increases light penetration to the canopy; reduces relative humidity within the canopy; creates environment less conducive to disease development; encourages flower bud formation and increases yield (bigger fruits).
Pruning is done when plants are dormant.
Flower inducement can be achieved through the following ways:
(a)Chemical: Spray the trees with 1% potassium nitrate solution at a rate of 2-3 kg/ha (400g/ 20L water).
(b)Smudging: Burn smoky fire below the tree canopy and allow the smoke to pass through the foliage for several days.
Mango smoking improves fruit setting and also reduces insect population drastically.
(c)Physiological stress: Induce physiological stress by
depriving the plants of water for a period of 1-2 months, then irrigate regularly. Alternatively, ring the branches or prune the roots.
Inject with Neonicotinoids/Pyrethrinoids to control abortion and act as a foliar.
Major pests are:
(i)Mango fruit fly
(ii)Mango Seed Weevil
(iii) Mango Gall Midge
(i)Mango fruit fly
Mango fruit fly are yellowish flies that are commonly attracted to fermenting fruits of all kinds.
Fruit Fly larvae Adult Fruit fly
Fruit flies cause direct damage by puncturing the fruit skin to lay eggs. During egg laying, bacteria from the intestinal flora of the fly are introduced into the fruit. These bacteria cause rotting of the tissues surrounding the egg.
The eggs hatch and the emerging maggots feed on the fruit flesh making galleries. These provide entry for pathogens and increase the fruit decay. The fruits ripen prematurely and drop to the ground just before the maggots pupate.
- Collect all fallen fruits and destroy by burying at least 50 cm deep or put them in a drum of water with 1 inch oil for 2 weeks.
- Spray with recommended insecticide eg Deltamethrin. The chemicals can be mixed with hydrolyzed protein or sugar/ molasses and sprayed to act as bait.
- Harvest mangoes before they become ripe.
- Use of natural enemies, especially parasitic wasps
- Post-harvest Treatment (Hot Water Dip): Dip fruits for 5minutes at 50 0C water.
- Use of fruit fly trap such as Auto Dissemination Device
(ii)Mango Seed Weevil
The adult is grayish brown and is usually active after dusk. They hide on the bark of mango tree trunks and pretend to be dead when disturbed.
Seed Weevil larva Seed Weevil adult
Externally the affected fruits appear normal, but very often are rotting from inside. The beetle lays eggs on young fruit. The young larvae penetrate the fruit and eat their way to the seed where they feed and develop into adult weevils. These emerge from the stone by tunnelling outwards through the flesh and skin of the fruit, leaving an unsightly patch where rotting soon sets in. Once the weevils have left the fruit they search for a hiding place such as beneath loose bark of trees or in waste material under the trees.
- Collect fallen fruits and destroy by burying or burning
- Paint the tree trunk with agricultural lime mixture at flowering to prevent adult weevils from climbing up the tree
- Spray biweekly with recommended insecticide eg Deltamethrin. Spray before flowering and during fruit set and repeat every 14 days focused on single fruits.
(iii) Mango Gall Midge
The gall midges are small insects measuring about 3 mm in length.
Mango leaf damaged by Gall Midges
- Adults lay eggs on young tender leaves. The larvae mine the leaves producing dark green, circular galls (swelling tissues/pimples) randomly distributed on the leaf blade
- Under heavy infestations, the leaves wrinkle and remain necrotic and eventually drops.
- Orchard sanitation.
- Clear weedy areas since adults prefer to stay on these plants
- Prune crowded branches (particularly irregular branches) to allow light penetration.
- Conserve natural enemies.
- Spray insecticides e.g Deltamethrin mixed with mineral oil as soon as new shoots and leaves appear.
Small round reddish brown to white insects usually found in clusters on upper surface of leaves, branches, stem and fruit.
White Scales on the Mango Fruits
Damage: Scales suck the cell sap from the infested areas.
- Infested leaves turn pale green to yellow eventually die and drop.
- Infested fruits have pink blemishes and drop.
- Poor growth and dieback of branches.
- Infested young seedlings may die.
- Honey dew is produced which form sooty mold, thus reduction of photosynthetic capacity.
- Cut and burn infested tree parts
- Use of natural enemies e.g. Parasitic Wasps, Ladybird Beetle, Lacewings etc.
- Spray with insecticide mixed with white mineral oils 2% : paraffin oil is sprayed at 3 % water emulsion. Avoid spraying mineral oil during very hot periods of the day.
- Use of D-C Tron (Caltex oil) to suffocate the insects.
Mealybugs are small, flat, soft bodied insects covered with a
white woolly secretion.
Mealybugs on a mango fruit
- 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.
- Insecticides do not generally provide adequate control of mealybugs owing
to their wax coating
- Destroy affected parts at the beginning of the infestation
- Heavily infested branches may be pruned to control the pest, especially on the tender branches before flowering begins.
- Conserve natural enemies.
Major diseases and physiological disorders are:
- Powdery Mildew
- Jelly seed
Cause: fungus Oidium mangiferae.
Powdery mildew on leaves (left) and panicles (right)
Disease infection is favoured by cool and cloudy conditions.
The disease 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.
The white powdery growth turn black later in the season.
- Infected leaves curl and become distorted.
- Infected young fruits have purplish haze.
- Infected flowers and young fruits turn brown and gray and
- Poor fruit set.
- Use resistant varieties e.g. Sensation, Van Dyke, Tommy Atkins (NB: All mango cultivars are susceptible to powdery mildew infestation to some extent).
- Cultural practices e.g. spacing, pruning, sanitation.
- Observe plant nutrition
- Spray 70% Neem Oil
- Spray recommended pesticides (eg Bayleton 25 WP). Spraying 3-5 times at 10-14 day intervals from the onset of flowering until fruit set.
Cause: fungus Colletotrichum gloeosporioides
Most infections occur from the beginning of flowering in gradually decreasing severity until the fruit is about half-grown.
Symptoms: Symptoms occur on leaves, twigs, petioles, flower clusters (panicles) and fruits.
On Leaves, Petioles, Twigs and Stems, lesions start as small angular brown to black spots that can enlarge to form extensive dead areas.
Infections on the flower and panicle appear first as minute brown or black spots which slowly enlarge. Infected flowers usually wither and die before fruit set.
On fruits, spots may remain as pinpoint latent infections or they may enlarge in wet weather. The latent infections on young fruits cause much of the decay which occurs in mature fruits. Nearly mature to ripe fruits will have black spots of varied form which may be slightly sunken and show surface cracks penetrating deeply into the fruit causing extensive rotting or complete blackening of the fruit surface.
- Remove and destroy dead twigs and branches
- Spray recommended fungicides eg Propineb (Antracol®) every 14 days. Start spraying at the stage of flower-bud formation, during flowering/fruit set and until the fruits have developed to half their size. After this, it is sufficient to treat the trees once a month.
- Dip fruits for 5 minutes at 50 0C water.
- Store fruits in a cool place.
All Mango cultivars are to some extent susceptible to anthracnose.
(iii) Jelly Seed
Jelly Seed is a Physiological Disorder caused by Calcium deficiency
- Degeneration of fruit pulp after harvesting fruit, characterized by premature and uneven ripening of the mesocarp.
- Other symptoms include internal breakdown, soft nose, stem-end cavity or spongy tissue.
• Application of dolomitic lime (CaCO3.MgCO3) at the rate of 3.2 tons per acre per year applied once at the onset of long rains.
One tree should produce 200 to 500 fruits per year and varieties like "Dodo" and "Boribo" can produce 1000 fruits per year. Most varieties show biennial tendencies in production and a poor harvest may follow a good one.
Harvest mango fruit at the mature-green stage, when fruits start to change colour, when flesh around the seed also changes from white to yellow colour. If harvested too early quality will be inferior, if too late the storage period is reduced and may get jelly seed problem.
Handle gently to avoid damage to the fruit; Use a ladder for tall trees to avoid pulling the fruit from the tree. Harvest the fruit with long stalk (5cm) and pack in single layer with pedicel facing downwards.
Allow latex that leaks from pedicel to drain on to absorbent material in the bottom of a crate. Wash the latex that drip with detergent e.g. 0.5 % Teepol solution.
Postharvest treatments cannot improve the quality of the fruit but can preserve it.
Stack mango containers well to avoid any movement during transportation. The cartons should be well ventilated and should have a handle for handling.
Harvested Mangoes being packed in card board boxes
Fruit should not rub against each other during transportation
Dip newly harvested fruits into hot water to minimize fruit fly damage and anthracnose. Hot wat++er treatment controls anthacnose disease while fungicide controls soft brown rot
Besides aesthetic value waxing prevents moisture loss and chilling injury.
In the packhouse cut the pendicel to about 5mm . Use sodium hypochlorite to prevent buildup of pathogen; Treat the fruit with hot water at 50 0C for 5 minutes to minimize Fruit Fly damage and anthracnose.
Wash with an appropriate imidazole fungicide like prochloraz at a rate of 150ml/100l water for 10seconds.
Perform preliminary grading to sort: Immature, under sized, damaged, bruised, scorched or ripened fruits are removed during sorting.
Wax the fruits, using polyethylene wax, or any appropriate wax
Pack the fruits in single layer in fibre board cartons, to void rubbing against each other that can shorten the shelf life of the fruits. Mango fruits are sensitive to chilling injury.
Transportation and storage
Transport or store mango at 11oC for green fruit and 8oC for ripe ones. Most varieties can store at temperatures between 10oC and 13oC with relative humidity of 85 to 90% for a storage period of between two to four months.
The first yield at the third year is about 500kg/ha increasing to an average of 15t/ha at the age of seven years.