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Cocoa (Theobroma cacao)

Cocoa is a tropical crop. It is popularly grown in West Africa where Ghana and Nigeria are amongst the leading producers, Cocoa is believed to have been introduced into Nigeria from Fernando Po (Portugal) in 1874. The beverage crop is a native of the forest of Amazon and Orinoco in Southern Mexico from where it was introduced into other parts of the world, for example, Asia and Africa. Cocoa is grown in Western states like Ondo, Edo, Ekiti, etc. Cocoa is classified into three distinct groups within the species Theobroma cacao namely:

(i) Criollo group: This species of Theobroma cacao has yellow or red pods when ripe and its wall is thin in section. The pod can be pressed by hand press. The beans normally ferment quickly and give rise to the highest quality of cocoa. The yields are generally low and the trees are poor in vigour and growth and are also prone to diseases. Criollo group is further divided into two sub-species.

(a) Central American criollo: In this type, the pod wall is green when unripe and yellow when ripe. This type requires little or no fermentation and were originally cultivated in central America and Mexico.

(b) Venezuelan criollo: These vary in colour, shape and size. The unripe pods are usually red and ripen into yellow.

(ii) Amazon forester group: The unripe pods are whitish or green and pods turn into yellow when ripe. The seeds are usually flattened. The pod walls are relatively thick and cannot be pressed open by hand pressure. Hence, it requires knife to break it open. The trees are generally hardy, being more
vigorous and high yielding than criollo. They are able to tolerate mild attack of virus.

(iii) Prinitario group: This is a cross between Criollo and Amazon forester. It consists of wide range of hybrids. The unripe pod may be whitish green, red or purple, ripening into yellow, orange or red. The beans vary from plumb to flat and the cotyledon range from white to nearly black colour.

Environmental requirement
The crop is a native of the forest lowlands of the humid tropics. Thus, it is cultivated between latitudes 20 degrees North and South of Equator where climate is usually warm and humid. Cocoa requires a temperature range from 15-30 degrees C for optimum growth and development. Flowering and fruit setting are affected by temperature and fluctuation in mean annual temperature should not exceed 10 degrees C. Temperature should be fairly constant to promote maximum yields.

Cocoa requires a mean rainfall that ranges from 1000mm-1250mm for optimum growth. It still grows well at higher range of rainfall of 2000mm or above, and it requires a high relative humidity. The soil for cocoa production must be deep and well drained with relatively large amount of clay in order to conserve water during the dry season. The quality of litter on the top soil must also be rich in organic matter. The most suitable soil for cocoa cultivation is clayey loam. Sandy loam may be used but if the climate is dry, production will be low.

Soils that are too clayey or too coarse are unsuitable. Waterlogged soil may be harmful as it promotes incidence of black pod disease and other fungal infection. Cocoa requires a soil pH range from 5.5-7 and the pH below 4.5 is not ideal for cocoa cultivation. If the soil’s alkaline is at 8.5, cocoa leaves become chlorotic (pale yellowish due to loss of chlorophyll). The soil must generally be rich in Nitrogen, phosphorus, calcium and Magnesium. Potassium is not a problem, and usually available in the soil because the leaves which fall off from the plant supply potassium continually.

Generally, Cocoa trees have low heights, which range from 5-10m. The trunk bear the leaves and also lateral branches. The flowers are whitish or yellow. The pods are usually green and in all varieties, the pod turns yellow when ripe.

Propagation
Cocoa is propagated by seeds and by vegetative means including budding, grafting cutting and air layering.

Nursery practice
Cocoa seeds germinate easily (no dormancy) between 7-10 days after sowing. Cocoa seeds are better stored in pods (up to 4 weeks). Cocoa seeds may lose viability if stored for more than a week after extraction from the pod. Extracted seeds could be stored for 2-3 days in moist sand, moist ground charcoal, and saw dust.

Nursery seedling should be carried out between November-February so that seedlings would at least be allowed for 4-8 month before transplanting. The nursery may be done using bamboo places, palm fronds or raised on ground bed in polybag trays at a selected site, that is, near a water source.

In the nursery beds, seeds are sown singly per hole usually 15-20mm deep and at a distance of 15-16cm apart followed by light watering. In the polybag nursery, the polybags are filled with forest top soil or with sand mixed with top soil. These bags are heavily watered a night before. Seeds are sown, one seed is planted per bag.

Adequate moisture content is usually important for the germination and establishment of the seedlings and it should be provided after germination, preferably in the early morning and evening hours, depending on the amount of rain. When the seedlings have germinated, they should be provided with shade; these shades must be gradually removed 21 days before transplanting to harden the seedlings for field conditions. Transplanting should be done in Mid-May to June. There is no need to apply fertiliser to cocoa seedlings in the nursery.

Vegetative propagation in cocoa
(i) Rooted cuttings:
Rooted cuttings are important, especially in Ghana, where polybag method is used. In the selection of cutting, hardened fans are preferred for vegetative propagation. Trinitarian and upper Amazon clones are considered as the best rooters owing to many years of practices. The cutting must have about 3-4 leaves on it and it is usually cut in the morning hours. They should be wrapped in polythene bags and placed in a bucket on water. The leaves on the cuttings should be trimmed to about 1/8 to reduce water loss. Before setting the cutting in the nursery, the cuttings will be given a fresh cut and dipped in rooting hormones such as indole butyric acid (IB A). The hormone mixture is usually made up of 5 grammes of 5% I. B. A in 50 cubic litre (50cl) of butanol or ethanol, plus 50cl of water. The dipped cuttings are then planted in polythene bags or pot filled with partially decomposed sawdust or top soil. Make a hole at the centre of the polybag and put the cutting at a slanting position. The cutting is then completely conversed with a plain translucent polythene sheet to raise the temperature and keep away insects. After 25 days, the cuttings must have germinated. The polythene material is then gradually removed. The seedlings are transferred to shaded nursery beds for 3 months to facilitate the rooting and foliage leaves development of the cuttings in order to be transplanted to the field.

(ii) Budding:
It is widely used, but not as commonly as rooted cuttings. Budding is carried out by the use of a vigorous root stock, It yields a higher percentage of cocoa.

(iii) Air layering:
Air layering as a vegetative propagation method, which may be used in cocoa production, is carried out using branches. Selected from the desired stem (chuppons), a ring of dimension 15-18 inches is made below the terminal bud. The ring should be 2-3 inches long. The ringed area is then covered up with sawdust and wrapped with polythene sheet. After about one month roots will develop from this area. Then two side ways (i.e. oblique), sloping cut below the rooting zone and allowed to stand for a week. Then, it is completely cut off from the parent plant and planted in polythene bags for about 3 months after which they are then transplanted to the field. Root development may be stimulated by the application of a synthetic growth regulator to a point from the cut branch.

(iv) Grafting:
This method is usually done by taking seedling plants aged 12-18 months in containers. The root stock seedling and scion seedlings of almost the same diameter are then placed closely and the two are grafted together. This procedure requires about 3 months for the graft union to form after which the graft can be separated from the parent plant followed by a month of hardening off. The whole process requires a minimum of 18 months.

Field Planting
Site selection and land preparation: The selection of site is a major factor in cocoa production. Cocoa requires a favourable climate and soil for optimum yields. If the forest area is considered, the land may be clear felled, but this operation is not ideal in small-scale production.

This involves the cutting down of all the large trees. The smaller trees and shrubs are left to provide shade. Lining out and pegging: The spacing is normally 3m x 3m, pegs are pinned at the spots to be holed and the holes should be 15 x 30 x 37.5cm.

Transplanting
Cocoa is transplanted into a well prepared land after they have grown in the nursery for about 4-5 months and when rains are constant (May-June). When planting is carried out in a forest land, selective felling of trees is adopted. The larger trees are cut at 3 metres interval to reduce their numbers. The smaller trees are not tampered with. This is because these trees are to provide shade for the seedlings. These shades are removed between 2 and half to 3 years.

In ground bed nursery, seedlings are lifted with a ball of earth where the planting site is near the field. However, naked roots of seedlings are dipped in clay slurry and the seedlings are immediately planted in the field on arrival to the planting sites where long distance transportation is unavoidable. After long distance transportation, polybag seedlings are allowed to regain vigour for a week (7 days) before transplanting. The most ideal period for transplanting is May-June, although it can be done in April, in Eastern Nigeria.

Note: Polybag seedlings do not require special treatment because the planting site is near the field.

Field maintenance
The field maintenance practices in cocoa production include:

(i) Provision of shade is required during the establishment phase (2-3 years) before the canopy closes. Ideal shades are usually provided to protect the seedlings from intense sunlight. The shade chosen must in the least compete with the cocoa seedling for water and nutrients. The shade trees include plantain, glyricidia, erithryna. Plantain is often used but banana should be avoided because it serves as alternate hosts to pests and disease pathogen affecting cocoa. Palm fronds are also used for construction of temporary shade for young plants. However, with adequate climatic and edaphic (soil) factors, shading tend to be unnecessary. Based on this, Amelonado tolerates more shade then a typical Amazon.

(ii) Mulching: Mulching in cocoa field is done in October, before the rain ceases, transplanted plants are mulched 60cm-90cm wide with about 15cm deep layer of mulch placed 15cm from the base of the tree. Either grass or polythene materials are normally used as mulch material, but the former is preferred for its cheapness and also adds organic matter to the soil. However, polythene sheet is more effective in water conservation and weed control.

(iii) Weeding: Clean weeding is usually done on small-scale holdings. In large scale production where large fields are involved, row weeding is carried out three times followed by 4-5 slashing of the fields for optimum weed control. Weeding is practiced because it reduces the incidence of the black pod disease as it allows for better circulation of air, thereby helping to reduce the humidity within the cocoa plots. It tends to also help in the control of insect pests. Chemicals, which are formulated herbicides, can also be effectively used for the weed control. These herbicides are simazine, paraquat, Amino Triazole.

(iv) Pruning: Pruning is carried out between May-June, when the cocoa trees are 2-3 years, using sharp cutlass. This is done so as to remove the chuppons and young flushes in the stem or branches. Stem pruning saw is normally more efficient in the pruning process.

Regeneration
Cocoa trees are usually damaged by rainstorms or strong winds, dormant buds grow out rapidly. Regeneration occurs from the base of the damaged cocoa tree with emergence of dormant buds from the base part. These buds which develop are usually three which regularly separate at the base of the trunk but one, or at most two, is retained, and earth is heaped around the new shoot to promote the rapid growth of an independent root system.

Another method is referred to as coppicing. Under this method, the trees in half of the field are out of planting position and allowed to sprout. Vigorous sprouts are selected and put on proper condition till they start bearing, before the other half is also cut down. Regeneration is an important field maintenance operation aimed at optimum yields of cocoa in a field.

Nutrient requirements
Cocoa requires a routine application of fertiliser containing Nitrogen, Phosphorus, potassium and magnesium (I. e N. P. K Mg.) from the first two years to the 5th year of establishment in a field:

(i) For the first two years, 100 -200kg of urea or 200kg N.P. K Mg should be applied.
(ii) 3-4th year, 200-250Kg of N. P. K. Mg.
(iii) 5th year and upward, 150-250Kg urea or 500-600Kg N.P.K. Mg. These nutrients could be applied by ring or broadcasting method.

Harvesting
Cocoa starts to produce fruits at 4-5 years up to 35 years. Harvesting is carried out with sharp machetes, harvesting knife with short knife handle, or harvesting knife on poles, depending on the height the tree attains. Sharp knife should be used to avoid damage to the bark of the tree and the flower cushion. Harvested pods are conveyed to desired area, using baskets or any good container.

Processing
This involves breaking of pods, fermentation and drying, grading and storage.

(i) Breaking of pods: Pods are broken by hitting them against hard objects to remove the seeds and the mucilage contained in the pods. The extracted seeds are carefully packed in a clean container, normally a basket, after selecting immature seeds, seeds from diseased pods, broken husks, dirts as well as the pulp.
(ii) Fermentation: This is the most important operation carried out in the course of processing cocoa beans for commercial purpose. Fermentation is essential because it helps to kill the embryo of the cocoa beans and prevent germination. It speeds up the removal of pulp, hence reducing the length of drying period. Fermentation process also helps to loosen the testa or skin of cocoa to hasten up the removal of seeds during industrial process, makes the embryo crisp and soft, and as well as gives it a peculiar flavour, taste and colour.

Fermentation methods: The different fermentation methods of cocoa beans include:

(a) Heap method: This method of fermentation is employed locally. The wet beans are packed together to form heaps of about 60-90cm high, using perforated banana leaves placed on the floor. The heap is then covered with more banana leaves and logs of wood, or pieces of banana stem are placed to weigh them down. This procedure enables heat to be generated inside, thus causing fermentation to take place. At interval of three and fifth days, the cocoa beans are usually stirred with a stick to speed up the fermentation process till the seventh day when fermentation is completed. Heap method is an ineffective method that is not employed on commercial scale, because it is labour- intensive.

(b) Basket method: Basket method is normally employed in the fermentation of cocoa beans. The basket is placed on a platform after the basket has been filled with cocoa beans; it is then lightly covered with leaves and supported with stones or logs of wood. The beans are stirred at intervals of 3rd and 5th day and quickly turned into new baskets and then covered once more to conserve heat inside the basket. Fermentation of the cocoa beans is finally completed on the seventh day.

(c) Sweat box method: This is an improved method used in most large plantations. It involves the use of three boxes with perforated bottoms. A detachable side is made of hard wood, and the boxes are 90 x 90 x 90cm, 120 x 90 x 90cm or 1 m x 1.5m x 1.2m sizes. These are placed on a raised platform. The first box is positioned at a higher level. The topmost box is filled with seeds and covered with sack. After 48 hour (i.e. 2 days) slide the detachable front and turn the seeds into the second box and after another 48 hours turn the seeds into the third box. After 3 more days, it is due for drying.

(d) Tray method: This is the best method for fast and efficient fermentation of cocoa beans, and is extensively used as standard practice in many cocoa estates in Nigeria. Trays are constructed with hardwood 75 x 75 x 10cm or 120 x 90 x 10cm. The bottom is perforated (with wire mesh or woven palm frond). The first tray is placed on a wooden platform to enhance drainage. More than 10 or more trays filled with beans are stacked one on the top of the other to a desired height for handling. It does not require stirring or turning. Fermentation is completed in 4 days. It is the quickest, most efficient, takes less labour and yields good quality beans.

(iii) Drying of fermented seeds: Drying prevents the trend of biochemical reactions, hardens the beans and distorts the growth of mould while in storage. Sun drying or drying artificially by burning petroleum fuel or wood generates a lot of heat that helps to keep moisture content below 10%. Sun drying is relatively cheap and easy to carry out. Drying must be done gradually to avoid wrinkling of beans, and to attain uniform drying. Sun drying can be done on concrete platforms and on raised platforms. Drying area must be free from contaminants.
(iv) Grading: Grading is the practice whereby fermented beans are selected according to their quality. It is usually done through random sampling from a bulk of beans and finally 300 seed discrete weight that is not less than 300g. Grade 1 is composed of the beans that have less than 3% slaty seeds, less than 3% mouldy beans and less than 3% foreign materials. Grade 11 consists of the beans that have less than 5% slaty beans, less than 3% foreign materials.
(v) Storage: Graded fermented beans are kept in large sacks and stored in a dry area. It is proper to avoid the direct contact of the sacks or bags with the concrete floor. It might increase the moisture content.

Uses of cocoa

(i)   It is made into chocolate for biscuits, crackers and flavored dessert.
(ii) It is used in coating ice-cream.
(iii) It is a valuable ingredient for beverages – bournvita, etc.
(iv) As cake fillers used in cake industries.
(v) Stimulant theobromine can be extracted and used for drugs.
(vi) Manufacture of medicinal powder.
(vii) For body cream.
(viii) Husks for feeding livestock -cattle, etc.
(ix) Made into thin syrups.
(x) Sweeten fermented wines and other types of alcoholic drinks.

Cocoa diseases

(a) Swollen shoot disease

Causative agent: Virus.
Transmission: It is transmitted by mealybugs that infest the healthy plants.
Symptoms:
(i) Appearances of red vein network which causes chlorosis.
(ii) Swelling of the roots and shoots.
(iii) Mottling of pods.
(iv) Stunted stem and root growth.
(v) Reduction in yield.
Prevention/control:
(i) By breeding resistant varieties.
(ii) Cutting and burning affected parts of the tree.

(b) Black pod disease

Causative agent: Fungus
Species: Phytophthora palmivora.
Transmitted: It is transmitted by rain drop, infected knife, infected soil, insects and rodents that are in contact with healthy pods.
Symptoms:
(i) By removal of infected pods and burning promptly.
(ii) By practising regular weed control.
(iii) By spraying with fungicides e.g. perenox Bordeaux, Brestan, cocoa brasandoz and sandoz.

(c) Die-back

Causative agent: Fungus.
Species: Calonectria regidiuscula.
Transmission: It is transmitted by capsize and Derides, which infest the tips of cocoa tree.
Symptoms:
(i) Rapid defoliation of leaves.
(ii) Reduction in yields.
(iii) Death of branches.
Prevention/Control:
(i) By spraying chemical e.g. Gamalin 20 to dill the Mirids, prime spore-bearing trees.

(d) Charcoal Rot

Causative agent: Fungus.
Species: Botryodiplodia theobromae.
Transmission: Transmitted by infected pods.
Symptoms:
(i) Appearance of dark-brown colour on pods
(ii) Grey colour changes to a deep-black.
(iii) Tiny pustules become exposed.
Prevention/Control:
(i) No control measure yet discovered.

Other diseases of cocoa include cushion gall, root disease, collar disease, etc.

Pests:

(a) Cocoa Mirids or capsid include: Brown Mirid (sahlbergella singularis), Black Mirid (Distantiella theobromae), Cocoa mosquito (Helopeltis betgrolthi).
(b) Mealy bug 13 species
Planoccoides (Pseudococcus njalensis)
Fusariun virgata
(c) Thirips
(d) Stem borer
(e) Termites, coreids pest, etc.

Others are spidermites, black citrus aphids, shieldbug, leaf worms and pod-husk miner.

Prevention/Control:
(i) Spraying chemicals e.g. Gamalin 20, Electron or Rogor, Aldrex 40 or Agrothion.

Cocoa is a crop grown in humid tropics. The most suitable soil for its cultivation is clay-loam. It requires a routine application of compound fertiliser-Nitrogen, Phosphorus, potassium and magnesium.

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