Cocoa (cacao)

Description

Cocoa, Theobroma cacao, is an evergreen tree in the family Malvaceae, grown for its seeds (beans) which are used primarily in the manufacture of chocolate. The cocoa plant is a branching tree with with simple, pointed (lanceolate) leaves which can measure up to 61 cm (24 in) long and 10 cm (4 in) wide. The tree produces clusters of pale yellow flowers each with five petals and sepals. The cocoa pods (drupes) can be green-white, yellow, purplish or red in color each of which contains 20–50 seeds, usually arranged in five distinct rows. The cocoa tree can reach 4–20 m (13-66 ft) in height and can live for up to 40 years although the commercial life of a cocoa tree is usually about 25 years. Cocoa may also be referred to as cacao, koko or Kacao and originates from upper Amazon region of South America.


Uses

Cocoa beans are primarily used in the production of chocolate, cocoa powder and cocoa butter for consumption. Cocoa butter is also used in the cosmetic industry.


Propagation


Basic requirements
Cocoa trees are tropical plants and grow best in humid conditions at temperatures between 18 and 32°C (65–90°F). It is typically grown in regions where daytime humidity reaches up to 100% and night time humidity is between 70 and 80%. The plants require a deep, fertile and well-draining soil with a pH of 5.0–7.5 for optimum development. Cocoa is usually grown in tropical lowland areas is sensitive to drought. It should typically not be grown in regions which experience less than 1 cm of rainfall for periods in excess of 3 months.

Seeds
Cocoa seeds from healthy, ripe pods remain viable for 3 weeks and are usually planted straight after harvest to produce new seedlings. Seeds should be planted in a fiber basket or plastic nursery bag filled with clean soil and placed in a shaded place protected from the sun to prevent scorching. Seedlings grow quickly and are ready to be transplanted after 4–6 months.

Vegetative propagation
Cocoa can also be vegetatively propagated via cuttings, marcotting and budding. Cuttings should have 2–5 leaves and 1 or 2 buds. Leaves should be cut in half before placing the cutting in a pot and covering with polyethylene to allow roots to develop. Marcotting, is achieved by removing a strip of bark from a tree branch and covering the area with a layer of sawdust before covering it with polyethylene. The covered area will develop roots and can then be removed and planted. The final method, called budding, can be used to rejuvenate older plantings and involves excising a bud and positioning it under a flap of bark on another tree. The join is then sealed with raffia and waxed tape. Once the bud begins to grow the tree above the new growth should be removed.

Planting and shading
Seedlings are usually planted in the ground when they are 4–6 months old. The young trees are delicate and require some protection from strong sunlight and wind damage. Protection is usually provided by planting seedlings next to mother trees. This shading also helps to prevent the trees from growing too tall, keeping them at a manageable size for maintenance and harvest. Shade trees are usually other crops such as banana, plantain coconut or rubber. Cocoa seedlings should be planted 3–4 m (10–13 ft) apart and 3–6 m (10–20 ft) from the shade trees. The shading can be reduced once the cocoa trees have formed a closed canopy but some should be retained to reduce water stress and insect damage.

General care and maintenance
The cocoa nursery should be kept weed free while the seedlings established but generally do not require weeding after the trees have formed a closed canopy as the lack of light under the trees prevent any further growth. Cocoa should be supplied with additional nutrients by fertilizing, particularly when trees are grown on poor soils or without shade. Organic fertilizers are generally preferable to inorganic ones as they do not deplete the soil organic content and conserve soil structure. The amount of fertilizer required is dependent on many factors, such as the age of the tree and the amount of shading but mature cocoa generally requires at least 50–100 kg/ha of nitrogen, 25 kg/ha of phosphorus, 75 kg/ha of potassium and 15 kg/ha of magnesium each year.



References

CABI Crop Protection Compendium. (2008). Theobroma cacao datasheet. Available at: http://www.cabi.org/cpc/datasheet/53662. [Accessed 13 November 14]. Paid subscription required.

Jürgen Pohlan, H. A. & Pérez, V. D. (2010). In Verheye, W. H. (ed) Soils, Plant Growth and Crop Production. Eolss Publishers Company Limited. Chapter available at: http://www.eolss.net/sample-chapters/.... [Accessed 13 November 14] Free to access

Crane, J. H., Balerdi, C. F. & Joyner, G. Cocoa (Chocolate Bean) Growing in the Florida Home Garden. University of Florida IFAS Extension. Available at: http://edis.ifas.ufl.edu/pdffiles/HS/.... [Accessed 13 November 14]. Free to access.



Common Pests and Diseases

Frosty pod (Monilia pod rot, Watery pod rot)
Moniliophthora roreri

Symptoms
Spots on surface of immature pods; spots turning brown and rapidly enlarging to cover entire pod surface; disease affects only actively growing pods.
Cause
Fungus
Comments
Causes serious losses in South-Western parts of South America; spores are dry and powdery and are spread easily by water movement, wind or movement of pods; disease spread is highest during periods of high rainfall.
Management
Planting cocoa varieties that produce pods during the dry season allows the pod to avoid the disease; pods showing symptoms of disease should be removed to prevent spread; application of copper containing fungicides will help reduce disease incidence.

Witches' broom
Moniliophthora perniciosa

Symptoms
Characteristic proliferation of shoots and brooms from bud; production of branches which do not produce fruit; distorted pods with green patches which give an appearance of uneven ripening.
Cause
Fungus
Comments
One of the most devastating cocoa diseases in South America; disease is widespread throughout South America, the Caribbean and Panama; spread of disease greatly influenced by humidity with emergence favored by high temperature and high humidity (>80%).
Management
Good sanitation is the most effective method of controlling the disease; material known to be infected should be removed and destroyed; removal of infected material can be difficult as there may be no visible symptoms; new fungicides and resistant cocoa varieties are being developed to help control the disease.

Cocoa pod borer
Conopomorpha cramerella

Symptoms
Holes in cocoa pod husk caused by insect larvae entering and exiting the pod; uneven and premature ripening of pods; seeds sticking together inside pod due to insect eating surrounding tissue; harvested cocoa beans clump together and can be very difficult to remove from the pod; adult insect is a small brown moth; larvae are cream in color and approximately 1 cm (0.4 in) long; larvae change color to green when they emerge from the pod to pupate.
Cause
Insect
Comments
Female moth lives for approximately 5-7 days and can lay 100-200 eggs; eggs are laid on the surface of cocoa pods; larvae develop for 14-18 days before pupating.
Management
Sleeving pods in plastic bags while they mature prevents the insect from reaching the pods, sleeves should be applied when pods are 8-10 cm (3-4 in) long; borer populations can be held in check by black ants and weaver ants; chemical control is often economically unfeasible due to the high price of pesticides compared with the low price of cocoa but, where available, small amounts of contact pyrethroid or carbamate applied to underside of cocoa leaves can keep borers below an economically damaging level.

Cocoa mirid
Distantiella theobroma
Sahlbergella singularis
Helopeltis
spp.
Monalonion spp.

Symptoms
First symptoms appear as tiny puncture wounds on young stems and pods; these punctures quickly turn necrotic, creating black patches which may develop into cankers; discolored bark; terminal leaves and branches dying back; trees unproductive; adult insect is a slender red or brown insect with long legs and antennae; adults are typically between 7 and 10 mm long.
Cause
Insect
Comments
Adult females lay their eggs in the bark of the tree and can lay between 30 and 40 eggs.
Management
In African countries, the insect is usually controlled by chemical eradication programs consisting of two sprays conducted one month apart to target different stages of the insects development; mirids have been shown to be attracted to trees positioned in direct sunlight and providing shade cover in the form of forest to cocoa trees can be used as part of an integrated control method; do not interplant with other hosts such as cashew, tea, sweet potato, guava, cotton or mango - the trees used must be non-hosts; some species of ant, e.g black ants, can be used as a biological control agent.

Cocoa mealybugs
Planococcus spp.
Pseudococus spp.

Symptoms
Flattened oval to round disc-like insect covered in waxy substance on tree branches; insects attract ants which may also be present; insect colony may also be associated with growth of sooty mold due to fungal colonization of sugary honeydew excreted by the insect; symptoms of directinsect damage not well documented but trees may exhibit symptoms of cocoa swollen shoot (see disease entry)
Cause
Insect
Comments
Insects have a wide host range; often tended by ants which farm them for their sugary honeydew secretions; transmit Cocoa swollen shoot virus
Management
Mealybugs can potentially be controlled by natural enemies such as lady beetles but are commonly controlled using chemicals; chemical pesticides may also decrease populations of natural enemies leading to mealybug outbreaks

Black pod (Phytophthora pod rot)
Phytophthora palmivora
Phytophthora megakarya
Phytophthora capsici

Symptoms
Translucent spots on pod surface which develop into a small, dark hard spots; entire pod becomes black and necrotic with 14 days of initial symptoms; white to yellow downy growth on black areas; internal tissues become dry and shriveled resulting in mummified pods
Cause
Oomycete
Comments
Disease occurs in all cocoa growing areas; P. megakarya is most destructive in Central and West Africa whereas P. capsici is most common in Central and South America
Management
Protective sprays of copper containing fungicides in combination with systemic fungicides are often recommended to control the disease; cocoa plants should be well spaced to allow good air circulation through the plantation; mummified pods should be removed and destroyed to reduce spread

Cocoa swollen shoot
Cocoa swollen shoot virus (CSSV)

Symptoms
Swelling of leaves and shoots; red leaf veins, notably in young leaves; chlorotic patches next to leaf veins; chlorotic spots or flecks on leaves mottled, smooth pods with reduced beans; mottled coloration on pods; stems may develop swellings at nodes or internodes and shoot tips; progressive defoliation may occur ultimately leading to the death of the tree.
Cause
Virus
Comments
Only occurs in West Africa. Major problem in Togo, Ghana, Cote d'Ivorie and Nigeria; transmitted by mealybugs. The Swollen Shoot Virus is not native to cocoa but jumped into the cocoa from trees that grew in the rain forests of W. Africa (e.g. Cola chlamydanta, Ceiba pentandra, Adansonia digitata, Cola gigantean and Sterculia tragacantha). The virus is a badnavirus within the family Caulimoviridae.
Management
Infected trees and those surrounding them should be removed and destroyed (up to 5 m from infected tree if less than 10 trees are infected and up to a distance of 15 m if greater than 100 trees are infected) to prevent further spread; a gap should be placed between cocoa plantations of at least 10 m (33 ft) and it may be possible to isolate cocoa plantations using a non-host crop such as oil palm growing between plantations.