School Science Lessons
Cocoa Project
Updated: 2009-04-16
Please send comments to: J.Elfick@uq.edu.au
See: Interesting websites
See: Cocoa, Queensland Department of Agriculture (website)
See: Shade-grown cocoa and its environmental dilemma (website)
Preface
Before teaching this project, discuss the content of the lessons with a field officer of the Ministry of Agriculture and get advice on planting material, planting distances, site for planting, approved mulch, composting, and control of pests and diseases. Use only the procedures, agricultural chemicals and insecticides recommended by the local field officer of the Ministry of Agriculture. If you cannot control insects by hand-picking, ask the Ministry of Agriculture to recommend a chemical spray. All insect sprays are dangerous. Show the students how to use them safely. Do not get the spray onto your hands. Do not breathe in the spray. Wash your hands well after using spray. Keep the spray container in a safe place where students cannot get it. Spray on a day of no wind but if you must spray when there is a wind, spray down wind. Make sure the spray does not blow on other people.
Cocoa project
See: Cocoa, World Cocoa Foundation
1.0 Introduction
2.0 Where cocoa will grow
3.0 Parts of the cocoa tree
4.0 The leaf
5.0 The flower
6.0 Seed in the pod
7.0 Pollination and fertilization
8.0 Cocoa pod
9.0 Seeds
10.0 Making a seed bed
11.0 Choosing seeds and planting
12.0 Varieties of cocoa
13.0 Soils for cocoa
14.0 Prepare land for cocoa
15.0 Planting cocoa shade
16.0 Transplanting cocoa
17.0 Mulching and weeding cocoa
18.0 Pruning the cocoa tree
19.0 Fertilizers for cocoa
20.0 Harvesting pods
21.0 Fermenting
22.0 Drying, bagging and shipping
23.0 Pests and diseases
25.0 Returns, costs and profits
26.0 Commercial chocolate
27.0 Chocolate recipes
23.0 Pests and diseases
23.1.1 Cocoa capsid bugs, Helopeltis,Distantiella
23.1.2 Cocoa weevil borer, Pantorhytes
23.1.3 Amblypelta cocophaga
23.1.4 Termites
23.1.5 Longicorn beetles, Glenea lefebueri
23.1.6 Giant African snail, Achatina fulica
23.1.7 Rats
23.1.8 List of insect pests of Cocoa in Solomon Islands
23.1.9 Insect pests of cocoa in Papua New Guinea
23.1.10 Insect pest control methods
23.2.1 Black pod disease, Phytophthora palmivora
23.2.2 Bark Canker, Ceratocystis fimbriata
23.2.3 Dieback, vascular streak dieback virus
23.2.4 Pink disease, Botryobasidium salmonicolor
23.2.5 Thread blight, Corticium incisum
1.0 Introduction to the cocoa project
See diagram 55.1: Weeding the cocoa project
1. Cocoa is a cash crop. Cocoa growing can be profitable if the right kind of cocoa is grown, it is properly raised in a seed bed, it is planted properly under enough shade and in the right kind of soil, it is cared for properly as it grows including proper pruning, weeding, mulching, fertilizing and protection from diseases and pests, and it is harvested and processed properly. Cocoa is produced in tropical countries, but is processed and consumed in temperate countries.
2. Cocoa is an understorey species from on the equatorial slopes of the Andes Mountains in South America but is now cultivated widely. Two thirds of the world's production comes from West Africa and one third from Brazil and Dominican Republic. Cocoa has about 20 subspecies and cultivars are named according to the place where they were found or developed. The Criollo types have elongated, ridged, pointed fruits and white cotyledons. The Forastero types have with short, roundish, almost smooth fruits and purple cotyledons (2n = 20). It is classified in the plant family Sterculiaceae and has the botanical name "Theobroma cacao L". Some botanical names have "L" after them to show that they were named by the famous Swedish botanist Linnaeus (1707 - 1778). He believed that the ancient Aztecs of South America thought that the cocoa drink was a "drink of the gods", in Latin "theo broma". Mexicans named the pounded seeds "chocolate". Cocoa is now grown in many hot wetlands including the Pacific islands, but it needs a rich deep soil so this tree cannot be grown on the coral atolls.
3. The seeds of cocoa called cocoa "beans" are used to make chocolate. Fermented seeds are roasted, cracked and ground to give a powdery
mass. Fat is taken out to make cocoa. Cocoa has many uses including folk medicine. The seed contains energy, protein, fat, Ca, Mg, P, Fe, carotene, thiamine, riboflavin, niacin, and ascorbic acid. Chocolate is particularly high in phenylethylamine and contains more than 300 volatile compounds and theobromine, a stimulant related to caffeine (Theobromine does not contain bromine!). It contains some caffeine, in milligrams:
Cup: expresso coffee 310 mg, boiled coffee 100 mg, instant coffee 65 mg, tea 10 to 50 mg, cocoa 13 mg
Can: Coca Cola, 20 mg, Can (6 oz.) Pepsi Cola: 10 mg.
2.0 Where cocoa will grow
1. Cocoa needs rich, organic, well drained, moist, deep soils. Shallow soils are not suitable. It will not grow well on waterlogged soils, shallow stony soils, or soils with a hard stony layer near the surface. Also cocoa will not grow on coral soils, so it cannot be grown on atoll islands.
2. Cocoa trees do not like wind or drought and need high humidity and high rainfall, 1 250 to 3 000 mm per year. The rainfall must be well distributed and any dry period should be no longer than 3 months. Annual rainfall greater than 2 500 mm may result in a higher incidence of fungal
diseases. It requires annual temperature of 18.0oC to 28.5oC, with uniformly high temperatures mean of 26.6oC, diurnal temperature variation between 33.5oC and 18.0oC. It can be grown from 20 N to 20 S usually below 300 m above sea level. It must also have a high rainfall. It is very important also that the air should be moist or humid. Cocoa can live through a dry time with no rain if the soil it grows in holds water well, and the air is not too dry. If cocoa trees are grown among shade trees, these will help to keep the air moist.
3. Before they can be sold, the cocoa beans must be fermented in a special way. It is good if the cocoa is grown in a place close to a cocoa fermentary, so the beans can be processed. If this is not possible, the grower can make a small fermenting box.
4. Survey your locality are for cocoa growing. Is the local temperature hot enough? Is there enough rain in the local area? What is the rainfall in mm. per year? Is the air moist enough for cocoa? Is any cocoa grown in the district? Have they seen cocoa growing? Is a cocoa fermentary near the school? Can cocoa beans be taken to a ship for sending it to other countries? Is this is a good place for growing cocoa? Could you use any of the soils near the school? Can cocoa be grown near the school?
3.0 Parts of the cocoa tree
See diagram 55.3: Parts of the cocoa tree
1. The tree is 4 to 8 m tall. At 1 to 1.5 m the terminal bud breaks into 3 to 5 meristems to give upright shoots. It has spreading branches, stipules 5 to 14 mm long, large green leaves with petioles. The ovary has 5 carpels. The fruit is a drupe but is called a pod. The pod does not open, indehiscent, and stays on the tree. Pods vary in size and shape, being 10 to 32 cm long, spherical to cylindrical, pointed or blunt, smooth or warty, with or without 5 or 10 furrows, colour white or green or red, ripening to green or yellow or red or purple. The pod has 20 to 60 seeds arranged in 5 rows, variable in size, 2 to 4 cm long, ovoid or elliptic shape and 625 to 1 125 seeds per kg. The roots are mostly surface feeding with tap root penetrating to 2 m in friable soil
2. Go to where cocoa trees are growing. How high is the tree? Has it got a big canopy of leaves? Does the canopy of leaves have a mostly level base? Is the tree growing in a shady place? How much of the tree is in sunlight? How thick is the tree trunk at the base? Are there any water suckers called chupons growing from the trunk? The trunk branches into several of smaller branches called the fan. Go up close to the trunk and look for flowers. The clusters of flowers grow out from small cushions on the side of the trunk. Pick a large leaf. What colour is it? How long is it? What is its shape and size? After the flowers have formed, a small pod grows. The pod grows larger until it is ripe. Measure the length and width of a big pod. Open one pod to see the seeds, called "beans", inside. Estimate how much shade and full sun on the tree. Measure the thickness of the trunk and the height of the fan above the ground. Look very closely at a flower and describe it. Look at the places where the flowers grow out from the trunk at a small swelling called the cushion. Pick a leaf. Pick a ripe pod and open it to see inside.
4.0 The leaf
1. Observe the length and breadth of a leaf. Describe the shape of the leaf and the colour of the leaf. Young leaves may have a reddish or yellowish colour. The colour of leaves at the top of the tree is often different from colour of leaves growing low down on a tree. Note the difference between the colour of young and old leaves. Most cocoa leaves ends in a sharp point called the "drip tip". Measure the length and thickness of the leaf stalk, petiole. Note whether the leaves are held out sideways or hang down.
5.0 The flower
See diagram 55.5: Flowers
The flowers are formed in groups that grow out from small cushions on the main trunk and older branches that have no leaves. At first the flowers are small buds. Later they open. The opened flower has five long pink sepals joined at their bases, but the upper parts are long and pointed. The five yellowish petals have a most unusual shape. The base of the petal is very narrow. Then it widens to form a hollow sac like pouch. At the top of this part is a long narrow extension bent backwards and ends in a broad flattened tip. The male parts of the flower are in two groups. An outer row of five staminodes are sterile male parts that make no pollen. These long pointed staminodes point straight up out of the middle of the flower. An inner row of five stamens has an unusual shape. The stalk or filament that carries the anthers is bent over so that the male anthers are carried inside the hollow sac part of the five petals. The female parts of the flower consist of an ovary with five divisions. Each division or carpel has a long style or stalk, but the five styles are all joined at their base. At the top of the style five separate lobes, stigmas, receive the pollen.
1. Find the cushions from which the flowers grow.
2. Pick up a few flowers that fall off and do not develop.
3. Take off the 5 sepals.
4. Remove one petal.
5. Remove the five staminodes.
6. Look for the stamens. They are very small.
7. Look carefully on the ground under a tree and count the number of fallen flowers.
6.0 Seed in the pod
See diagram 55.6: Pod
Cocoa trees only start to bear fruit when they are 4 or 5 years old. Open a ripe fruit is by hitting it on the outside with a piece of stiff wood. Once a young fruit is 3 months old, it will usually stay on the tree and grow properly. It usually takes about 6 months for a fruit or pod to be ripe. The pod is ripe when the beans are loose and the pod will rattle when shaken.
When the fruit is opened, these are the parts that can be seen:
1. On the outside is the thick coat or husk. This coat may have deep grooves in it or shallow grooves. It may also have a lumpy surface with a warty appearance. It may be soft or hard and woody.
2. The large seeds or "beans" are in the centre of the pod. Each pod may have 20 to 60 seeds in it.
3. All around the seeds and between the seeds and the outside husk is a mass of white or pink soft pulp.
4. The pod has a strong stalk.
5. The pods may be up to one foot or 30 cm long and may be four inches or 10 cm wide.
6. The shape of the pods depends on the variety grown. Most cocoa trees are of the Forastero or Amelonado types, and these have short pods with a blunt end. The surface of the husk is not deeply grooved and is smooth, not warty. These pods are usually a yellow colour. Cocoa trees of the Criollo type are long and deeply grooved and form a point at the end. They are usually reddish in colour. Other shapes and colours of pods may be found in trees that are hybrids or crosses between different types of cocoa trees. The water shoots are called chupons. The flower has 5 sepals and 5 yellow petals. The long sterile male parts that make no pollen are called staminodes. The female ovary has 5 parts.
7.0 Pollination and fertilization
1. Flowers arise from cushions in the wood of the main stem and fan branches that is at least 2 to 3 years old. Only 1 to 5% of flowers are successfully pollinated and form pods. Pollinating insects are mainly tiny midges, e.g. Forcipomyia, and other small insects that require cool, dark, moist habitats and breed in rotting vegetation. When the male pollen is taken to the female stigmas by midges, the flower is pollinated. When the pollen grains grow down into the ovary, it will be fertilized. Only about one flower in 500 becomes a fruit. Many fertilized flowers drop off the tree. Even when a flower turns into a fruit, young fruits often shrivel up and drop off the tree when only 7 or 8 weeks old. A bad time or lack of plant food may cause this. Although only a few flowers are pollinated, the tree sets too many fruit to carry to maturity. Cocoa has a fruit thinning mechanism where the young fruit, called cherelles, stop growing, turn black and shrivel but do not fall off the tree. This is called cherelle wilt but it is not a disease, it is natural. The remaining pods take 5-6 months to ripen after pollination. Ripe pods also do not open by themselves or fall off the tree.
8.0 Cocoa pod
See diagram 55.6: Cocoa pod
1. There are many ways of telling if the pod is ripe. The beans will be loose inside a ripe pod and will rattle if you shake the pod. If the pod is ripe, the gum of the seeds will be slippery and it will taste sweet. If the gum around the seeds i, dry and if the seeds do not fail apart, the pod is not ripe.
2. Describe the outside of the pod. Is it grooved or smooth? Is the surface lumpy or warty? What colour is it? What type of cocoa is it likely to be?
3. Open the pod by hitting it with a strong stick. Use a sharp knife to cut cleanly across the wall of the pod and the soft pulp.
4. Scoop out all the seeds from the pod. Count the number of seeds.
5. All the seeds are joined to a long white part running down the centre of the pod.
9.0 Seeds
See diagram 55.9: Cocoa seed and its parts
Study some seeds and note the following:
1. Where the seed was broken off from the central white part, it leaves a small mark on the outside of the seed. This is very important because when a seed is planted this mark must be placed downwards in the seed bed or seed tin.
2. When the seed or "bean" is cut open the following parts can be seen:
2.1 The seed has a tough seed coat or testa.
2.2 The outer part of the seed coat is the soft pulp surrounding the seed.
2.3 The small plant or embryo (or "germ") is at one end of the seed.
2.4 The main part of the seed consists of the two seed leaves or "cotyledons" where the starchy food is stored.
2.5 A small mark on the outside of the seed coat shows it was once joined to the central white part of the pod.
3. Use a knife to cut the seed on the flat, not across them, then look for the embryo, small plant. Note the seed leaves, cotyledons, where the food is stored. Note the colour and thickness of the seed coat or testa.
4. The seeds are self-incompatible and are cross pollinated by midges. The pods contain up to 50 seeds surrounded by juicy sweet pulp. In nature the seeds are distributed by animals, usually monkeys. The seeds are rich in fat, called chocolate butter and contain alkaloids, e.g. theobromine giving them a bitter taste.
5. Germination occurs best in dim light. The seeds have limited viability and no dormancy. A tree bears pods at 4 or 5 years. A pod has 20 to 60 seeds (beans). The average pod is 30 cm long. Amelonado or Forastero varieties have short pods with no pointed ends. Criollo cocoas have yellow or red pods, with rough surface and deep grooves. Amelonado cocoa pod is smoother and rounder and the seeds have dark purple seed leaves. Trinitario pods have many shapes. A pod takes 6 months to be fully grown and ripe? Plant a cocoa seed with the small mark downwards. The small plant inside a bean is the embryo. The outside coat of a seed is the testa. A Criollo pod is red or yellow. An Amelonado pod is yellow.
10.0 Making a seed bed
See diagram 55.10: Seed bed for cocoa
1. The seedlings must have shade so build a small roofed shelter over the place where you will plant the seeds.
2. The seedlings need good soil. Get some good dark soil and break up the lumps until it is fine and loose. Then mix a little manure with it. Spread this soil over the soil in the seed bed area, and place the seeds into it. Also, you can put the soil into jam tins or pieces of bamboo or plastic bags with holes in them near the bottom.
3. Keep the seedlings wet. They must be watered every day.
4. Do not allow weeds to grow near the seedlings. If insects come to eat the leaves of the seedlings, they must be killed.
11.0 Choosing seeds and planting
See diagram: 55.10 Nursery | See diagram 55.11: Right and wrong ways of harvesting pods
1. Propagation may be by cuttings, buddings or graftings, but seeding is cheaper. Seeds germinate at maturity, and are viable only a short time. They may be stored 10 to 13 weeks if moisture content is kept at 50%. Soon after picking, pulp is removed from seeds that are then planted in shaded nursery beds or baskets. Collect seed from ripe pods and plant immediately. At least 90% should germinate within 2 weeks. Hybrid seeds are available but the plants can be highly variable in growth and performance Planting of seed direct to the field is not practised due to lack of irrigation and problems with weed and pest management.
2. Choose a pod of the right variety from a high bearing tree. Chose only an Amelonado pod of large size from a high bearing tree.
3. The pod must be ripe and healthy. A ripe pod will have loose seeds inside when shook. Use a knife to cut off the pod leaving some stalk on the tree. Never pull the pod from the tree because you may pull off the cushion and then it cannot make any more flowers.
4. Select only the best seeds for planting. Open the ripe pod by hitting it with a stick. Do not use a knife because it might cut the seeds. Discard the small seeds at each end of the pod. Use only the big seeds in the middle of the pod used for planting.
5. Sow the large seeds soon after they are taken from the pod. Do not keep the pod for more than a week because the embryo will die.
6. Hold the seeds by the flat sides and with the small scar pointing downwards. Push the seed down into the moist soil until it is just covered. Do not push the seed in too deeply or it will not grow well.
7. If the seeds are planted in the soil and not in tins, plant them in rows 25 cm apart. Leave a space of 25 cm between the seeds in a row.
8. Water the seeds after planting.
12.0 Kinds of Cocoa
See diagram 55.12: Three groups of cocoa varieties: Criollo, Forastero Trinitario
1. Plant only the best varieties of cocoa. Most of the common cocoa varieties cross or breed with one another so there are many cocoa varieties. The two main groups of cocoa varieties are the Criollo and Forastero cocoas.
2. The Criollo cocoas have yellow or red ripe pods and the pods have deep grooves on the outside and the surface of the pods is rough or warty. The ends of the pods are pointed. The seeds or beans are large and rounded with white or pale violet seed leaves. These cocoas have a much better taste than other cocoas, but are not common.
3. Forastero cocoas are the most common. The pods are not as deeply grooved as the Criollo cocoas and may even be smooth. The ripe pods are green or yellow, and the wall of the pod is very thick and woody. The pods are also shorter and more rounded. The two groups of Forastero cocoas are the Amelonado cocoas with yellow pods with flat seeds that have deep purple seed leaves inside and the Trinitario cocoas, probably crosses between Criollo and Forastero cocoas because the pods look like Criollo and Forastero types.
4. The best varieties to grow are the Amelonado cocoas because they are hardy, more vigorous, and yield well.
13.0 Soils for Cocoa
See diagram 55.13: A good soil and 3 bad soils for cocoa
1. Cocoa is grown on a wide range of soil types but soils with moderate to high fertility are favoured since fertilizer inputs under traditional production systems are low. The best soils for cocoa are soft loose deep soils with good structure, e.g. clay loam. Soils. The main needs are a free draining soil with good moisture holding capacity and pH range from 4.5 to 7.0 preferably close to 6.5.
2. The soil should be at least 1.5 metres deep. Shallow soils do not give cocoa enough root room. If the soil has been dug often to a certain level, the soil under where they have been digging will be hard and form a soil pan. This will restrict the roots of cocoa and cause a swampy soil with the water repeated digging to the same level just below the surface. If the water table is close to the surface the roots have no room to grow in this soil, the trees have no "root room".
3. Dig a hole in a place where cocoa is growing to see if it is loose and deep
14.0 Prepare cocoa land
See diagram 55.13: Plan of a small plantation for 40 cocoa trees | See 6.9.14: Composting
1. Choose a suitable piece of land. The soil must be good enough for cocoas. The area must be big enough for the school project.
2. Prepare the land to be ready for planting the seedlings.
If about 60 cocoa seeds or beans are planted at least 50 will germinate and grow. Discard the 10 weakest seedlings leaving 40 cocoa seedlings. Plant the cocoa seedlings 3 m apart each way. So the piece of land must be 15 metres wide and 18 metres long. Put stakes in the soil at each planting place.
3. Clear the land by cutting down grass and bushes and leaving them on the soil to keep the soil moist.
4. Provide some shade for the young cocoa seedlings with coconuts about 9 m feet apart or shade trees, e.g. Leucaena (Lusina). They are fast growing legumes that put nitrogen into the soil and giving shade
15.0 Planting cocoa shade
See diagram 55.15: Planting cocoa and Ikofala ants nests made out of leaves
1. Shade may be remnant forest, interplanting with species that provide a commercial return, e.g. bananas or coconuts or shade trees selected on basis of amount of nitrogen fixed if a legume, fuel wood produced, suppresses weeds, and grows well with cocoa. Shade trees include species of Albizia, Erythrina, Gliricida, Inga, Leucaena, Musanga, and Peltophorum. Ask an officer of the Department of Agriculture to recommend supply of shade trees.
2. Dig trenches one metre long in between the cocoa, or plant Leucaena seeds in strips or one metre long between cocoa planting places. Mark out strips of soil one metre long between the stakes where cocoa seedlings will be planted.
3. Into each of these strips spread about 20 Leucaena seeds and cover them up with 3 cm soil. Weed the strip each week. When about 1.3 m high, pull out the smaller shade plants leaving the 3. biggest at each strip. When the shade trees are 2 m high, the cocoa seedlings can be planted.
4. Look in small trees for Ikofala ants nests made houses out of leaves. These ants help to keep pests away from cocoa. Put wooden stakes at each of the 40 planting positions.
5. Cocoa grows well if it has part shade at first but as the tree grows, some shade trees are removed. Seedling cacao does best with only 25% full sunlight, saplings with closer to 50%. Cut the stem of Leucaena shade trees just below the soil surface. Cocoa can be grown without any shade, but the trees do not grow well and much fertilizer must be used. Shade removal is possible after 3 to 4 years but in many situations windbreaks will be beneficial or necessary.
16.0 Transplanting cocoa
See diagram 55.16: Dig a hole for cocoa a month before planting
1. Transplant 3 to 6 months after planting when about 0.6 m tall into shaded fields at 2.4 m x 2.4 m or 3.6 m x 3.6 m. Use stakes to mark the positions where the cocoa will be planted. Planting density may range from 800 to 3 000 trees / ha with about 1 200 trees / ha common in under permanent shade.
2. One month before planting, dig a hole 30 cm wide and 45 cm deep. Keep the dug out topsoil separate from the subsoil.
3. Just before planting, replace the subsoil in the bottom of the hole and replace the topsoil for the planting of the seedlings.
4. When the seedlings are about six months old, take them out of the nursery seed beds or gradually take away the shade cover so that the seedlings get used to the sun. Discard weak seedlings. They should not be used for planting.
5. Transplant the cocoa seedlings during the start of the wet season or at a time of rain.
6. Use a spade to dig up seedlings from the seed beds and keep a ball of earth around the roots. If the seedlings were raised in tins or pots or bags, remove carefully to keep the earth around the roots. Turn the seedling in a tin upside down and tap the edge of the sharply on something hard.
7. Plant the seedlings into a hole in the topsoil then put soil around the seedling level with the soil surface. Then water the seedling.
17.0 Mulching and weeding cocoa
See diagram 55.17: Mulch
1. A mulch is any light loose covering laid on the surface of the soil. The commonest mulch is made of dead weeds, but any kind of plant rubbish can be used.
A mulch helps plants on the following ways:
1. helps to keep the surface of the soil moist and cool. In cold weather it keeps the soil warm,
2. protects the soil and stops heavy rain washing away the topsoil,
3. helps to keep sun off the weeds and stops their growing,
4. keeps the surface of the topsoil soft and moist,
5. contains some nutrients, plant foods, which can be washed down into the soil.
However, in a dry climate with only occasional light rain, too much mulch may absorb all the rainfall so that no moisture reaches the plant roots.
2. To make a mulch, clear a one metre circle around each cocoa seedling then cover the ground with mulch 10 cm thick. Leave a small clear space of the bare soil around the seedlings so that the mulch does not touch the seedling. The clear space helps to stop the attack of pests. As the tree grows bigger, widen the area covered by mulch until all the soil is covered. Do not use pieces of wood or sticks as mulch because they take too long to rot down.
Weed 3 to 4 times in the year during the establishment phase before the canopy closes by manual slashing along the tree rows or around young plants. Also, use herbicides, e.g. "Gramoxone" and "Roundup". For the efficient application of herbicides, plant the cocoa trees in lines. When cocoa is mature and a complete canopy is formed, heavy shading and leaf mulch inhibit weed growth so only a few woody weeds must be removed. However, breaks in the canopy or equipment access paths allow weeds to grow again.
18.0 Pruning the cocoa tree
See diagram 55.18: Pruning
1. As the cocoa seedling grows it has to be pruned so it will grow into the right shape for cocoa and to limit tree height for easy harvesting. The young tree forms a straight main stem about 1 to 1.5 metres high. It then branches into 3 to 5 main fan branches, called the first jorquette. The tree then makes two kinds of branches: 1. Fan branches with leaves growing flat along both sides of the stem. 2. Sucker branches called chupons with leaves growing all the way around the stem.
2. When the first fan branches have formed then chupon branches will grow. If chupons are left on the tree, it will grow into a bad shape with two or three fans, one above the other. So cut off all the chupons as soon as they are seen to prevent subsequent jorquettes and restrict further vertical growth. 3. Also prune fan branches to maintain evenness in the structure, dead or diseased branches or any branches that hang down low. Otherwise, never prune fan branches. Remove floral buds until trees are 5 years old.
4. Use a sharp knife, secateurs or pruning saw and cut close to the main stem to prevent the chupons growing again. If the pruning cut is large, paint it over with tar or creosote or another chemical to kill fungi. Apparently pruning itself does not promote high yields.
19.0 Fertilizing cocoa
See diagram 55.19: Drip circle for cocoa
About 200 kg N, 25 kg P, 300 kg K, and 140 kg Ca are needed per ha to grow the trees before pod production. For each 1 000 kg of dry beans harvested, about 20 kg N, 4 kg P, and 10 kg K are removed if the pod husks are also removed from the field, the K removed increases to about 50 kg. You can use soil and leaf analyses to find the nutritional needs of cocoa. Leaf analyses are not accurate due to the difficulty in sampling leaves of the same age and the influence of shading on the nutrient composition of leaves. Some experts can use visual symptoms of mineral deficiencies to recommend use of fertilizers.
Ask an agriculture officer which fertilizers should be used.
Some common fertilizers:
Urea: This has much nitrogen in it (46%) but it makes the soil a bit sour (acid) and some nitrogen may be lost into the air
Sulfate of ammonia: This has nitrogen (21%) and sulfur (24%) in it. Do not use this on an acid soil because it makes the soil more acid.
Calcium ammonium nitrate: This has 20% of nitrogen in it, but it also has calcium. Use it on acid soils.
Superphosphate has phosphorus nutrient in it, but it also has calcium and sulfur.
Triple superphosphate has much more phosphorus in it, but it is much more expensive to buy.
Muriate of potash contains 60% potassium oxide but is expensive.
Sulfate of potash contains potassium and sulfur.
Limestone or lime is only used when soils are very acid and do not have enough calcium.
Magnesium sulfate contains magnesium and sulfur.
Trace element fertilizers give the soil very small amounts of some elements. Some of these fertilizers give the soil iron, or copper, or manganese, or molybdenum.
If a soil needs just one plant food, use a single fertilizer. However you can mix single fertilizers for several nutrients.
1. When applying fertilizers, first take away all weeds growing near the trees. If a mulch has been used, rake this away and leave the soil bare.
2. Sprinkle the fertilizer evenly in a wide ring around the tree, but do not put any of it close to the tree trunk. Sprinkle fertilizer right out as far as drips of rain fall down from the leaves. This is called the drip circle.
3. Rake the mulch back on top of the fertilizer. Leave a clear space close to the base of the tree.
20.0 Harvesting pods
See diagram 55.11: Harvesting
1. The cocoa harvest can be spread over several months. Although pods may be available for harvest throughout the year usually one or two peak harvest periods are used depending on flowering in response to rainfall.
2. Ripe pods turn from green or deep red to yellow or orange. Only the ripe pods are harvested but they can be left on the tree for 2 to 3 weeks. Also, under ripe pods can be fermented. Pod left too long on the tree will rot and the beans may germinate inside the pod.
3. Harvesting is by hand using machetes or knives to cut pods from the tree. Pulling the pods from the tree can damage the flower cushion and tear the bark.
After harvest, the pods are opened and the beans scooped out by hand. This can be done immediately or delayed for a few days. The plant placenta joining the beans inside the pod should be separated from the wet beans before fermentation.
4. After about two years trees will start to make flowers and fruit. Although fruits mature throughout the year, usually only two harvests are made, e.g. in the Pacific islands the ripe pods should be harvested every two weeks between April and September and every four weeks from September to March. From fertilization to harvesting the fruit requires 5 to 6 months. Harvest season lasts about 5 months. Cut the pods from trees and store on the ground. Crack the pods and remove the beans. Burn the husks. Production varies from 29 kg / ha to 2,000 kg / ha, 0.5 to 10 kg / tree.
21.0 Fermenting
See diagram: 55.21 Fermenting
1. Fermentation develops chocolate flavour that develops further during roasting of the beans. Also, fermentation allows easy extraction of beans from the pod. The wet beans are taken out of the pods then heaped to allow them to increase temperature due to exothermic chemical reactions in the pulp caused by the fermentation micro-organisms. At first the sticky mucilage around the beans breaks down drains off as "sweatings". After 36 to 72 hours the beans are killed by the heat and chemical changes occur inside the bean and will continue during drying. During fermentation the beans become darker and wrinkled and lose their bitter taste. The beans are collected, heaped, covered with leaves and allowed to ferment through the action of microbes and enzymes naturally present This process kills the germ of the bean, removes adhering pulp and modifies the flavour and colour (now brown). After drying, the beans are ready for export.
2. Fermentation can be done wooden boxes about 800 kg capacity covered by banana leaves. Usually at least 90 kg of beans are needed for processing for 5 to 7 days, depending on the type of cocoa being grown and design of the fermenting box. The percentage of dry fermented beans to wet unfermented beans is called "recovery". It ranges from about 40% for under ripe pods to 45% for over-ripe pods.
3. Make a fermenting box with some holes in it so air can get in.
4. Ferment the beans 2 to 8 days before drying in sun. Mix the beans every 2 days.
5. Test some beans to see if they are properly fermented. Before fermenting the kernels inside are purple, but after fermenting they are reddish brown.
22.0 Drying, bagging and shipping
1. Fermented beans are dried in the sun or artificially to a 6 to 7% moisture content dry basis. Artificial drying can cause beans to be very
acidic if they are dried too quickly. Dried beans are hand sorted or mechanically sieved and winnowed to remove defective beans and debris.
The number of pods required to produce 1 kg of dried beans is called the "pod index". Low pod index means good bean size and a high weight of beans per pod.
2. After fermenting the cocoa beans must be dried. Building a good drier is quite hard, so try to find a drier that the school could use. The beans must be well dried and have only 6% moisture. In most dryers heat comes from a wood fire, but the beans must not be heated over 50oC and they must be stirred while they are being dried. The beans are then bagged and shipped. Further processing includes roasting, crushing, and separating out the kernel, grinding the nibs and extraction of about half of the fat.
3. Quality of cocoa beans depends on flavour attributes, average bean weight 1.0 to 1.2 g, bean count of 100 to 83 beans per 100 g, low shell percentage of 11 to 17%, and fat content of the cotyledons (nib) at least 53%.
4. In many countries cocoa fermentaries and cocoa dealers and buyers are licensed to ensure production is at the standards of export cocoa. Inspectors of cocoa beans intended for export control quality of cocoa beans. The term "cacao bean" means the seed of the cacao trees (Theobroma cacao L) which has not been passed through a fermentation and drying process. The term "cocoa bean" means a whole cacao bean that has been fermented and dried.
The term "cocoa processing" means the process of fermenting and drying cacao beans for converting cacao beans into cocoa beans.
The term "fermentary" means any place or premises maintained for cocoa processing. The term "dry cocoa" means cocoa beans that have been evenly dried and the moisture content of which is not more than 8% and not more than 1000 beans per kilogram. The term "defective bean" means a cocoa bean that is either insect or mite damaged or germinated (shell has been pierced by the seed germ) or flat (too thin) or coupled (beans stuck together). The standard for "Export Cocoa" is based on accepted international standards and is prescribed by local legislation. Cocoa inspectors put inspection marks on cocoa bags for export. They can check samples taken through the meshes of the bags by using a stab sampler.
5. In countries exporting cocoa beans, particularly in West Africa, desiccant bags are placed inside the shipping containers with the cocoa beans. Addition of the desiccant bags inside the containers significantly reduces the amount of condensation during the transit period. The end result is a marked improvement of the quality of the cocoa beans.
23.0 Pests and diseases
Cocoa is grown in places that are hot, moist and partly shaded that allow many fungus diseases and pests to live. Regularly examine the cocoa trees for signs of diseases and pests and then get advice from the Department of Agriculture on how to control them. The normally recommended methods for the control of capsids and black pod disease that involve mainly the use of conventional insecticides and fungicides are now considered by many to be environmentally unfriendly, posing a threat to both humans and non-target insects, e.g. the midges that pollinate the cocoa flowers. Some cocoa pests that occur in PNG that do not occur in Bougainville or the Solomon Islands.
You can find much information about pests and diseases from the internet at websites run by Integrated Pest Management (IPM)
23.1.1 Cocoa capsid bugs (Hemiptera, sub-order Heteroptera, Family Miridae) mirids, e.g. Helopeltis sp., Distantiella sp.
See diagram 55.23.1.1: Capsid bugs
Capsids (Helopeltis or Distantiella) have not been recorded in the Solomon Islands and they are not in Bougainville.
1. Capsids are sucking insects that feed mainly on the husk of cocoa pods and young shoots of chupons and fans. They use their piercing mouth parts to suck up sap. Their feeding results in dark markings called lesions on pods, shoots, petioles, leaf midrib and black angular spots on the leaf surface caused by their toxic saliva. Secondary damage of canker and dieback occurs when the lesions are invaded by parasitic fungi, e.g. Calonectria and Fusarium species. In very serious infection the entire tree looks burnt.
2. Capsids may occur at a break in the cocoa shade canopy followed by growth of vegetative chupons. Feeding on fan branches results in damage to the tree canopy that causes more damage to exposed cocoa in the dry season, called "capsid blast".
3. The female adults lay eggs in the outer layer of pods and beneath the bark of young shoots then go through five nymph stages for a total incubation period of 2-17 days. The adults are about 5.5 cm long. The nymphs, are smaller and have no wings.
4. They can be controlled by spraying the plants with an insecticide, e.g. "Gammalin 20" (Lindane) followed by a second spray time to kill the bugs from eggs that were not killed by the first spraying. However, the adverse side effects of persistent chemicals, including the destruction of non-target beneficial insects, e.g. midges, and their long lasting residual effects in the environment, make them undesirable so some scientists want to replace Lindane. Pesticide can be applied to mature cocoa with motorized knapsack mist blowers.
23.1.2 Cocoa weevil borer (Pantorhytes)
Pantorhytes biplagiatus (P. plutus) is damaging in the Solomon Islands. This is probably the worst of all insect pests on cocoa. This pest occurs in Papua New Guinea and in the Solomon Islands. The adult weevils lay their eggs in small cracks in the bark of the cocoa tree. The small grubs that come out of the eggs bore holes into the trunk as they grow. Some jelly like liquid comes out of these holes. The grubs make holes right through the trunk and may go around and ring bark the branch or trunk. It is not much good trying to kill these insects with chemicals. Collect the adult beetles by hand and kill them. Get some Ikofala or "crazy ants" to come into the cocoa trees. These ants make their nests in soursop trees, so planting some of these trees will help to bring the ants into the cocoa. The ants drive away the weevils. 3. The Pipturus plant attracts the cocoa weevils. Ask the agricultural officer to show you these plants so you can destroy them.
23.1.3 Amblypelta cocophaga
It is a minor pest but can be controlled with crazy ants. They are brown or green bugs about 2 cm long. They have very long feelers, but in the young bugs the feelers are thick. The young and old bugs feed on cocoa pods and young shoots. They suck juices up through long thin feeding tubes. If they feed on young pods, the whole pod may be spoiled, and young shoots may be killed. These bugs also attack coconut trees and make the young nuts fall of the tree. Spray the pods with the same spray used to kill capsids. Get some ikofala ants into the cocoa trees by planting sour-sop trees among the cocoa trees.
23.1.4 Termites
See diagram 55.23.1.4: Termites
No termites are listed as pests by CABI. Termites or "white ants" are ants that live by eating holes in wood. They may weaken a branch or a trunk so much that it falls over. It is often hard to tell whether the termites are in a tree because they make holes just under the bark and there may be no signs outside.
Treatment may include the following:
1. If an attack is found, the branch can be cut off close to the main branch.
2. If a nest is found, it can be opened a little and a bottle full of weak chlordane (0.2%) mixture poured into it.
3. Slowly pour "Dursban" (Chlorpyrifos) solution at the base of each transplanted seedling.
23.1.5 Longicorn beetles (long antennas beetles), e.g. Glenea lefebueri
See diagram 55.23.1.4: Longicorn beetles
The longicorn beetle (Family Cerambycidae) Glenea aluensis occurs in the Solomon Islands, although neither G. aluensis or G. lefebueri are listed by CABI. They are associated with poorly managed cocoa under heavy shade or near forests. Be sure that they are economically important before any control because control is very difficult. These pests are big beetles with long feelers. The beetles are either bright yellow or bright blue. The grubs of these beetles are pale yellow in colour and have strong jaws. The beetles lay their eggs on the trunk. The grubs hatch out and eat holes in the soft part of the trunk. The trunk may be ring barked and die. Signs of this grub may be seen as lumps of wood chips stuck together in rusty coloured lumps. These are pushed out and breathing holes made by the grubs. The fungus causing the tree canker may get into the tree through these holes. The way to kill these grubs is to open some holes and pour in an insecticide. This can be made up by mixing together: 12 litre of Lebaycid, 4 litres of white oil, 12 litres of water 16 mL wetting agent.
23.1.6 Giant African Snail (GAS) (Achatina fulica)
1. The snail can kill young cocoa seedlings and damage cocoa trees. It can feed on leaves and tubers of many types of crops.
2. It searches for food at night and hides in the soil during daytime. The eggs are 5 mm diameter, round and white are usually found in batches of about 200 eggs just beneath the soil surface. The eggs hatch within 15 days after laying.
3. It was introduced from East Africa and is now established in some Pacific islands but not been reported from Cook Islands, Fiji, Kiribati, Nauru, Niue, Pitcairn Island, Solomon Islands, Tokelau and Tonga. It can be easily transported between countries in containers, machinery and empty bottles. After it has become established, it is extremely difficult to eradicate. Villagers should collect the snails and kill them by burning or immersing in sea water. Clear rubbish and weeds in infested areas to reduce breeding places. Do not bring planting materials from infested areas to places where the snail is not present.
4. The best way to control Giant African Snail is to eat them. The snail can be controlled with chemical baits, e.g. Blitzem, Esbit, Canned Heat (metaldehyde) fuel tablets and snail bait, mixed with sawdust and cement. However, but baits may be dangerous if eaten by children or domestic animals.
See: Metaldehyde
23.1.7 Rats
See diagram 55.23.1.7: Poison baits for rats
Rats may do much damage to cocoa pods, because they eat holes in the outside of the pods so they can eat the soft part inside. A good way to stop rats is to put wax blocks containing brodifacoum into bamboo tubes and tie these on to the branches of the tree. Another thing to do is to get some crazy ants or ikofala ants into the cocoa area. These ants keep the rats away. Whatever you do to control rodents it is essential that measures are carried out on an area wide basis, one farmer trying to control rats is useless.
23.1.8 List of insect pests of Cocoa in Solomon Islands
from CABI Crop Protection Compendium CD
Achatina fulica (giant African land snail)
Ahasverus advena (foreign grain beetle)
Amblypelta cocophaga (coconut bug)
Aphis craccivora (groundnut aphid)
Aphis gossypii (cotton aphid)
Aspidiotus destructor (coconut scale)
Brevipalpus phoenicis (false spider mite)
Carpophilus
Ceroplastes destructor (white wax scale)
Corcyra cephalonica (rice meal moth)
Dysmicoccus brevipes (pineapple mealy bug)
Euwallacea fornicatus (tea shot hole borer)
Ferrisia virgata (striped mealy bug)
Homona coffearia (tea tortrix)
Leptoglossus gonagra (squash bug)
Nezara viridula (green stink bug)
Pantorhytes (weevil borers)
Planococcus minor (passionvine, mealy bug)
Rhynchophorus bilineatus (black palm weevil)
Selenothrips rubrocinctus (red banded thrips)
Spodoptera litura (taro caterpillar)
Tenebroides mauritanicus (cadelle)
Toxoptera aurantii (camellia aphid)
23.1.9 Insect pests of cocoa in Papua New Guinea, importance and control
J. E. Moxon, Department of Agriculture and Livestock, Papua New Guinea
Many insects feed on cocoa, attacking most parts of the tree in both the establishment and production phases. Crop losses range from most serious to slight depending on insect type, density, distribution, occurrence and duration of attack. Many serious pests are absent from the North Solomons Province, Papua New Guinea, which produces about half of the country's cocoa.
An integrated approach to control is preferred because of a wide variety of pests and their natural enemy complexes. Both large estate and smallholder sectors produce large amounts of cocoa though their farming methods are generally very different, the former having a much higher technical, financial and management input than the latter. It is often necessary to provide different pest control recommendations to suit the two farming sectors.
Many smallholder blocks either begin as or, more usually, become mixed gardens containing coconuts, areca palms, bananas and fruits, nuts and food crops. Some pest associations between these crops and cocoa in the farming system and between shade trees and cocoa are considered and the value of coconut as a shade for cocoa is highlighted.
Cocoa is the most important cash crop in the lowland areas and large scale redevelopment of over mature cocoa and development in new regions using high yielding Trinitario x Upper Amazon hybrid material is expected to increase production significantly over the next few years. Many factors, e.g. climate, soils and marketing, favour cocoa production in the major cocoa growing regions, but pests, diseases and poor management can impose serious constraints. Pantorhytes weevils, caterpillars and vascular streak dieback can cause the collapse of the industry in a major regions. Over 300 species of pests have been associated with cocoa in Papua New Guinea). However, only about 10 pests regularly cause widespread, economic damage. Damaging Pantorhytes weevil species, mirids, and some other pests for example are believed to be absent from North Solomons Province, Papua New Guinea, an island that produces half of the country's cocoa.
Main insect pests of cocoa in order of economic importance
Group 1 (the worst pests)
Wood boring Pantorhytes beetle larva (Coleoptera: Curculionidae) Larvae bore into wood of trunk and main branches
Leaf eating caterpillars (Lepidoptera: Limacodidae) (Lepidoptera: Noctuidae) (Lepidoptera: Geometridae) Larvae eat both young and mature leaves
Wood boring longicorn beetles (Coleoptera: Cerambycidae) Larvae bore into wood of trunk and main branches
Pod damaging mirids (Hemiptera: Miridae) Adults and nymphs suck sap from pods and shoots
Group 2
Shoot chewing Grey weevils (Coleoptera: Curculionidae) Adults chew bark on shoots of young cocoa
Terminal branch feeding Pansepta moths (Lepidoptera: Xylorictidae) Grubs bore in branches
Wood eating termites (Isoptera: Kalotennitidae) Adults and nymphs chew wood inside the tree
Group 3
Pod sucking bug Amblypelta (Hemiptera: Coreidae) Adults and nymphs suck sap from pods
Root chewing Chafer beetles (Coleoptera: Melolonthinae) Larvae chew roots of young trees
Mealy bugs (Hemiptera: Pseudococcidae) Adults and nymphs suck sap from shoots, pods an flowers
Tip boring Oxymagis (Coleoptera: Cerambycidae) Larvae bore into terminal branches
Pod Borers (Lepidoptera: Tortricidae) (Lepidoptera: Olethreutidae) Larvae bore into husk of pods
Leaf eating Rhyparids (Coleoptera: Chrysomelidae) Adults eat leaves
Stem boring Zeuzera moths (Lepidoptera: Cossidae) Larvae bore into wood of trunk and main branches
The economic importance of an insect is ultimately measured in terms of crop loss. This can be a direct result of feeding on pods or indirect result of feeding damage on other parts of the tree. The major pests in Papua New Guinea attack many parts of the tree including pods, leaves, shoots, branches, trunks and roots. Both young and mature cocoa are attacked and so pest control is often necessary throughout the life of the crop. Pests which damage young cocoa may either stunt or kill the tree necessitating replanting or retard growth all of which reduce time to bearing and thus result in a measurable crop loss. Pests which attack the wood of mature trees can cause senility or death and so are particularly important. The insect type, density, distribution, occurrence and duration of attack contribute to the overall importance of a pest.
Pantorhytes
Pantorhytes species are now possibly the worst pest of cocoa in Papua New Guinea. Pantorhytes species occur in New Guinea, the Bismarck Archipelago and the Solomon Islands, with species extending to Queensland in Australia. In the North Solomons Province, Papua New Guinea, which produces half the country's cocoa, P. biplagiatus is scarce and never of economic importance while the same species in the neighbouring Solomon Islands can be most damaging. Pantorhytes species are robust, heavily sclerotised, wingless weevils about 1-5 cm long. The eggs which are white, ovoid and about 2 mm long, are laid singly in crevices on the trunk and main branches, particularly near the jorquette, intersection of main branches and tree base. Eggs hatch after 2 to 3 weeks. The larva has a well developed brown head and curved cream body with rows of fine hairs. The larva bores into the wood 1 to 2 cm deep and feeds on sap wood making tunnels or channels parallel to the surface. The larva feeds for 3 to 9 months through 9 instars and then pupates beneath the bark in about 14 days. The newly emerged adults feed for 4 to 6 weeks before mating, after which time the female lays about 2 eggs per day sometimes through out her life span of one to two years. Adults feed mainly on the semihardened bark of young cocoa shoots and occasionally on pod husks, leaves and flowers though damage is rarely economic. Larval feeding, by contrast, is usually devastating. The larvae bore into the sapwood of trunks and main branches of trees more than about two and a half years old, causing structural weak ness, tip dieback and a general canopy degradation, branches may be ring barked and die and trees may split at the jorquette. A severe drop in production follows and often a large proportion of the plantation dies.
Wounds made by larvae in the bark are an entry point for bark canker, Phytophthora pabnivora, which also reduces yield and kills trees. Termites may also enter the tree as secondary pests.
Pansepta
Pansepta larvae are most damaging on young trees when they bore into or ring bark the main branches. However, since about the beginning of 1987 Pansepta has been particularly abundant in New Britain and large areas are suffering from severe tip dieback, including main branches, canopy degradation and crop loss. The pest is easily controlled on young trees by removing the web and applying dimethoate, a systemic insecticide, onto the bark with a brush or swab but there is no economic control recommendation for Pansepta on mature trees. Pansepta is usually only a problem on lightly shaded cocoa although since 1987 the pest has been reported throughout well shaded plantings.
Termites
Several species of termite attack cocoa in Papua New Guinea. The most important species is the giant termite, Neotermes papuana that occurs throughout the islands region and is particularly damaging in New Britain, Papua New Guinea. Termites first enter the tree via dead branches and then make their nest in the living wood and feed it. The tree canopy is reduced, production falls, branches die and eventually the tree is killed. Termites are easily controlled by exposing part of the nest and pouring a dilute solution of insecticide into it. The newer pyrethroids give a good kill and are safe to use. Neotermes papuana does not construct covered runways on the tree but the location of the nest is indicated by a water soaked appearance on the bark. Some shade trees are also attacked by termites and so these must also be inspected regularly and treated. Termite infestations can be prevented to some extent by pruning dead branches from the tree.
Amblypelta
A number of species have been noted feeding on cocoa but only Amblypelta theobromae and Amblypelta cocophaga are pests. Amblypelta theobromae can cause large crop losses on mainland Papua New Guinea. Adults and nymphs suck the sap from pods and shoots causing damage similar to mirids. The life cycle takes about 6 weeks. A. cocophaga occurs in the North Solomons and Solomon Islands where it is an occasional pest of cocoa. The ant Oecophylla smaragdina is negatively associated with both species. Amplypelta is controlled in the same way as mirids
Rhyparida
Chrysomelid beetles of the genus Rhyparida which feed on the flush leaves of cocoa can build up rapidly and cause extensive defoliation. There are many species of Rhyparida distributed throughout Papua New Guinea. Eggs are laid on the ground and the larvae feed on plant roots. Pupation also occurs in the ground and the life cycle takes about 6 weeks. Defoliation can be prolonged and particularly damaging when associated with dry weather. It is often necessary therefore to control Rhyparida on cocoa trees up to about 2 years old using insecticides.
Pod borers
Two pod boring moths, Cryptophlebia encarpa and Olethreutes sp. are minor pests of cocoa in Papua New Guinea and the Solomon Islands. Eggs are laid singly on the pod surface. The larvae hatch within 24 hours and burrow into the epicarp of the pod husk to feed. The larvae feed for 13 to 15 days.
23.1.10 Insect pest control methods
1. Biological control using crazy ants
Although over 30 parasites predators and pathogenic fungi have been recorded from Pantorhytes none have shown promise as biocontrol as the crazy ant, Anoplolepsis longipes and possibly Oecophylla smaragdina. Dense crazy ant populations eliminate Pantorhytes from cocoa but as the ant density decreases so the Pantorhytes reinvade and increase. A technique has been developed for collecting and introducing crazy ants to cocoa. The crazy ant also controls some other cocoa pests. Present work is attempting to develop methods of stabilizing crazy ant populations which are sometimes transient.
2. Hand-picking of adults
Adults weevils are easily seen, collected and destroyed by hand during the middle of the day when they descend through the canopy to cooler places. This method is popular with smallholders who operate on restricted budget and some large estates also find the method cost effective when operating on a "bounty payment system.
3. Larval channel paints
Larvae are easily detected in the tree by the presence of frass expelled from the entrance hold of the larval channel. The frass is removed with a stiff brush and the larvae are then easily killed by applying a solution (channel paint) of Dichlorvos, White Oil, Ridomil and water with a small 2 cm brush onto the bark around the entrance hole. About 80% of larvae treated in this way die. Ridomil is added to the channel paint to control any Phytophthora that might be present. It is recommended that trees severely infested with Pantorhytes larvae be inspected and treated at least every two weeks.
4. Coconut shade
Pantorhytes populations are often, but not always, low in cocoa grown beneath coconut shade although the reason for this is unknown. One possible explanation is that coconuts often harbour Oecophylla smaragdina ants which are believed to repel Pantorhytes By contrast, cocoa grown beneath other shades such as Leucaena and Gliricidia is often badly damaged by Pantorhytes. For this reason and other considerations it is strongly recommended that coconuts be used as a shade for Pantorhytes are believed killed by natural enemies before they enter the wood. The larva constructs a silk web mixed with brown droppings or frass over the feeding area for protection. Larvae feed on wood and bark for 8 to 12 weeks. Pupation takes 3 to 4 weeks and adults live for only a few days.
23.2.1 Black pod disease (Fungi: Phytophthora palmivora, Phytophthora megakarya)
See diagram 55.23.2.1: Black pod disease
1. This is a common disease of cocoa. The signs of the disease are that black patches appear on the pod, usually down near the tip first. The black patches gradually spread upwards and soon the whole pod and the beans inside it are rotten. This disease is caused by a fungus that grows very fast in cool wet weather. The body of the fungus is like fine white threads of cotton. It makes spores that get into drops of rainwater on the outside of the pod. Then they can be splashed onto healthy pods of trees nearby. These are the things that can be done to stop this disease: 1. Pick the ripe pods regularly every one or two weeks.
2. Take all diseased pods off the tree and carry them away from the cocoa trees and burn them. Do not touch healthy pods after touching diseased pods or you may spread the spores that cause the disease.
3. Do not open ripe pods near the cocoa trees. The disease may grow on the old pods left lying nearby.
4. Cutting down some trees around the cocoa trees and so increase the flow of air through the trees may be possible. This may make the air drier and not such a good place for the fungus spores to grow.
5. Protect apparently healthy pods with copper based fungicides, with or without metalaxyl. If more than one third of the pods get black pod disease, then a spray must be used or the disease will spread to all the pods. To make the spray mixture put half a kilo of bluestone (copper sulfate) into 4 litres of water and stir until it is dissolved. In a separate bucket put half a kilo of slaked lime (hydrated lime) into 4 litres of water and stir until it is dissolved. Pour the bluestone solution and the lime solution into a 20 litre container. Stir this mixture well. Spray this mixture until the spray is dripping off the pods. Also, spray the leaves above the pods and on the trunk. This spray must be used the same day as it is mixed, not later.
6. In Papua New Guinea trunk injection with potassium phosphonate significantly reduced Phytophthora pod rot and increased pod yield. Use of potassium phosphonate or phosphorous acid does not contaminate the environment.
7. The disease may be spread by ants, beetles, the pod borer Characoma, and infected pods and pod husks. Some pest control results from frequent harvesting, immediate removal of infected pods and establishment of ground cover. Selection and breeding of cocoa varieties for resistance to black pod may be possible.
23.2.2 Bark Canker (Ceratocystis fimbriata)
See diagram 55.23.2.1: Bark canker
The bark has been peeled off the trunk to show the canker spreading around the trunk. This disease attacks the trunk and branches of the cocoa tree. If a tree has the canker, the bark may have patches of darker colour. Also, a reddish brown liquid may come out of the bark and turn a rusty brown colour when dry. Insects live in the dying bark and may make any holes in it. When the bark is cut away, you can see the canker. This disease is caused by the same fungus that causes black pod. Always put tar over a cut made when pruning a tree. Pruning tools must be sterilized by dipping them in a 1% sodium hypochlorite solution. Take all black pods away because they carry the canker spores. In small cankers, cut away the bad bark, making a clean cut just outside the canker.
23.2.3 Dieback (Vascular streak dieback virus, VSD)
See diagram 55.23.2.3: Dieback disease
In this disease the top branches of a tree die. The disease starts when leaves turn yellow and drop off. What causes this disease is not known but it may be a virus carried by mealy bugs. Make sure the trees have the right amount of shade. Trees that do not have enough shade may get dieback. Look at the leaves of the trees. Observe whether they have brown leaf edges, or yellow leaves or leaves with light green patches between leaf veins. These things may mean that the trees are not getting enough minerals, and they may need some fertilizers. Kill insects on the trees. If many leaves are killed the tree may get dieback. Prune off the dead branches, and cover the cut ends of branches with tar.
23.2.4 Pink Disease (Botryobasidium salmonicolor)
See diagram 55.23.2.3: Pink disease
In this disease a fungus attacks the branches of cocoa trees. It also attacks branches of other trees like coffee, citrus or rubber trees. The first sign is when fine white threads of fungus are seen on a branch. Later the fungus forms a pink crust over the branch. By the time the leaves drop off the tree and the branch will soon die. To stop this disease: 1. Cut off the diseased branches making the cuts 45 cm below the bad part. Take the bad branches away and burn them. Put some tar or other chemical fungicide over the cut you have made on the tree.
23.2.5 Thread Blight (Corticium incisum, Marasmius species, and other species)
See diagram 55.23.1.1: Thread blight
Seeing this disease is easy if it comes to your tree, because the leaves have fungus threads growing thickly over them. Sometimes the threads are white and sometimes they are a dark colour. The threads are quite thick. This disease makes the leaves die and grow brown. Cut out the diseased branches and burn them.
25. Returns, costs and profits
See 6.9.20.0: Understanding the records
You grow cocoa so that the beans can be fermented and dried properly and then sold for money, so you should calculate the annual profit of the cocoa project.
Returns means all the moneys they have received from selling the cocoa. Cocoa pods ripen at different times, so the beans must be fermented and dried at different times and the money received for the beans will come in at different times.
Record the returns under the 3 headings: Date Amount Sold
(Profits = Returns - Costs). However, costs are divided into two groups. Establishment costs are moneys paid for things that will last more than a year, e.g. a spade and secateurs. So you add these costs and divide them by the number of years that you think these things will last, e.g. Divide by 3 if you think the items can be used for 3 years. This calculation gives us a figure for establishment costs for each year. Production Costs are costs for things that you must buy every year, e.g. fertilizers, fungicides and insecticides.
So (profits = returns - (establishment costs / 3) - production costs)
Net profit for the year = total profit of the 40 cocoa trees / 40, i.e. profit per tree. you can also calculate profit / hectare (ha).
Cultivation of recommended new hybrid cocoa cultivars should bring higher yields and profits.
26. Commercial chocolate
At the chocolate factory the beans are sorted and cleaned, then roasted and winnowed to remove the outer shells to be sold for animal feed. The remaining "inner nib" is crushed then heated to melt the cocoa butter and ground to a thick paste. This paste is called "chocolate liquor" which is then pressed to extract most of the cocoa butter leaving a cake that is ground into cocoa powder. Cooking chocolate is made from moulded chocolate liquor. Dark chocolate is made with chocolate liquor, sugar, cocoa butter, and vanilla. Milk chocolate is made with chocolate liquor, cocoa butter, sugar and milk powder. White chocolate is made with cocoa butter but no chocolate liquor.
The beans are roasted and passed through a complex set of milling processes. The heat of grinding melts the fat and produces chocolate liquor, which is composed of about 55% fat, 17% carbohydrate, 11% protein, tannins, ash. Theobromine, the stimulant alkaloid related to caffeine, is found in amounts ranging from 0.8% to 1.7%. Theobromine may be poisonous to dogs, so do not give your dog chocolate. Less caffeine is also found. The solidified liquor forms the bitter cooking or baking chocolate. The fat removed from the chocolate liquor is cocoa butter that consists mainly of triglycerides in which the middle fatty acid is oleic acid and the two outside fatty acids are saturated, generally stearic acid or palmitic acid. The simple composition of cocoa butter causes a relatively sharp melting point, 30oC to 35oC. However the solid is polymorphic, i.e. it can crystallize in at least three different crystal forms, with melting points varying from 17.3oC to 35oC. Only the fifth of these forms, a so-called beta-3 type, with a melting point of 33.8oC is suitable because if the fat crystallizes in an unstable form it will cause problems. For milk chocolate, the need may be a minimum of 45 g / kg milk fat, 105 g / kg non-fat milk solids, milk sugars mainly, and 30 g / kg water free, fat-free cocoa paste. Cocoa paste is defined as the product prepared by grinding solidified chocolate liquor containing not less than 480 g / kg of cocoa butter but the fat-free specification means there is no minimum need for chocolate to contain cocoa butter. So there is an incentive to replace the expensive and often variable in quality cocoa butter with a cheaper fat. White chocolate does have a minimum content of 200 g / kg of cocoa butter specified and also must contain not more than 550 g / kg of sugar, i.e. it can be over half sugar. Fat bloom is the development of a new phase in a chocolate fat, causing surface disruption with large clusters to give the grey mould-like coating usually due to poor consumer storage. Fat bloom in chocolate is distinguished from loss of gloss which occurs when small crystals on the surface grow into large crystals and scatter light. The use of emulsifiers and stabilizers can greatly affect the rate at which crystal changes occur in the solid state. Various additives, e.g. sorbitan fatty acid esters, are used to control crystallization and phase change in substitute chocolate.
Nutritional information on cocoa powder, per 100g ("Cacao Powder" Van Houten brand)
Energy 1390 kJ
Protein 23.5%
Carbohydrates 45 g (sugars 0.5 g)
Fat total 21% (saturated fats 13.7%)
Fibres 34 g
Sodium 27 mg
Cholesterol 6.3 g
Calcium 130 mg
Iron 22 mg
27. Chocolate recipes
1. Home-made chocolate
Grind 1 to 2 kg of cocoa beans in a manually-operated grinder . Roast the green cocao beans over an open fire, while stirring, until they "pop". However only 75% should be popped or the beans will burn. Peel the popped beans as quickly as possible while they are still hot. Grind the beans with a pestle and mortar and note the bitter taste of the oil produced by grinding. Chocolate made with the oil gives a richer, yet bitter flavour. If you want to use the oil, put small piles of the ground paste on aluminium foil or greaseproof paper on a tray. Leave overnight until the piles harden to form crude chocolate tablets. If you do not want to use the oil, squeeze the paste in cheesecloth until most of the oil is squeezed out to form crude cocoa powder.
2. Aztec "Cacahuatl"
Add the crude powder or the chocolate tablets broken down to a fine powder with a pestle and mortar to cold water in a pan. Add some chilli water, i.e. chopped chillies soaked in boiling water to make a chilli "tea". Add vanilla bean pods and honey. Heat the pan while stirring constantly. When the mixture starts to bubble, quickly remove the pan from the stove and allow it to cool slightly. Put the pan back on the stove and continue to stir until boiling. Repeat the cooling and re-boiling to aerate the chocolate and improve it flavour. The finished Aztec drink should be soft, foamy, reddish, bitter and spicy.
History
These teaching materials were originally written and illustrated by Mr J. A. Sutherland, Faculty of Education, University of New England, Armidale, Australia and later edited by Dr J. Elfick, School of Education, University of Queensland, Brisbane, Australia.