DISEASES,PESTS AND PARASITES OF

PRE-HARVEST COCOA

BYDENNIS OWUSU BOATENG (TECHNICAL OFFICER)

BUNSO COCOA COLLEGECSSVD CONTROL UNIT (COCOBOD)

DISEASES

• A disease a disorder that generally affect normal activities and functions of living things (animals and plants).

• Some of these functions are reproduction, sensitivity, translocation, flowering and excretion etc.

• It is often caused by an infection.

Swollen Shoot Disease• History– In 1937 a farmer, Yaw Sarbeng brought to the notice of

the Agric Department some swellings on cocoa chupons which were killing the trees. Later on, one Dr. Posnette in 1938 – 1939 proved that the disease was caused by a virus

• Importance– Affects cocoa trees causing defoliation, yield reduction

and death of the tree. Cocoa Swollen Shoot Virus Disease is an infectious disease which spreads to other cocoa farms if not controlled early. May destroy young cocoa farm within 18 to 24 months.

• Causal Agent: – The disease is caused by a virus.

• Vector: – The disease is spread by female mealy bug.

• Symptoms– Mosaic in the leaf.– Swellings on chupons and fan branches.– Mosaic on pods – Round pods.

• Alternate Host:– Some identified forest trees have the virus and can

infect cocoa in the field.

– These include:

• Cola chlamydantha -Kra-bise, Asenkrobia• Sterculia trangacatha -Foto• Adansonia digitata -Odadee• Ceiba pentandra -Onyina• Combretodendron -Esa macroparpum

• Control– Infected trees and contact trees are destroyed by

cutting out below ground level.– Trees cut are packed away from the farm.– Re-inspection of outbreak farms is done monthly

to further destroy trees showing symptoms.– Outbreak is considered controlled if no symptoms

are found after several inspections.

Black pod disease

• Importance– Black Pod is the most important fungal disease of

cocoa worldwide and results in the browning, blackening and rotting of cocoa pods and beans. Black Pod is caused by a fungus known as Phytophthora sp.

– The fungus may also grow into the cushion through the pod stalk and enter the trunk to cause Canker.

• There are two types found in Ghana and these are:– P. palmivora – less destructive– P. megakarya – very destructive

• Symptoms – Small brown spot on pod which grows darker and

expands rapidly.– Whitish spores (seeds) are produced on the brown

surface.– The whole surface of the pod may become black

within 14 days.

Mode of transmission

• Healthy pods in contact with infected pods.• Rain drops hitting infected pods splash spores onto

healthy pods.• Drips of water from infected pods falling on healthy pods.• Pods in direct contact with infected soil.• Through the activities of pests and rodents.• Through harvesting implements and contaminated

hands.• Through carrying of infected pods from one farm to

another farm.

Control

• Cultural Control– Reduction of shade trees.– Regular weeding.– Draining standing waters.– Regular harvesting.– Remove chupons and reduce heavy canopy to

admit light.– Remove diseased pods from the farm to an open

space and either burn or bury them.

• Chemical Control.– This involves spraying of recommended fungicides

to coat the pods against the fungus (Phytophthora sp). It should be noted that spraying must start as early as cherelles appear. Spraying must be done every 3 weeks intervals. About 6 – 9 sprays per year are required depending on the length of the rainy season.

– Spray early on a day when the weather is clear, for the chemical to get the chance to dry on the pods. If it rains within 3 hours of spraying then spray again.

– Note: For effective control of black pod, the two methods should be combined.

PESTS

• A pest is any unwanted organism that causes a problem to agriculture.

• A pest can idea be a plant or animal.• A insect become a pest when it competes with

other living things for other resources.

INSECT PESTS

• There are two major insect pests of pre-harvest cocoa, these are:1. Capsid (Akate)2. Bathycoelia thalassina (Atee)

• Minor pest are stem borers and termites

Capsid / Mirids• Capsids are the number one insect pest on cocoa in Ghana.

These insects use their needle-like mouthpart to pierce the surface of cocoa stems, branches and pods; and suck the sap of the cocoa tree. While sucking, they inject toxic spit into the plant. This causes the dying of internal cocoa tissues.

• Infestation on cocoa pods results in minor direct losses, if any. Beans from these pods are generally not affected but may be a little smaller than without infestation.

• The many little scars on the pods are an easy target for black pod, which often causes more losses than the mirids itself.

• Attack on shoots and young branches reduces the canopy of a tree, there by making it vulnerable to other pests and diseases.

• Young cherelles may also be destroyed.

Types

• There are two types found in Ghana and these are:– Distantiella theobroma – black capsid– Sahlbergella singularis – brown capsid.

• Minimum occurrence – February – July • Maximum occurrence – August – January• Six (6) capsids per 10 trees indicate high and

damaging population level.

Alternate Host Plants

1. Kola tree species2. citrus 3. silk 4. cotton tree.

Control

• Cultural control– Mirids are a problem in farms where shade is thin or

non- existent. – This happens when shade or neighbor trees are felled,

when cocoa trees die due to other reasons or when cocoa farms are rejuvenated.

– The following options are suggested to avoid gaps in the canopy and manage mirids.

– Maintain a complete canopy– Remove chupons regularly– Maintain a healthy and balanced ecosystem.– Rational pesticide use

• Chemical Method– Spray with recommended insecticides such as

Confidor, Atrazin, Actara.– Recommended spraying equipments:– Motorized Knapsack machine – for mature cocoa

of over 2 years.– Hand – operated sprayer (MATABI) – for young

cocoa under 2 years.

Bathycoelia thalassina (Atee)

• These are large green insects which feed on cocoa pods.

• They lay their eggs on leaves, trunks and branches. They pierce the pod husk with their mouth parts and suck out the content of the beans.

• As a result young pods turn yellow and then black, large pods stop growing and becomes yellow

Control

• Spray with recommended insecticides. Also hand pick any visible bugs.

• Good farm sanitation and management practice may help to reduce their occurrence.

Stem Borer

• This is a moth. Losses from this insect are usually low but a high number can seriously affect yield and tree health.

• Stem borer has been said to spread as a pest in cases of heavy pesticide abuse on trees, which kills off the natural predators of this pests.

• However from the late 1990s onwards, stem borers have become more noticeable, even on farms where no pesticides are used.

• A further problem is that stem borer entrance holes also serve as entry points for diseases such as Canker.

Symptoms

• Presence of sticky sap on cocoa tree bark.• Attacked branches loose their leaves, dry out

and die off.• Presence of silk threads on branches.

Control

• Use pesticides rationally to keep insect pests in check and to preserve natural enemies of stem borer.

• Plant a barrier crop that is not attractive to stem borers such as sweet potato, cocoyam, leucaena sp.

• Practice spot application of pesticides.

Termite

• Termites may live either in the canopy or in the underground.

• They attack seedlings or young trees at the base and without control, trees may wilt and die.

• This type of damage can also happen to suckers of full-grown trees. In full-grown trees, some types of termites attack injured and dead wood. Other types chew into the roots and tunnel up into the branch.

• Termites can attack living cocoa wood. They chew the wood, which causes openings for diseases such as Canker.

Symptoms

• Presence of mud tents on the trunk.• Attack results in severe and sudden wilt of

branches.

Control

• Keep trees undamaged to make them less attractive to termite attack.

• Try spot application of botanical such as neem rather than chemical pesticides (as chemical pesticide may kill the natural enemies of termites).

Plant Pest or Parasite

• Parasite, organism that lives in or on a second organism, called a host, usually causing it some harm.

• A parasite is generally smaller than the host and of a different species.

• Parasites are dependent on the host for some or all of their nourishment.

• Plant parasites which affect cocoa that can be found in Ghana is called mistletoes.

• Another plant pest or parasite is called witches broom which is not found in Ghana.

Mistletoes

• Mistletoe belongs to the family Loranthaceae.• Mistletoes are plant parasites that live on

other plants to obtain food and water. • Mistletoes can infest many plants including

cocoa, and if unchecked can cause serious problems in cocoa farms.

• Infestation by Mistletoe results in death of a branch from the point of attack, with heavy infestations leading to the death of many branches.

Types

• There are species of mistletoes in Ghana.• One species (Tapinanthus bangwensis) is

recognised by its red flowers and berries, it flowers twice a year in Ghana and can live for up to 18 years.

• Another, is also caused by Phragmanthera incana causes about 20% infestation and has yellow flowers and blue fruit.

Alternative host

• Citrus tree• Cola tree• Pear tree

Control • Cultural control is so far the only method that is

effective; chemicals are not effective, as it is impossible to apply them safely and efficiently.

• Good maintenance of top shade to prevent germination of Mistletoe seeds is a useful long-term measure, but manual pruning is still the best method for immediate results.

• Cutting-out/removal of Mistletoes is recommended every other year.

• The recommended time is when the Mistletoe is in flower as this makes it easier to spot them in the cocoa canopy.

THANK U