Diseases And Pests Of Pre Harvest Cocoa

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Transcript of Diseases And Pests Of Pre Harvest Cocoa

  • 1. DISEASES,PESTS AND PARASITES OF PRE-HARVEST COCOA
    BY
    DENNIS OWUSU BOATENG (TECHNICAL OFFICER)
    BUNSO COCOA COLLEGE
    CSSVD CONTROL UNIT (COCOBOD)
  • 2. 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.
  • 3. 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.
  • 4. 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.
  • 5. Alternate Host:
    Some identified forest trees have the virus and can infect cocoa in the field.
    These include:
    Colachlamydantha-Kra-bise, Asenkrobia
    Sterculiatrangacatha-Foto
    Adansoniadigitata-Odadee
    Ceibapentandra-Onyina
    Combretodendron-Esamacroparpum
  • 6. 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.
  • 7. 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 asPhytophthora sp.
    The fungus may also grow into the cushion through the pod stalk and enter the trunk to cause Canker.
  • 8. 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.
  • 9. 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.
  • 10. 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.
  • 11. 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.
  • 12. 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.
  • 13. INSECT PESTS
    There are two major insect pests of pre-harvest cocoa, these are:
    Capsid (Akate)
    Bathycoeliathalassina (Atee)
    Minor pest are stem borers and termites
  • 14. 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.
  • 15. Types
    There are two types found in Ghana and these are:
    Distantiellatheobroma black capsid
    Sahlbergellasingularis brown capsid.
    Minimum occurrence February July
    Maximum occurrence August January
    Six (6) capsids per 10 trees indicate high and damaging population level.

  • 16. Alternate Host Plants
    Kola tree species
    citrus
    silk
    cotton tree.
  • 17. Control
    Cultural control
    Miridsare 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
  • 18. 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.
  • 19. Bathycoeliathalassina (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
  • 20. Control
    Spray with recommended insecticides. Also hand pick any visible bugs.
    Good farm sanitation and management practice may help to reduce their occurrence.
  • 21. 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.