1. BY
Ralph Kwadwo Osei
The effects of cocaoa mirid Distantiella theobromain cocoa
plantations”
Ghanaian experience
2. • CLASS: Insecta
• ORDER: Hemiptera
• FAMILY: Miridae
• GENUS: Distantiella
• SPECIES: Distantiella Theobroma (Dist)
Sap suckers
Toxic saliva causes Pod Spotting
Cocoa is an economically important crop in many parts of the humid tropics.
West Africa produces 70% of the global market (ICCO 2010/11)
The mirid was first detected in 1908 after few years of introduction of the
Cacao crop in Gold Coast (Ghana) in 1876 from Fernando Po (now Bioko in
Equatorial Guinea). But the Mirids originally can be traced back to the
Amazon region of Brazil where the crop also originates.
3. Crop damages by mirids (mainly S. singularis and Distantiella Theobroma) represent one of the major
constrains to production.
Losses to mirids can be estimated around 30-40% (Awudzi et at 2016)
Life Cycle
1. Egg
The Adult female oviposit an average of 73 eggs on the developing fruit or on the tree backs. And the
incubation period is 14 days.
2. Nymph
There are five(5) nymphal instar development stages from egg to adult, and last a total of 41 days.
3. Adult.
A fully grown adult starts the reproduction cycle again and can live a minimum of two (2) generations
or more.
Population Dynamics.
1. Increasing population phase = June
2. Population at peak = September
3. Population decline = October
Mirids are present in cocoa farms all year round but with different peak periods, (Awudzi et at 2016).
4. Damages
• D. Theobromae (Dist) feeds on the green twigs and young pods of
Cacao causing lysis of sub-epidermal cells and tissue necrosis.
fruit Stem Leaves Whole Plant
1. Abnormal Shape 1. Canker on woody stem 1. Abnormal leaf fall 1. Seedling Blight
2. Discoloration 2. Dieback 2. Yellowing of dead 2. Plant dead: Dieback
3. Extensive mould 3. Discoloration of Back
4. lesions: Black or brown
depending on species
4. Internal red necrosis
5. Malformed Skin
6. Fruit/seed Rot
5. Mould growth on lesion
6. Galls
6. Control
1. Chemical Application:
Two(2) times chemical application from July-August at the beginning of mirids population
increases in the ecosystem. One month interval has been effective, the CODAPEC program by the
government of Ghana, (Asnate et al. 2002)
Benefits
Increase yield
Hindrance
Pesticide application on routine rather than a need can cause excessive pesticide use with
negative environmental consequences including loss of beneficial insects.
2. Integrated Pest Management (IPM):
By assessing pest population with
a, By Visual hand height method (For nymph) or
b, By Mirid pheromone trapping (winged adult males)
c, Use of climatic data like rainfall amount, temperature and relative humidity
Understanding the population dynamics of insect pests is crucial for monitoring, forecasting and
designing IPM programs (Dormon et al 2007)
7. Control
3. Biological Control:
1. The black ant (Dolichoderus thoracicus) has been used in some
farms as a control measure.
2. Another ant (Oecophylla smaragdina) has also been used although
this one can be aggressive.
4. Genetic Control:
Hybrid cocoa varieties are more resistant to mirid attack than the
Amelonado varieties, (Anikwa et al, 2010)
9. Conclusion
Cocoa is the main agricultural economic crop of Ghana and it contributes
immensely to the GDP of the nation. The golden pod’s (Cocoa) major
enemy are the mirids and therefore requires appropriate methods to
control their population below the economic thresh hold.
• Recommendation
In Ghana and most West African countries, mirid control is carried out
using a calendar-date system (August to December but omitting
November).
This is based on work performed on mirids population dynamics decades
ago (example Raw 1959, Owusu-Manu 1974) and not on current or
expected population trends.
A change, targeting the wingless nymph with less mobility in May will
reduce the population of the adults by June where their population starts
to build up and difficult to control because of high mobility in flight.
10. References
• G. K. Awudzi, A. R. Cudjoe, P. Hadley, P. E. Hatcher, A. J. Daymond,
Optimizing mirid control on cocoa farms through complementary
monitoring systems, 20 May 2016.
• Akua Konadu Antwi-Agyakwa, Susceptibility of field population of
Cocoa Mirids, Shlbergella singularis Haglund And Distantiella
Theobroma (Distanat) to bifenthrin, August 2013.
• https://www.icco.org/about-cocoa/pest-a-diseases.html .
(International Cocoa Organization)
• http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=1
9274. (By, Sarfo, J. E.; Adu-Acheampong, R.; CABI, 2015)
