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Development of mycoinsecticides for cocoa mirids

Funders

Department For International Development (DFID, UK)

Partners

Cocoa Research Institute of Ghana (CRIG), Natural Resources Institute (NRI)

Project Description


Mirid damage on cocoa pod in West Africa

Problem/Issue. Cocoa is the main export crop of Ghana, maintaining directly or indirectly the livelihoods of over 6 million people. Cocoa mirids (Heteroptera: Miridae) are the most important insect pests, causing losses estimated at 100,000 tonnes or 25% of the crop. The nymphs and adult mirids feed on the stems, branches and pods causing them to wilt above the point of attack. The feeding punctures also serve as points of entry for plant pathogens. They often aggregate in pockets where conditions are particularly favourable e.g. where there is a break in the shade canopy.

Measures to Date. Current recommended control methods involve four sprays of inorganic pesticides like Lindane or Propoxur during the main mirid season (August-December), a programme that is rarely followed by farmers due to high cost of insecticide and environmental concerns. The cost of chemical control is estimated to be between 25 and 35 sterling pounds per hectare, but surveys conducted by CRIG Farming Systems Unit showed that only 0.7% of the cocoa farmers had sprayed their crop and only 0.4% had applied the recommended number of sprays, often not at the appropriate time. Chemical control methods have therefore not led to acceptable control of the mirids.

Project Activities. CABI Bioscience has a wealth of experience in the use of entomopathogens as biocontrol agents for the management of pests. In collaboration with CRIG, CABI staff conducted field surveys for pathogens in all the cocoa growing regions of Ghana. CRIG staff were trained in practical survey methods including insect collection and maintenance as well as pathogen isolation and culturing. Further training in advanced insect pathology techniques was provided at CABI Bioscience African Regional Centre. CABI mass-produced entomopathogenic fungi isolated from mirids collected from both within and outside Ghana, and sent them to CRIG. These pathogens are now being evaluated for the potential as biological control agents for the cocoa mirids.

Achievements So Far

The entomopathogenic fungus Beauveria bassiana was successfully isolated from a mirid collected from Ghana and isolates from mirids collected in Papua New Guinea have also been supplied to CRIG. Tests on the pathogenicity and specificity of these pathogens together with their responses to different environmental conditions are underway.

What Next

Once the most promising fungal isolate has been identified, studies should be done on the most appropriate formulation for maximum impact on the mirid population. The application methods most appropriate to this system will also have to be developed.

Dr. Roy Bateman (Co-ordinator) r.bateman@cabi.org

Start date: 1998

End date: 2001

 

 
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Contact CABI Commodities:
CABI Commodities Coffee Co-ordinator - Dr. Peter Baker - p.baker@cabi.org
CABI Commodities Cocoa Co-ordinator - Dr. Keith Holmes - k.holmes@cabi.org
CABI Commodities Project Administrator - cabi-commodities@cabi.org