Economic benefits of biological control of cassava green mite (CGM) in Ghana
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Date
2016-07-18
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Development and Agricultural Economics
Abstract
The aim of the study was to evaluate the economic impact of biological control of cassava green mite
(CGM) in Ghana by using the natural enemy Typhlodromalus manihoti. Both primary and secondary
data were used for analysis. In total, 714 cassava producing households were drawn from 17 districts in
seven regions of Ghana by employing a combination of proportional, purposive, simple random, and
systematic random sampling techniques. Formal interviews with the use of standardized structured
questionnaire were combined with field/farm visits to elicit information for the study. The ‘with and
without’ comparison and trend analysis of secondary data were performed to evaluate project impact.
The economic surplus model was used to estimate net benefits of biological control of CGM in Ghana in
terms of Benefit-Cost Ratio (BCR), Net Present Value (NPV) and Internal Rate of Return (IRR). Following
the release of about 2,344,817 CGM predators (T. manihoti) in seven regions of Ghana between the year
2007 and 2012, the study found evidence of T. manihoti presence in beneficiary communities. However,
the level of establishment and extent of spread were markedly different across regions and districts in
Ghana. The CGM biological control project in Ghana was found to have been successful in reducing
CGM populations on cassava fields, reducing cassava root losses, improving productivity and
profitability under varying climatic conditions and soil types. Biological control of CGM leads to higher
economic gain to farmers and the country as a whole. Biological control of CGM was found to generate
economic returns (NPV) of US$228.5 million, a BCR of 5,393.74 and an IRR of 3,424% at a discount rate
of 20% for the period 2006 to 2046. Sensitivity analysis showed that the returns are robust even at
higher discount rate (50%) and under pessimistic assumptions about yield gains. The overall project
impact is expected to be higher when benefits to ecological and human health, which are usually
difficult to quantify, are considered. Periodic inoculation in released communities and fresh releases in
new communities are recommended if the country is to realize the full benefits of biological control of
CGM.
Description
An article published by Journal of Development and Agricultural
Economics
Keywords
Biological control, cassava green mite, economic gain, impact, Typhlodromalus manihoti.
Citation
Journal of Development and Agricultural Economics Vol. 8(7), pp. 172-185,