Economics of biological control of cereal stemborers in Eastern Africa: a case study of maize and sorghum production in Kenya
Midingoyi, Soul-Kifouly Gnonna
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The International Centre of Insect Physiology and Ecology (icipe), undertook a biological control (BC) programme for control of stemborers from 1993 to 2008, to reduce cereal yield losses due to stemborer attack in East and Southern Africa. The programme released four biological control agents—Cotesia flavipes, Cotesia sesamiae, Telenomus isis and Xanthopimpla stemmator—to control the economically important stemborer pests Busseola fusca, Chilo partellus and Sesamia calamistis. The purpose of this research was to assess the ex-post economic impact of the BC program among smallholder farmers in Kenya. Specifically, the study sought to: i) determine the productivity-effects of BC at farm level, ii) assess the impact of BC on food security and poverty and iii) estimate the global welfare-effect from the BC. Primary data was obtained from biological and household surveys. The household survey was conducted to collect socio-economic data on 600 households randomly sampled across maize agro-ecological zones of Kenya. Secondary data included time-series evolution of maize and sorghum production, yield, cropped area, market prices, price-elasticity of supply and demand and GIS information of the release locations. Methodologically, econometrics-based damage control function framework was adopted to address the first objective, the counterfactual framework using continuous treatment regression analysis for the second objective and economic surplus model analysis to address the third objective. Findings from productivity analysis show a reduction of insecticide use with the BC, thus demonstrating the potential environmental hazard-reducing effect of BC. Additionally, results show that BC has a positive impact on productivity and the derived marginal physical product show that 1% increase in BC level is associated with at least 12 kilograms per hectare increase in yield. The dose response functions (DRF) and the Marginal Treatment Effect (MTE) from the continuous treatment models provide evidence that BC has had a positive and increasing impact on poverty outcomes and food security components exept dietary diversity. For poverty, on average one percent increase in BC intensity is associated with a US$ 1.15 increase of household expenditures and a 0.5% reduction in poor households. With regards to food security, a one percent increase in BC level increased food expenditures by US$ 1.24 and calorie intake by 6.94 Kcal, and reduced the number of food-insecure households by 0.16%. Findings from the global welfare-effect show that BC intervention has contributed to an aggregate monetary surplus of US$ 0.74 billion to the Kenyan economy over 20 years period (1993 to 2013), with 76.71% ($US 568.06 million) from maize and the remaining 23.29% ($US 172.45 million) from sorghum. The net present value was estimated at US$ 142 million for both crops. The attractive internal rate of return (IRR) of 113% as well as the estimated benefit–cost ratio (BCR) of 276:1, illustrate the efficiency of investment in the BC research and intervention. The estimated number of people that could be lifted out of poverty was on average 57,400 persons (consumers and producers) per year, representing an annual average reduction of poor populations of 0.35%. These findings underscore the need for increased investment in BC research to sustain cereal production, and developing BC can be seen as an additional environmentally-friendly tool in the fight against food insecurity and poverty in Kenya. Policy implications are two-folds: boosting the effectiveness of the BC in regions with low level of control through augmentative and conservative BC, and up-scaling the BC strategy to regions with serious stemborers invasion.