Biological Capital, User Costs and the Productivity of Insecticides in Cotton Farming Systems in Sub-Saharan Africa

This study presents a conceptual framework and then uses field data collected in cotton fields of Côte d’Ivoire to illustrate the dynamics of the interaction between insecticides use, natural biological capital and the productivity of insecticides over time. Results show that the divergence between insecticide pro-ductivity estimates on one hand and, public concern that insecticides are overused on the other hand may not be attributed exclusively to functional specification of estimationmodels. However, some insights into resol-ving the paradox can be gained through disaggregation of the estimates (e.g. by chemical use history) and inter-preting them in the context of the inter-temporal changes that have occurred in the biological capital of production systems over time. A disaggregation of the marginal value products of insecticide by chemical use history shows that in the zones where insecticides have been used for a longer period and crop diversity is narrower, the marginal value products of insecticides are consist-ently higher due to lower biodiversity which raises the economic importance of the chemical in such zones. To ensure long term sustainability of cotton in the region, the study recommends the promotion of targeted insecti-cide management practices that takes cognisance of the differences in the amount of biological capital and the economic value of the potential crop yield that would be saved by the chemical application in the different production systems. It also recommends that panel data consisting of entomological and the state of the agro-ecosystem being studied should be collected concurrently with agro-economic data and integrated into models for estimating insecticides ’ productivity