In step with the growing activity in the post-harvest sector, issues gradually arose concerning the social, cultural and economic impacts of this commitment. Faced with the low level of acceptance of certain recommendations given in extension that are purposeful from a technical point of view - such as installing rodent guards on traditional granaries or treating dried beans with neem oil for protection against seed beetles -GTZ was forced to broaden its perspective and give greater consideration to the framework conditions of the overall post-harvest system. Measures that called for fundamental changes in traditional storage systems, such as introducing the "narrow crib" type of dry storage or the "Cacaveli" type of storage house suitable for fumigation, were not adopted by the farmers for a variety of reasons. As, in addition to the resourceinput required, economic competitiveness is also a major aspect in the affected farmers' decision to accept an innovation, the latter dimension increasingly gained attention. Although in principle cost-free for the farmers, the biological control of the LGB must prove itself to be beneficial according to economic criteria.
These experiences triggered a series of socio-cultural and above all socio-economic studies aimed at contributing to an improved understanding of this phenomenon. The socio-cultural aspects cannot be addressed in further detail within the scope of this brochure. We draw attention here to the material contained in the studies by Albert (1992), Henckes (1992) and Mutlu (1998) and in the extensive surveys carried out within the "Post-harvest protection for small farmers" project in several countries of East and West Africa. According to these studies, the issues of workload and of gender-related role distributions in farming households play a crucial role, as do the preconditions and the structure of decision-making processes concerning the use and marketing of stored products.
The economic appraisal of post-harvest protection measures centres on four questions:
1. How high are the real losses suffered in farm-level stores?
2. How competitive in economic terms are innovative post-harvest protection measures compared to the methods already practised by farmers?
3. What are the effects of introducing new post-harvest protection techniques into farming systems upon the standard of living of rural families?
4. What are the macro-economic impacts of different approaches to loss reduction?
The following sections describe the various approaches taken to answer these questions and present the findings for the exemplary case of LGB control.