The hazard of postharvest pest losses is ubiquitous in peasant farming systems; as a result, farmers invariably have some response to the threat of these losses. Responses to postharvest pests may be more extensive than to field pests, even when, by statistical measures, the usual levels of losses are comparable. In studies of pest management practices in three contrasting areas in Kenya, it was found that farmers virtually always rely on an array of techniques and strategies, usually including both older and more modern practices. There is considerable variation among regions in the techniques used, due not only to climatic and socioeconomic factors, but also to variations in cultural history and preferences. The ways in which management practices have changed over time also vary by region. The major changes have been related to overall system change. Four main sources of change have been paramount: (1) population growth and the intensification of land use; (2) the introduction of new cash crops; (3) the introduction of new marketing infrastructure; and (4) the perception of increased environmental risk. Their effect on the replacement of older practices by newer ones is often interrelated. Traditional techniques are often based on materials derived from bushland, but increasing population density makes these difficult to continue as bushland and its common property resources disappear. Simultaneously, tolerance for losses is reduced as land availability is constrained. With the introduction of a cash crop infrastructure, new methods of pest management, especially pesticide use, become more readily available and may spread rapidly. Areas with good market infrastructure but varying population density may still differ considerably because with abundant land it is possible to compensate for expected losses by additional planting.
A study of an FAO project to improve postharvest management through earlier harvesting and a redesigned storage crib indicate some reasons for its lack of widespread acceptance. Little or no attempt was made to adapt techniques to varying circumstances; instead, a single “solution” was meant to be applied across areas of vastly different conditions. In many cases, this project represented a radical response to a problem farmers considered they were coping with acceptably using existing methods. Although it probably represents an improvement over traditional storage methods in purely technical terms, the new technique also often involved major costs, readjustments, and cultural disruptions that may not have been anticipated by its designers. More likely to succeed would be a strategy that begins with some of farmers' existing practices and whose objective is to develop and offer a range of possible improvements from which farmers could select individual components appropriate to their conditions and needs.