Introduction

Weed scientists usually cite pervasive crop yield losses due to weeds and substantial direct and indirect costs of weed control to justify research and extension budgets (see Chapter 1). Reductions in costs and yield losses should also be used to evaluate the progress of scientists in solving weed problems. Ultimately weed costs to agriculture are determined by how farmers and ranchers manage weeds, not by papers published or field days organized. In temperate and tropical regions, field crop farmers who use mechanization, cattle ranchers, dairy farmers, vegetable and fruit growers, and smallholders on hillsides all devote time and resources to weed management. What is the role of research and extension in enabling this wide diversity of farmers to manage their weeds better?

This chapter examines the implications of farmer–extensionist–scientist interactions for the development of improved weed management. The first sections review historically how humans have learned to manage weeds. The chapter then analyzes scientist, extensionist, and farmer perspectives on weeds. The final sections describe how farmers, extensionists, and scientists can collaborate to develop field- and farm-level weed management strategies better adapted to weed patchiness and uncertainty. Case studies from the USA and Central America illustrate possible working relations among scientists, extensionists, and farmers.