Landscape Structure and Extra-Field Processes: Impact on Management of Pests and Beneficiais
Although individual crops or fields can be viewed as fully functional ecosystems in themselves (see Chap. 1), it is clear that crop fields are also influenced by adjacent crop and noncrop habitats. These influences involve the exchange of species (pests and beneficiais) and materials (e.g., soil, water, nutrients) and may occur at local or regional spatial scales. From the perspective of pest management, it is important to know how adjacent crop and noncrop habitats influence the population and community dynamics of the pests and beneficiais within particular cropping systems. Although integrated pest management (IPM) programs have generally focused on the crop or individual fields as the unit of management , and thus tended to ignore the role of extra-field processes, renewed interest in "area-wide" and "preventative pest management" systems necessitates a different approach. Because of the tight coupling of ecological processes occurring within fields and those occurring external to crop fields, it is imperative that pest managers begin to understand this linkage and how to manipulate extra-field habitats to facilitate effective pest management .