ABSTRACT
Most biological control programs have been conducted in orchards and in protected environments because these are considered to be more stable and permanent ecosystems than annual-crop agroecosystems (Huffaker and Messenger, 1976). Several authors have claimed that insect populations are more stable in complex orchard communities because a diverse and more permanent habitat can maintain an adequate population of the pest and its enemies at critical times (van' den Bosch and Telford, 1964). Orchards are semipermanent, relatively undisturbed systems, with no fallow; and crop rotation does not apply in the short term, so particular biological situations affecting insects occur in these systems.
