Natural community beneficials in cropping systems are interlinked with surrounding vegetation matrices. Their biodiversity is affected by numerous farmland approaches and activities. But much of the biological aspects of the beneficials, their specific interrelationships, differences in relative abundance, performance, and management in and between agroecosystems, geographical areas, climatic zones, etc. are yet to be determined or determined in detail. The ecological planning, selection, adaptation, and management of beneficials in a given crop may initially appear costly if just the direct immediate system inputs and profits are considered (Dahlberg, 1992). The measures to enhance diversity and efficiency of beneficials can be difficult, and may not always be feasible. For this reason, each agricultural situation must be assessed separately (Altieri et al., 1993).
Management of beneficials based on current knowledge must be considered as developmental for now. Changes in ecological optimization and stability concepts and implementation will follow further crop structure analysis and landscape diversification research, on-farm trials, and successful IPM examples under variable environments. Legume-based crop rotations, recognized as stabilizing crops, used to improve soils and crop yields, may serve to increase the diversity of beneficials, and may play a significant role in the bilateral drift of beneficials to annuals.
The effects of natural enemies on target pests have economic implications. It is possible to evaluate numerically the ecological value of certain species within a complex net of relationships and connections. We may not appreciate or understand the role or the importance of a given species until after its disappearance, and there may be some insects or insect groups not directly determined to be beneficials in an economic sense, but that may contribute in other ways, such as to the beauty of the environment (Martis, 1988). This could occur in natural systems and in agroecosystems via landscape diversification. Butterflies flying over flowering meadows, hedgerows, weedy ecotones, roadsides, or similar biocorridors improve the often tiring effect of visually plain, monotonous monocultures. Simply stated, biodiversification can be used to improve the aesthetics of the farmland.
This chapter is not an exhaustive review. We have highlighted some key factors, outlined some of the complexities involved in the biology, pathways, and population dynamics of insect natural enemies and their management, cited references for more detail, and mentioned in brief the need for further research.
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