Life systems of polyphagous arthropod pests in temporally unstable cropping systems

Annual cropping systems consist of a shifting mosaic of habitats that vary through time in their availability and suitability to insect pests. Agroeco system instability results from changes that occur within a season with cro p planting, development, and harvest. Further instability results from cont inuous alterations in biotic and abiotic insect life system components and from agricultural inputs. Changes to agroecosystems occur across seasons wi th changing agricultural practices, changing cropping patterns, and technol ogical innovations. Much of this instability is a result of events unconnec ted with pest management. The abilities of polyphagous pest species to move among and utilize differe nt habitat patches in response to changes in suitability enable the pests t o exploit unstable cropping systems. These pest characteristics determine t he location and timing of damaging populations. Habitat suitability is infl uenced by plant species and cultivar, crop phenology, and agricultural inpu ts. Pest movement is affected by a suite of intrinsic factors, such as popu lation age structure and mobility, and extrinsic factors, including weather systems and habitat distribution. The life systems of three selected polyphagous pests are presented to demon strate how an understanding of such systems in agricultural ecosystems impr oves our ability to predict and hence manage these populations.