SPATIAL SCALES IN ECOLOGICAL PEST-MANAGEMENT (EPM) - IMPORTANCE OF REGIONAL CROP ROTATIONS

The importance of spatial scales and landscape heterogeneity to insect populations is widely accepted in ecology and conservation biology. W hat are the applications to crop protection? Theoretically, insect pes t species with certain characteristic metapopulation dynamics may effe ctively be managed by crop rotation, by applying the same tools as use d in conservation. This strategy may in many cases necessitate regiona lly planned rotations that exceed single farm boundaries. The basic id ea of pest management by regional crop rotation is presented, the theo retical background outlined and agroecological prerequisites discussed . Spatiotemporal patterns of both pest occurrence and the host crop fi eld allocation in the landscape are important. For example, the requir ed degree of isolation between host crop patches cannot be achieved wi th regionally covering major crops, e.g. cereals. The dispersal abilit y of the pest determines the overall spatial scale at which the rotati on is practised. Recruitment from wild hosts must not be excessive. Th ese aspects .re illustrated with example species, the cabbage root fly , Delia radicum a possible target for regional management, and the rap e pollen beetle, Meligerhes aeneus, an unlikely target. Regional rotat ion and biological control are not conflicting strategies, as the crop -pest systems most promising for regional management are the least pro mising for biological control.