Insect pests and predators in oilseed rape relative to landscape and site factors

Abstract: In thirty oilseed rape (OSR) fields located in landscapes ranging from structurally poor to complex in an agriculturally dominated region in Eastern Austria, abundance and diversity of OSR pests and arthropod predators were investigated at eight spatial scales. Abundance of pollen beetles was significantly negatively correlated with OSR area. Agrobiont spider species richness revealed the strongest positive response to amount of fallows at intermediate scales. Spider density was positively related to length of road-side strips with maximum effects at large scales. Nutritional condition of both sexes of the common carabids Amara similata and Poecilus cupreus increased significantly with OSR pest abundance. Number and biomass of spiders and carabids were significantly negatively correlated with the density of pollen beetles and stem weevils, indicating that these arthropod predators may prey upon these particularly severe pests of OSR.