From pattern to process: Towards mechanistic design principles for pest suppressive landscapes

The challenge to reconcile agricultural production with the conservation of biodiversity and associated ecosystems services has triggered interest in the design of pest suppressive landscapes. However, the uniqueness of species-specific responses to management and landscape context hamper our ability to make generalizations for landscape design, and we often lack quantitative indicators to make inferences about the pest suppressive potential of landscape designs. Here I examine the literature to underpin design principles based on source-sink theory. The potential of landscapes to support herbivore populations is associated with the area of source habitat, source strength, and the ability of herbivores to detect host plants. The potential of natural enemies to suppress herbivore populations is associated with their potential for numerical response, time to colonization and natural enemy diversity. Insecticide applications and other intensive management practices can turn treated fields into sinks. The analysis reveals that landscape features or management practices influence multiple processes at the same time, and that well-documented landscape features associated with high pest suppression potential generally discourage herbivores and/or favour natural enemies. The evaluation of landscapes in terms of source habitats for specific herbivores and their natural enemies may reveal context-specific information that allow a better quantitative understanding of pest suppression potential of landscapes.