Pests and pathogens cause enormous damage to crops and natural vegetation but their effects are usually studied separately. This new review volume covers both subjects with the aim of establishing where their effects overlap or where there are essential differences. Plant responses to pests are triggered by injury to photosynthetic tissue. The usual physiological response is a modification of growth to minimize damage. In populations of wild plants, a loss of competitive and reproductive fitness normally occurs, whereas crops suffer from a lower harvestably yield. By reviewing areas of commonality it is intended that crop loss assessment models can be refined and improved, particularly since pests and pathogens often affect crops simultaneously. Recent advances in the understanding of basic wound responses, and both intra- and inter-plant signalling, reveal the extent to which the biochemistry of different defence mechanisms may have diverged from common origins in the course of evolution. Understanding the reasons for this divergence will, in the long term, greatly benefit efforts in plant breeding. It is intended for plant researchers; postgraduates and final year undergraduate students in plant biology (particularly plant pathology), agricultural botany and entomology.