The overuse and misuse of insecticides some four decades ago created major environmental problems and was followed by the development of an ‘integrated pest management’ approach to crop pests. This approach utilizes a combination of host plant resistance and cultural, biological and chemical control methods. Crop improvement programs emphasize the breeding of crop varieties with multiple resistance to pests, and resistant varieties developed in recent years represent some of the greatest achievements of modern agriculture. This book presents a broad overview of host plant resistance to insect pests. It shows how plants can defend themselves naturally and how insects have adapted to overcome these mechanisms through coevolution. It also describes screening and breeding for insect resistance.