This comprehensive volume presents indispensable and up-to-date information on viroids and viroid diseases. It provides a single source of information on the properties of viroids, the economic impact of viroid diseases, and methods for their detection and control. It examines the diseases associated with different plant species, the geographic distribution and epidemiology of viroids, diseases of possible viroid etlology, and the future applications of viroids. The four eminent editors of this watershed volume have assembled an international group of more than 70 scientists who have substantial experience with viroids and viroid diseases. They have produced a cohesive and comprehensive work that can be used by students, researchers, extension agents and regulators. It may also be of a great value to science managers, policy makers, and industries in formulating policies and products to obtain viroid-free plants and control viroid diseases. The information on plant quarantine and certification programs will help anyone concerned with the safe movement of plant material across international boundaries or within a single country.