Ornamental horticulture has experienced a marked growth in the past 40 years and has developed into one of the major economic branches of modern agriculture. Development of this industry is based on the supply of high quality flowers and plants, thus making the control of viral and other diseases a prerequisite. This manual explores the topics of virus classification, transmission, purification, detection, diagnosis and control. It also describes the viral diseases found in major flower bulbs, cut flowers, flowering potted plants, and some of the most important bedding plants.