Phytoplasmas are a worldwide issue in plant health. A range of serious diseases are caused by these bacteria in major crops around the globe. Knowledge of the importance of phytoplasmas as plant disease agents has advanced rapidly over the last decade with an increased interest in the impact of these pathogens on important field and horticultural crops as well as ornamental plants. This comprehensive volume brings together current research on phytoplasmas, covering their biology, taxonomy and genomics as well as their interactions with plant hosts and transmission by vectors.