All aerial plant surfaces, including leaves, stems and flowers are inhabited by diverse assemblages of microorganisms, including filamentous fungi, yeasts, bacteria, and bacteriophages. These organisms have profound effects on plant health and thus impact on ecosystem and agricultural functions. This book is based on proceedings from the 8th International Symposium on the mircobiology of aerial plant surfaces, held in Oxford 2005. This is a five yearly conference which brings together international scientists and provides a unique opportunity to discuss developments in this field.