Crop diseases are typically caused by a variety of abiotic and biotic factors. Among these biotic factors, microbial plant pathogens such as fungi, bacteria, phytoplasmas, viruses, and viroids are responsible for significant quantitative and qualitative losses in agricultural and horticultural crops. To effectively manage crop diseases, it is crucial to have a thorough understanding of the various aspects of these plant pathogens. This includes information on the precise identification of microbial plant pathogens, the process of disease development, epidemiology, assessment of losses due to diseases, principles of disease management, and their applications for containing the diseases. Additionally, information on possible ways of integrating these practices is necessary to develop and enhance the effectiveness of disease management systems suitable for different ecosystems. The basic plant pathological methods provided in the appendix and the glossary of plant pathological terms presented in this book will help students gain a clear understanding of the subject. This book will be useful for graduating students, researchers, and teachers who wish to update their knowledge on various aspects of microbial plant pathogens and the diseases they cause.