This book provides comprehensive knowledge of the methods of detection and identification of phyllosphere microbial pathogens and the management of different kinds of diseases caused by them in various crops. Interactions between pathogens and host plants result in the induction of defense responses expressed via molecular signals, from initiation of infection to systemic progression of pathogen invasion in susceptible plants and contrasting signals in resistant plants, leading to inhibition of pathogen development through activation of preinfectional and postinfectional defense responses. These are critically discussed. The author describes the intricate and complex competitive activities of the pathogens and host plants in a molecular warfare that the host plant must win to break the link in the pathogens' life cycle, allowing the development of disease management strategies based on the principles of exclusion, eradication, and immunization. Integration of strategies concerning the development of cultivars resistant to pathogens through breeding and biotechnological techniques, application of biotic and abiotic inducers of resistance to pathogens, and use of disease-free seeds and propagules that are complementary to each other along with effective cultural practices are emphasized. This book presents information gathered through an extensive literature search to help researchers and graduate students in agricultural sciences identify research gaps and successfully complete their research projects.