The present book discusses the biosynthesis and characterization of silver nanoparticles and evaluation of their antimicrobial activities against plant pathogens. The field of nanotechnology is one of the most active areas of research in modern materials science having diverse application in various fields. Nanotechnology is gaining tremendous impetus in the present century due to its capability of modulating metals into their nanosize, which drastically changes the chemical, physical and optical properties of material. Plant pathogens and pests are of the major factors limiting crop productivity. In recent years, Nanotechnology has been extensively applied for development of novel antimicrobials for the management of pathogenic micro-organisms affecting agricultural crops and other living forms. Among the different types of nanoparticles, Silver Nanoparticles have been used as effective biocides against a variety of plant pathogens. The strength of the book is extensive review and literature citations to give a snapshot of state of art research in synthesis of metallic nanoparticles using biological agents and their role in diverse applications.