Healthy plants and trees are critical for sustainable and lucrative crop production as well as for ensuring the supply of fiber, food and fuel for a country. Ensuring plant and tree health involves protecting them from plant pathogens and pests using scientific and regulatory frameworks. Forest pathology refers to the study of diseases of woody plants across tree nurseries, natural forests, urban environments and planted landscapes. It is a branch of forestry that serves the needs of the environment and the general public by using scientific principles for the control and prevention of tree diseases. It is important to maintain effective plant health for increasing sustainability, productivity, resilience and profitability of agrifood systems. This book aims to shed light on some of the unexplored aspects of forest pathology and plant health, and the recent researches in this area of study. It will serve as a valuable source of reference for graduate and postgraduate students.