Plant pathology is a branch of agricultural science which deals with plant diseases and their management. Diseases in plants caused by the pathogens which are microorganisms but not all the microorganisms are pathogens. The microorganisms which are causing diseases in plants are called as pathogens. They may be fungi or bacteria or virus or phytoplasma or viroids, or spiroplasma or virusoids. To reduce the yield loss in crops caused by the pathogens, a strong knowledge is essential about the causes and their management methodologies. This book mainly deals about plant pathogens, their symptoms and the principles involved in the management of plant diseases. It will be useful to the under graduate, post graduate students and the people who are involved in crop management.