The American Phytopathological Society (APS) is an international scientific organization devoted to the study of plant diseases (phytopathology). APS promotes the advancement of modern concepts in the science of plant pathology and in plant health management in agricultural, urban and forest settings. The Society has nearly 5,000 plant pathologists and scientists worldwide. It is the oldest and largest organization of its type in the world. It is also a member of the International Society for Plant Pathology.