Phytopathology or Plant Pathology is an interdisciplinary science that includes knowledge of botany, microbiology, crop science, soil science, ecology, genetics, biochemistry, molecular biology, and physiology. Phytopathology deals with the study and research on plant diseases that are caused by living organisms known as pathogens such as fungi, bacteria, viruses, nematodes, phytoplasmas, protozoa, and parasitic plants; and by nonliving agents, such as air pollutants, nutrient imbalances, and various environmental factors. Development of new and innovative ways to control plant diseases is a constant challenge for phytopathologists or plant pathologists. Plant diseases may be managed by altering the host plant, the pathogen, and or the environment. Examples include growing resistant plant varieties, planting pathogen-free seed or stock, applying a biological control agent, modifying environmental conditions to decrease disease, and using plant medicines that inhibit or kill the pathogen without harming the plant or the environment.