ABSTRACT
Before studying a plant disease, a framework or concept of what a plant disease is and, almost as importantly, what it is not, is essential. There are many definitions of plant disease. However, for this book, the following definition is used: A disease is the result of a dynamic, detrimental relationship between an organism that parasitizes or interferes with the normal processes of cells or tissues, or both, of the plant. The organism that incites or causes the disease process with the host is called a pathogen.
