Importance Term. Plant pathology. The branch of botany that deal with nature,development,control of plant diseases. Plant pathologist. Person who specialize in study of plant disease. Disease. particular obnormal condition that effect negatively on structure and function of all or part of host.But it will not be immidiate external injury. Types of disease. 1-Systemic Disease. Whole body effect. 2-Localized Disease. Parts of body. Pathogen. Pathogen that generate disease. Pathogensis. It is a process or chain of events of disease development. Pathoginecity. It is an ability of pathogen to cause disease. Causal Complex. It is a envirnment factor of. Optimum temperture. Optimum humidity. Optimum light. Hyper Sensitivity. A hypersensitivity reaction is an unnecessary immune response that the body has to an antigen. Host. An organism an which disease takes place. Types of host. 1-Resistant Host. Host resistance is defined as the host abality to limit pathogen burden. 2-Suscepible host. It is a host that is severy attack by pathogin. 3-Immune Host. Host immune responses are considered to be critical in controlling the infection.Both durning primary infection and in the carrier state. Resistance. It is a abality of host which posseses the qualities that hinder completely or partialy development of disease. Susceptibility. The condition of host that makes it suitable for attack by pathogen. Immunity. Abality of host to resistance against given pathogen even under optimum condition. Klenducity. Tedency of host to escape from disease is called klenducity.