Plant disease, an impairment of the normal state of a plant that interrupts or modifies its vital functions. They are normal part of nature and one of many ecological factors that help keep the hundreds of thousands of living plants and animals in balance with one another. Plant diseases have caused severe losses to humans in several ways. The goal of plant disease management is to reduce the economic and aesthetic damage caused by plant diseases. Successful disease control requires thorough knowledge of the causal agent and the disease cycle, host-pathogen interactions in relation to environmental factors, and cost.