What is the definition of a plant disease?

The definition of a plant disease is best characterized by the concept of abnormal physiological processes that result from the action of a causal pathogen. This includes fungi, bacteria, viruses, nematodes, and other organisms that can disrupt the normal functioning of the plant. A plant disease typically manifests as symptoms that reflect the underlying physiological changes caused by these pathogens, which may include wilting, discoloration, and stunted growth.

While abnormal growth due to environmental factors, loss of yield from poor farming practices, and weather effects on plant health are significant issues that can affect plants, they do not specifically meet the definition of a plant disease. Environmental factors may induce stress in plants but do not necessarily involve pathogens. Poor farming practices can lead to issues like nutrient deficiencies or pests, which again do not center on pathogenic causes. Weather can influence plant health but does not represent a disease caused by a pathogen. Thus, the essence of a plant disease is rooted in the interaction between the plant and a specific infectious agent, which is accurately captured by the chosen definition.