Which term best describes an invasion of a plant by a pathogen?

The term "infection" specifically refers to the process by which a pathogen invades and establishes itself within a plant. When a pathogen, such as a fungus, bacterium, or virus, enters the plant tissue, it disrupts normal physiological functions, often leading to disease. This process encompasses not only the initial entry of the pathogen but also its development and multiplication within the host, ultimately causing harm.

In this context, other terms do not encapsulate the same specific interaction. For example, "inoculation" typically refers to the act of introducing a pathogen or its spores to a plant to study disease or for controlled infection, rather than the actual invasion process. "Infestation" usually pertains to the presence of pests like insects or mites, which can sometimes be confused with pathogens, but fundamentally describes a different type of host disruption. "Intrusion," while hinting at an unwelcome entry, lacks the specificity of the biological interaction that "infection" conveys in the context of plant pathology. Therefore, "infection" accurately describes the phenomenon of a pathogen invading a plant and causing damage.