What is a causal agent of disease called?

A causal agent of disease is referred to as a pathogen. Pathogens are organisms, including bacteria, viruses, fungi, and nematodes, that can cause disease in plants, animals, and humans. In the context of plant health and arboriculture, recognizing pathogens is crucial for diagnosing diseases, understanding their mode of action, and implementing effective management practices.

For instance, a common pathogen responsible for tree diseases might be a specific type of fungus that infects the wood, leading to decay. By identifying the pathogen, arborists can take appropriate measures to control its spread, whether through chemical treatments, cultural practices, or selecting resistant plant varieties. This understanding plays a vital role in maintaining the health of trees and the overall ecosystem.

The other options relate to different concepts in disease transmission and ecological roles, but they do not specifically denote the causative agents of disease. A "carrier" refers to an organism that harbors a pathogen without necessarily showing signs of disease, while a "vector" is usually an organism that transmits a pathogen from one host to another. A "saprophyte" is an organism that feeds on dead or decaying organic matter, which is not responsible for causing disease in living hosts. Thus, understanding the role of