Which term describes the process of a plant pathogen being carried by external means?

The term that accurately describes the process of a plant pathogen being carried by external means is "vector transfer." Vector transfer refers to the process where pathogens are transmitted from one host to another through external agents, such as insects, water, or wind.

Passive movement specifically involves the unintentional spread of pathogens, often through environmental factors like rain or soil movement, rather than through a living carrier, which is what vector transfer entails. Active movement would imply that the pathogen is being actively moved or driven by some force or organism, which does not capture the essence of the passive nature of many pathogen transmissions. Direct contact suggests that two organisms come into contact with each other, which does not represent the broader range of external means through which pathogens can be transferred.

In this context, vector transfer is the most accurate term, as it encapsulates the involvement of an intermediary agent that facilitates the spread of pathogens from one plant to another, emphasizing its significance in plant disease epidemiology.