monocidal

Monocidal is an adjective used in biology and related fields to describe a lethal effect that targets a single organism, species, or genotype within a given context. The term is formed from mono- meaning one and -cidal derived from Latin caedere, “to kill.” Consequently, monocidal implies a lethality that is not general or broad-spectrum but restricted to a defined target.

Usage and scope: In ecology, microbiology, and pharmacology, monocidal is more often encountered as a theoretical or historical descriptor. In practice, scientists typically prefer more specific terms such as host-specific, narrow-spectrum, or selective lethality. In pharmacology, the standard descriptors are bactericidal, fungicidal, or virucidal when referring to killing pathogens; using monocidal to describe a single-target lethality is rare and can be ambiguous unless the target is explicitly defined.

Examples: A monocidal pathogen would be one that kills only individuals of a particular host species or genotype, rather than causing mortality across multiple species. A monocidal pesticide might be described in older literature as targeting a single pest species, though contemporary usage favors “targeted” or “selective” pesticides.

See also: selective toxicity; narrow-spectrum agents; host specificity; bactericidal; fungicidal; virucidal.