Mode of action

Definition

The functional or anatomical change in a living organism resulting from exposure to a substance, describing the physiological outcome rather than the molecular pathway. In entomology and pest management, the term distinguishes observable organism-level effects—such as paralysis, feeding cessation, or developmental disruption—from the underlying biochemical interactions. Mode of action classification is essential for insecticide resistance management, as rotating or mixing compounds with different modes of action delays the evolution of resistance.

Etymology

Example

Pyrethroid insecticides share the mode of action of rapid paralysis (excito-repellency and knockdown) due to sustained sodium channel activation, whereas neonicotinoids produce a distinct mode of action characterized by trembling, impaired coordination, and eventual lethargy from nicotinic acetylcholine receptor overstimulation.

Synonyms

• MoA

Related Terms

• mechanism of action
• insecticide resistance
• target-site resistance
• metabolic resistance
• IRAC classification
• toxicology
• pharmacodynamics

Usage Notes

Distinguished from 'mechanism of action,' which specifies molecular-level interactions (e.g., binding to a specific receptor or enzyme inhibition). In practice, entomologists and resistance managers often use 'mode of action' more broadly than pharmacologists, sometimes conflating it with mechanism; the Insecticide Resistance Action Committee (IRAC) groups compounds by mode of action for stewardship purposes. When describing resistance, specify whether the change affects the mode of action (physiological response) or mechanism (molecular target).