Knockdown
- Pronunciation
- /NAHK-down/
- Category
- Physiology
- Singular
- knockdown
- Plural
- knockdowns
Definition
In insect toxicology and pest management, the rapid, reversible paralysis or immobilization of an following exposure to a neurotoxic , typically a . Knockdown precedes mortality and is measured as a distinct endpoint in ; individuals may later recover (knockdown recovery) or die depending on dose, temperature, and resistance mechanisms. The term distinguishes acute incapacitation from lethal effects and is quantified as the percentage of test insects unable to maintain coordinated movement or upright posture at a specified time after exposure (e.g., KD50 for knockdown time or KT50 for median knockdown time at a given concentration).
Etymology
From the verb phrase 'knock down,' describing the sudden collapse of motor function in poisoned insects.
Example
In a standard WHO tube test for mosquito susceptibility, a 1-hour exposure to 0.75% permethrin should achieve ≥95% knockdown of susceptible Anopheles gambiae within 60 minutes; failure to reach this threshold indicates possible knockdown resistance (kdr).
Synonyms
- KD
- paralysis (reversible)
- prostration
Related Terms
- knockdown resistance (kdr)
- knockdown time
- KT50
- KD50
- pyrethroid
- insecticide bioassay
- mortality
- recovery
- Neurotoxin
Usage Notes
Knockdown is strictly distinguished from mortality in toxicological protocols: an insect may be knocked down yet survive, or die without showing classic knockdown depending on the . The term is most commonly applied to fast-acting (, , some ) and is rarely used for slower-acting compounds like . In field applications, knockdown provides rapid suppression even when subsequent mortality is incomplete. Temperature strongly influences knockdown expression—cold conditions often prolong knockdown recovery in . The abbreviation KD (not to be confused with 'knockout' in genetics) is standard in literature.