Question:medium
Effect of pyrethrum on mosquitoes is described as
Effect of pyrethrum on mosquitoes is described as
Show Hint
Pyrethrum is famous for causing fast, temporary insect paralysis, not for long lasting surface action.
Updated On: Jul 7, 2026
- Residual
- Repellent
- Knock down
- Contact
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Concept:
Pyrethrum comes from Chrysanthemum flowers and acts on the nerve membrane sodium channels of insects.
Step 2: Key Formula or Approach:
Because it keeps the sodium channels open too long, the insect's nerves fire again and again, and the insect becomes paralysed almost at once. Vector control books name this fast paralysis the knock down effect.
Step 3: Detailed Explanation:
This knock down effect is the defining, named property of pyrethrum. It is why pyrethrum sprays are chosen when a quick, visible drop of flying mosquitoes is wanted, for example during aircraft disinsection.
Residual action, staying active on walls for weeks, is instead the strong point of DDT, since pyrethrum degrades quickly in light and heat.
A repellent keeps insects from landing at all, which is a separate class of action seen with agents like DEET, not with pyrethrum.
Contact only tells us the entry route into the insect body, it does not name the special effect pyrethrum is famous for.
Step 4: Final Answer:
The effect of pyrethrum on mosquitoes is best described as the knock down effect. \[ \boxed{\text{Knock down effect}} \]
Pyrethrum comes from Chrysanthemum flowers and acts on the nerve membrane sodium channels of insects.
Step 2: Key Formula or Approach:
Because it keeps the sodium channels open too long, the insect's nerves fire again and again, and the insect becomes paralysed almost at once. Vector control books name this fast paralysis the knock down effect.
Step 3: Detailed Explanation:
This knock down effect is the defining, named property of pyrethrum. It is why pyrethrum sprays are chosen when a quick, visible drop of flying mosquitoes is wanted, for example during aircraft disinsection.
Residual action, staying active on walls for weeks, is instead the strong point of DDT, since pyrethrum degrades quickly in light and heat.
A repellent keeps insects from landing at all, which is a separate class of action seen with agents like DEET, not with pyrethrum.
Contact only tells us the entry route into the insect body, it does not name the special effect pyrethrum is famous for.
Step 4: Final Answer:
The effect of pyrethrum on mosquitoes is best described as the knock down effect. \[ \boxed{\text{Knock down effect}} \]
Was this answer helpful?
0
