Associate Certified Entomologist (ACE) Practice Exam

What is the mechanism of action for pyrethrins?

1. They interfere with hormonal balance in insects

2. They affect sodium channels in nerve axons

3. They increase digestive toxicity

4. They block water absorption

The correct answer is: They affect sodium channels in nerve axons

Pyrethrins act primarily by affecting sodium channels in nerve axons. They target the voltage-gated sodium channels that are crucial for generating and propagating electrical signals in neurons. When pyrethrins bind to these channels, they can cause prolonged openings or disruptions in the normal functioning of these channels, which leads to hyperexcitation of the nervous system. This hyperexcitation results in the neurological symptoms commonly observed in insects exposed to pyrethrins, ultimately leading to paralysis and death. This mechanism of action is well-established and is a key feature that differentiates pyrethrins from other classes of insecticides.