Is it true that you have to change an insect poison all the time because insects get used to the smell?

Question

Is it true that you have to change an insect poison all the time because insects get used to the smell?

Answer 1

It's not the smell that kills them! If they got used to the smell that would make it more dangerous to them.

Insects do sometimes become resistant to insecticides (natural selection in action). Changing to an insecticide with a different poison will kill off the ones that are resistant to the first one. This is in the large-scale use of insecticides of course, not spraying flies in your house!

Answer 2

The smell has nothing to do with it. Insects can get resistant to the poison if it is used continuously. If a few are poisoned, but it is not enough to kill them, they will overcome the poison and be more resistant to it the next time, meaning they will be harder to kill. By changing poisons, they will have to adapt again, and this stress is hard on them, meaning they will be weakened and more susceptible to the poison.