Fly Spray – Don’t Forget to Shake, Shake, Shake!

fly spray or surface spray - pest control at home

Have you ever sprayed a fly with fly spray – and it just wouldn’t die?

Or worse still – it hit the ground, but by the time you came around to read its last rights at the rubbish bin it had vanished?

Well I was subject to this frustration only a couple of days ago – the worst thing was that I knew why it was happening, but having faith (and not much else), I persisted in trying to kill the mortal enemy buzzing around my home.

What’s going on?

Why is it that flies don’t always die when you know you’ve sprayed them mid-air!

The answer lies in the mixture of ingredients in the can – especially when the can gets emptier.

Back in a previous post I spoke about the difference between Surface Spray and Fly Spray.
You can jog your memory here if you missed the article…

Flying insect sprays use products that are extremely short lived in the environment and are metabolised (a big word for “broken down”) by the insect very quickly as well.

Sometimes these products are broken down by the insects systems faster than required for them to get a lethal dose.

To make this whole thing work better, most  flying insect sprays contain a “synergist” which is designed to prolong the effect of the chemical on the target insect so that its works long enough to ‘whack’ the insect.


The synergist and the chemical that does the killing don’t always stay mixed. They separate in the can.


Shake, Shake, Shake WELL before using – Every Time! This will combine the chemicals properly before use.

This is normally the first sentence in the Directions for Use section on the spray can.


Who actually reads “Directions for Use”?


Please read them from now on – you’d be surprised what you can learn, and what you shouldn’t have been doing with a product!

What happens if you don’t “Shake” the can?

In most cases the real chemical is used in the can first – leaving mostly the synergist behind.

By the end of the can you either have:

  • lots of synergist (which has little or no toxic effect at all), or
  • lots of the chemical – but the synergist is gone, so the fly recovers.

In the meantime…

  • What experiences have you had with pest control at home?

  • Have you ever wondered about pests that really annoy you?

I’d love to hear from you…

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  1. What Can I Do About Fruit Flies? | Pest Contol Help and Advice - February 20, 2013

    […] … and if you use fly spray – don’t forget to Shake the Can! You can jog your memory here if you missed the article… […]

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