I have small yellow jackets, in a dry stacked block wall. I tried spraying inside the hole but it didn't kill them. Would I beable to remove the blocks at night without making them mad?

It isn't the night time, it's cool temperature that slows them down and they can't fly. So you either find a way to get rid of them in the day time or wait until fall. If you can throw a heavy tarp over the whole wall and set off a bomb under it (a spray can with a clip that holds the button down), that might do it.

You might be able to sneak up on them at night, but you risk getting stung. Didn't they get "mad" when you sprayed insecticide in their nest? How did you get so close without getting stung?

The insecticide you used, might not have been strong enough or you haven't waited long enough. It sounds like you put a brick at their entrance. If you trapped the yellow jackets inside and they don't find their way out of another hole, the yellow jackets might die after a day or two. But unless you can hear them or see them flying how will you know you killed them? If they aren't finding their way out; because you have imprisoned them in the wall, they will eventually die.

It is best to spray yellowjacket nests (or remove blocks) at night, after they return to their nest . There are aerosol insecticides designed just for wasps and yellowjackets. These insecticides shoot a stream so that you can stand back from the nest entrance hole. Get the product that provides a quick knock down. Wear gloves and a bee veil for safety or be prepared to run.

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