Kill Wasps with a Natural, Non-Toxic, 3 Ingredient Spray!
20 - 30 Drops Eucalyptus Essential Oil
20 - 30 Drops Peppermint Essential Oil
1/4 - 1/2 cup Dawn Dish Soap (HAS to be the blue kind)
Add the above ingredients to an empty spray bottle (anything around 500mL - 1litre is good), measurements do not have to be exact. Just eyeball it, and it'll work. Then add water SLOWLY (or it will bubble like mad) until it's around 3/4 full. give a good shake and start spraying!
I have found that the more concentrated your solution is, the quicker the wasp dies, HOWEVER, it's also more harsh on plants and surfaces, so don't over-do it!
So, I'm no wasp expert, but I love to know why something works. With a bit of research, I've learned that the dish soap helps to compromise the wasps coating on its exoskeleton. The peppermint and eucalyptus essential oils are both neurotoxic and the wasp is almost instantly killed. If this is true, it explains why the wasps die so quickly, and aren't able to fly away.
So, go forth and keep those darn wasps out of your indoor spaces!