It is possible to bait European wasps (with readily available products eg Permethrin, Fipronil – sold as ‘Frontline’) in such a way that it does not harm anything else (bees, birds). The wasps take the poison (from converted milk bottle traps) back to their nests and kill the nests. Every wasp for 200 metres will be eliminated. My view is that this should have been done by Government 30 years ago. Astonishingly in Victoria it is illegal to post instructions on how to do it on pain of a fine of $7500, though the Tasmanian Government has instructions on how to do it! You can try a Google Search (eg bait European wasps).
I bought one 2.68ml pipette of Frontine (large dog) from my local Safeway store for A$17 (April 2018). Diluted 100 times (268 mls) with water this was (or will be) enough to prepare 52 x 20 gram minced meat baits which I simply slipped into a used plastic milk bottle I had drilled a few 12mm holes in and hung in the garden after training the wasps for a couple of days with unbaited mince. That single purchase should kill very wasp within 200 metres of our property for several years!
There is a useful Facebook Group. Below are a couple of useful links
PS: I have been helping with some garden tidying (Read ‘blackberry slashing’) at my son’s new 10 acre property. I managed to stand on a nest of the blighters and they all went for me. I am here to tell you they sure can sting (dozens of times) and that the stings give you trouble for at least a week!