You can help stop wasps
The best way to reduce a local wasp population is to find and destroy all the nests in the area. Usually wasps fly no further than 200 metres, so you should aim to kill all the nests within this range.
How to find nests
If you search on sunny days, near dawn or dusk, the low light angles will highlight the flight path as wasps enter and leave the nest. You can put out a bait of cat food sprinkled with flour which will make the wasps easier to see.
How to poison the nest
Place a dessertspoonful of insecticide at the nest entrance after dark when the wasps have stopped flying. You can use a puffer bottle for this job. Worker wasps flying in and out will spread the powder into the nest and the colony usually dies within a day. If activity continues repeat the treatment until wasp activity ceases.
Don't shine your torch into the nest or wasps will fly up the beam.
What poisons to use
There is a range of insecticides available from hardware and garden stores. These include Wasp Killer Dust and Permex Insect Dust, which have permethrin as the active ingredient, and Rentokil Wasp Killer and No Wasps Insecticidal Dust, which both use carbaryl. Follow the safety instructions supplied with the insecticide.