We used to get lots of wasp nests and one hornet's nest under the eaves of our house. Sprayed Diazinon under the eaves one year and had no more nests until the house got painted 3 or 4 years later.
Diazinon worked so well it got outlawed, but there are other products out there that might work as well. Just look for insecticides that are toxic to bees and it will do in any of the related stinging insects.