[theDentist]

Seems to me a fire solves many of them, but the underground ones... How about a huge container of pressurized FREON and a large hose?

[magslinger]

Some wasp and hornet spray down the hole, and then block the entrance seemed to work well.

You might want to do something about their food supplies, as well. Our neighbors haven't been putting up the humming bird feeder, and we haven't had as big a problem this year.