Now that you know where the nest is, go out at night with a jar of about 8 ounces of gasoline. Quickly pour the gas on the nest and walk quickly away. Don't ignite the gas, the fumes will kill them. Best if it's cool, below 50 degrees because they are sluggish at those temps and you are safer from attack. If it doesn't cool off at night, just do it when it's coolest.
The problem is, I don't know where the nest is - or if there even is a nest. The were flying around under several pine trees in the front yard, probably four or five hundred square feet of area.
Keith