I'm a live and let live kind of person. Until now.
Yellow jackets have taken up residence in one of my flower beds at the base of (under) my 17yo Japanese Maple. Pulling weeds, and I grabbed a vine that apparently woke everybody up. I got 18 stings before I could get away.
There isn't enough witch hazel in the world to stop those stings. Double dosed on Benadryl and used an entire tube of lanacaine creme and they still hurt. Swelling was awful, one sting was the size of a golfball. Yellow Jackets can have the 200 acres surrounding me on all sides that my neighbors have left to run wild, but they can't have around the house. If one of my puppies had that many stings, it could have killed him. These guys have to go.
Old timers are telling me to get rid of the nest -- wait till dusk when they are sleeping and pour the hole full of kerosene and light it up. I'm over "good will towards all" and will do what it takes. Problem is the Japanese Maple that I am (used to be very) fond of.
You could always call a professional to deal with them, they probably have better methods as well as protective gear to do the job without getting hurt. If you try to do something yourself though I would definitely wait until dusk when they're all back in the nest, any other time when they're active you're more likely to get stung. There are probably solutions other than kerosene though--if you know exactly where their hole is I wonder if you could just blast it with wasp spray a couple nights in a row or something? Never tried it though, just guessing. ( I used to get them in my yard now and then but the nests were always in an out of the way enough area that I didn't mess with them. They won't build a nest in the same place the following year so I was able to wait them out)
Haven't done this myself, but I've read that a good solution if you don't want to go the professional route is to - as previously said- wait until after dusk, and sprinkle the ground around the hole with Sevin, pour some down into the hole, and quickly invert a glass bowl over the hole. If the ground is uneven, put rags around the lip so none can escape, and keep it there. The next day when they wake up, if they make it out of the hole, they'll return to the nest with poison on their bodies when they can't get past the bowl. It should wipe out the nest. Good luck!
You can pour kerosene, or gasoline for that matter, down the hole and kill the hive, no need to ignite it. Or spray the hole with poison, as ecrane3 suggested. My wife recently found a spray that creates a foam to fill the hole which I used recently for a yellow jacket nest in our front yard. As long as you wait till dusk you will kill them all but if you were to spray the nest at another time you'll still kill the nest and it would just take a little time for the survivors to figure it out and leave the area.
I just realized you may have already taken action. I would expect the seven dust to work also. Hope it did.