I stuck a liquid propane hose in their hole from an old design fitting, gassed them for about 10 minutes,they where croaking as soon as they landed,the propane was brutal on them, poured some gas in, then touched the hole with a flame, let it die off and poured about 2 cups of gas in again after breaking up the earth with a spade. Some scouts returned the next day, but the nest was empty and bee free by nightfall. Not a sting. I did hover over their hole when it was active with the exmark ZTR, at 16,000 RPM blade tip....I am sure they where fired up.....kind of enjoyed it to tell ya truth.
I had 3 nest one year and my dog found them all.