If anyone does run into problems with ground nests of stinging insects, forget chemicals. The solution is easy and cheap. A bucket of water with a good dose of liquid dish soap mixed in, and a shovel. Pour some onto the nest opening, then start breaking up the ground with the shovel, frequently pouring in more soapy water. The soap acts as a wetting agent, allowing the water to get into their breathing holes, drowning them in seconds.
This works well for above ground nests as well. A pump up sprayer with the same soapy water (stirred, not shaken!), locate the nest in the evening, and hose it down. They will fall to the ground in seconds and are dead within 1/2 a minute. I learned this 15 years ago watching a show on the African bees. The guy eradicated a nest using nothing but a back pack sprayer filled with soapy water.
Gary