I think that leaving a shop vac on for awhile is a much better
alternative to pesticides!
 
Many years ago, a friend of mine had to remove a ground hornet nest. He
tried all of the common pesticides, as well as pouring gasoline down the
several exit holes, and setting it ablaze. Nothing much happened except
the hornets getting angrier.
 
Finally, he hooked up a 35 gallon shop vac to a 30' long piece of 3"
pipe, covered all but 1 of the holes with fresh cement, and arranged the
pipe so that it was within a few inches of the last exit. He also stuck a
pound of rotenone in the shop vac. He left the vac on for 2 weeks!
 
Imagine the sight of 35 gallons of dried and compressed hornets! That's
what we saw when we finally looked inside, after listening with
stethoscopes to make sure that they weren't alive inside. A pretty awsome
site!
 
Casey Burns