put a little gasoline in a plastic bottle. 6 or 8 ounces is plenty. wait til right at dark, and watch them for a few minutes. they return to the nest before it gets too dark. when they start to thin out, just pour the gas into the hole. they won't boil out on you like they do in the daylight. usually you won't even really see one of them. it will wipe out the whole nest immediately. the fumes get them. it will kill a small bit of grass for a while, but they will be long gone. you can do the same thing with malathion also, but gas is cheaper! just wait til near dark, so you get most of them while they are in the nest.

good luck!