In a pump up sprayer mix 1 cup of your favorite concentrated insect spray, 1/4 cup of dish detergent, 1 cup of diesel fuel, and a gallon of water. Wait until it is dark and they are all in for the night, pump up the sprayer, shove the wand as far down the hole as you can, empty the sprayer and mash the hole closed. I have done this on several nests and never had them dig out.