If you have a nest in the ground you can fill it with CO2 gas at the entrance hole in the evening when they are resting. The gas will sink into the nest and lea

If you have a nest in the ground you can fill it with CO2 gas at the entrance hole in the evening when they are resting. The gas will sink into the nest and leave no toxic residue. Trick might be finding the CO2, you can normally rent a tank at a welding supply shop. You'll also need a pressure regulator and hose. Dry ice can also be used, put some in a soda bottle with water and a hose taped up or snug fit to the top. Do not allow the bottle to pressurize however. Some people have reported using car exhaust but I'm not sure that's as effective.