I've heard that MALATHION, two tablespoons per gallon of water does the trick. On carpenter bees too.

FireIsHot's method of saturating around the mound then giving them a dose from deep in the mound to the surface is probably a very good approach.

My personal approach is to run over the mounds with my mower, exchanging the wear on the blades for speedily dealing with the mounds.

As in using any insecticide, you would want to refer to the label to see if that use of Malathion is an approved use.