Boiling water!
I've got a friend who is a chemist with Johnson & Johnson, and that's what he reccomends. Pierce the mound, like you've been doing, and flood it with boiling water, really saturate it. I've used a bait which really works, but I don't remember the brand name. It's at the farm, and I won't be there until Friday. It's used by breaking the mound open, sprinkling in a liberal amount of the poison, and flooding with water, but not necessarily hot. The mounds on my farm grow to 2 feet tall or more, sometimes!
Jerry
