Texas A&M has always recommended a two step program for fire ants. The first step is to broadcast a bait once or twice a year. I believe Amdro is the oldest, best known, and most available, although I used Logic from an ag chemical place. It was a yellow cornmeal impregnated with the poison and it was spread at the rate of one pound per acre. It does take several days, if not a week or more, for baits to work. The second step is a drench, as I mentioned; a liquid poured very slowly on the mound to disturb it as little as possible and let it run down into the tunnels.