We have a big problem with fire ants aka candelilla here in Panama. After some reading and experimentation, I found a super easy way to deal with them. Boiling water kills them, and coffee repels them. So, here is my process:

1. I make coffee in the morning, and drink it. <3
2. I take the coffee grounds, and place them around my plants, and other areas I want to protect from the ants.
3. without cleaning the coffee pot I boil more water in it. This water still has lots of oils and chemicals from the coffee residue.
4. Pour the boiling coffee / water onto the ant nests.
5. Repeat 3 & 4 until the ant nest is all saturated and dead.

The boiling water does also kill any plants that are hit with it, but does no permanent damage, and leaves no chemical residue.