To kill those pesky fire ants use coffee grounds. Don't throw away those used coffee grounds after you perk that pot. Place in a plastic bag and save them. When you find a hill of ants in your yard place them on top and around the hill. Within a few hours the hill will be filled with dead ants.
If you don't drink enough coffee for coffee grounds then use Medina orange oil, about two ounces to a gallon of water over the mound. They are gone! I get the orange oil at Home Depot. Also good for fleas on a dog. About 1 ounce of water to a couple gallons of water. Put dog where you can pour it over him/her several times. I use a laundry basket/tub. To control fleas do it every couple weeks until all the eggs hatch. Also cleans the dog great.
Most coffee shops will be happy to give you their used grounds! My local store throws theirs into a seperate garbage bag for me to collect at the end of the day - my garden gets a boost while I stop this valuable resource heading to the tip. Most (not all) acid loving plants will love you for the coffee!