The answer to 'how to kill fire ant' is to use a fire ant bait or granular insecticide specifically formulated for fire ant control. These products contain active ingredients like hydramethylnon or spinosad that are effective at eliminating fire ant colonies. Apply the bait or granules according to the product instructions, typically by spreading it around the mound or nest.
It's important to note that fire ant control requires persistence and repeated applications, as the colonies can be difficult to fully eliminate. You may need to reapply the treatment every 4-6 weeks during the active season to maintain control. Always wear protective gloves and follow all safety precautions when handling pesticides.