Fire Ant Control in the Fall
When you think of fire ants in the fall, "vulnerable" isn't the first word that pops into your mind. But it should be.
If you are going to treat fire ants only once a year, do it in the fall. Fire ants are easier to kill in the fall, for four main reasons:
2. In the cooler weather of fall, fire ants aren't too deep in the ground. That makes them easier to kill with a mound-drench, granular, dust or aerosol contact insecticide. When you use those products, it's critical to treat when the queen and brood are close to the surface.
3. The one thing that makes fall the single best time to treat fire ants is that it's followed by winter. Extreme cold is tough on fire ants. That makes baits even more effective in the fall. Baits take a long time to work. They weaken colonies and make them less able to respond to the challenges of winter weather. The young colonies are especially vulnerable because they don't have many workers. So they can't respond very quickly to the need to escape freezing temperatures. The networked tunnels of a fire ant mound are constantly collapsing. Moving deeper into the ground requires a lot of work. Anything you can do to reduce the number of ants available to gather food and maintain the mound structure makes the colony less able to survive winter weather.
Source: Dan Suiter, Cooperative Extension entomologist, University of Georgia College of Agricultural and Environmental Sciences
Fire Ant Killer