Treating fire ant colonies in the fall can help edge out future colonies, according to Dan Suiter, a Cooperative Extension entomologist with the College of Agricultural and Environmental Sciences.
“Fire ant colonies have been growing through the summer and have reached their peak size,” he said. “Attacking those colonies now will help next spring when they start to swarm again.”
Fire ants are easier to kill in the fall for four main reasons. First, they’re more active. That makes it easier to treat them with fire ant baits. Fire ants are most active in spring and fall, when daytime temperatures are between 70 and 85 degrees, he said. Actively foraging ants will pick up bait and carry it into the nest within the first hour or two.
Second, 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. Third, in the fall, you’re treating when many fire ant colonies are very young. These colonies are well-established but still fairly small.
Fourth, and the one thing that makes fall the single best time to treat fire ants, according to Suiter, is that it’s followed by winter. Extreme cold is tough on fire ants. This makes baits even more effective in the fall.