By David Saunders, BCE, Technical Specialist, Entomology and Regulatory Services, Terminix International Photographs courtesy of Terminix
Although fire ants are good predators in southern gardens by preying on pest species, their painful bites and stings are problematic for the gardener. Control can be quite a challenge. If your garden is to be pesticide-free, then one option is to dig up the mounds with a shovel and place it in a bucket of soapy water to drown them. Soap is the key ingredient, as fire ants found in flood prone areas merely hang on to one another during floods and raft to drier locations. To avoid drowning they rotate who is one top of the pile and gather a bubble of air around them when they go back under water like a miniature diving bell. The soap breaks down the water tension and suffocates the ants. This soapy water technique has worked well to control fire ants in the Panda exhibit at the Memphis Zoo, which is a pesticide-free zone.
If a liquid insecticidal drench is used on the mound, then volume is the key for control. An understanding of fire ant mound systems is crucial. The dirt mound is more like the tip of an iceberg. Fire ants have feeding and escape tunnels leading five feet from the dirt mound in all directions. This means the area of concern is more of a ten-foot diameter circle, not just the dirt pile.
Carefully pour the drench on the dirt mound, but then feather out a light application in a five-foot radius. Most homeowners just treat the dirt pile, and then complain the treatment just caused the ants to move over a few feet and did not control them. Just remember the 10-foot circle of treatment. Granular insecticide formulations are also a choice for treating the 10-foot circle, but must be watered in to activate the granules.
Fire ant baits are an option in the garden and would not put your beneficial insects at risk. Some baits are fast acting while others are fairly slow. The principle behind ant baiting is not very well understood by most. The worker ants take the bait back to the ant larvae and feed it to them, who in turn feed it to nurse ants, who then feed it eventually to the queens. Adult ants cannot take any solid foods, just liquids, hence feeding the larvae first, who convert it to a liquid. The queens, larvae and
nurse ants die from the bait and the other workers then must die from old age. Fire ant workers have an average life span of only about 6 weeks, so some baits may take up to 6 weeks for control. That is a lot slower than the drench, but preserves your beneficial predators and parasites of other garden pests.