Excerpts from Steve
Tvedten's book "The Best Control
(Used here with permission.)
Intelligent Pest ManagementŪ Mound Treatments
Treating individual fire ant mounds is time consuming, but it is generally the most effective method of control. It takes from a few hours to a few weeks to kill the mound, depending on the product used. Individual mound treatment is usually most effective in the spring. The key is to locate and treat all the mounds in the area to be protected, not always a simple task. If many young mounds are missed, reinfestation of the area can take place in less than a year. The following discussions describe different ways to treat individual mounds.
Fire Ant Mound Drench. Follow directions for dilution of the Kleen KillŪ enzyme cleaners or soaps and gently flood the mound and surrounding area with the 3 oz. - 4 oz. per gallon of diluted Kleen KillŪ enzymes (or orange juice and water and a dash of dish soap). Then break open the top of the fire ant mound and pour 3 gallons of the diluted Kleen KillŪ enzyme/orange juice dilution directly into the galleries. It has been observed that when a man urinates on the mounds, the ants die, so try urine or a mix of turpentine and ammonia in water. Other drenches include Kleen KillŪ peppermint soap at a rate of 1 pint per 3 gallons of water. Open the top of the mound; then wet the top of the mound, then soak an area around the base of the mound and pour the remaining drench on the top of the mound from a height of at least 3 feet to help penetrate the entire mound.
Mound drenches are most effective after rains when the ground is wet and the ants have moved up into the drier soil in the mound. During excessively dry weather, effectiveness of the treatment may be enhanced if you soak the soil around the mound with plain water or diluted Kleen KillŪ enzymes before you flood the mound with diluted 3 gallons of Kleen KillŪ enzymes or orange juice, or steam. A simple way to flood a lot of mounds in your yard is to use a hose end sprayer and fill the container with Kleen KillŪ enzyme cleaner and/or Kleen KillŪ peppermint soap and then simply soak the mound and surrounding area.
Carbon Dioxide (CO2). Insert several pounds of dry ice or inject the dense gas which is one and a half times heavier than air (use a 20# cylinder of CO2 with 12 foot of hose and a 3 - 4 pipe attached) into the fire ant mound and it moves downward killing all worker ants, larvae and the queen. There is no odor or warning as the CO2 gas silently replaces the air in the entire chamber and any connecting tunnels or chambers or mounds. CO2 is not harmful to plants or lawns and after killing the fire ants in the mound, CO2 returns back into the air.
Carbon Monoxide (CO) created by burning charcoal briquettes will also control fire ants if you throw them into a hole in the mound with a 2+ wall (e.g., half of a barrel, open on both ends) around the mound/hole. Propane and other heavier than air gases will also work, but are certainly not as safe.
WAR: take two shovels, dust the handles, your shoes,
your socks, and trouser bottoms with talcum powder; get a shovel full of
each mound and transfer each shovel full to the another mound and let the
ants fight it out among themselves. (this method requires more
than one mound)
(Web Mistress Note: A little license was taken with title and some emphasis. However, the content is correct as it appears in "The Best Control (2nd Edition)