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Treat fire ants in the fall to reduce spring populations

As summer wanes and autumn falls into the forefront we begin adjusting to the change in season. Pumpkin spice flavored coffees and treats abound, seasonal décor finds its way into our homes, and with the first hint of cooler weather we pull out our fall attire. One might even say that there is an instinctual factor at play here. In our own way, we’re preparing for winter.

Other members of the biological community sense this change too. Late September is a UGA significant time of year for migratory birds. On September 22, the Georgia Audubon Society announced on that night along an estimated 31.6 million birds would be migrating over Georgia. Mammalian activity also begins to spike during this time. But, it’s not just birds and mammals that are responding to the change in season – insects have an instinct to survive the winter months as well. 

Fire ants have a two-node petiole, a ten-segmented antenna with a two-segmented club, and a stinger. Image credit: Eli Sarnat, PIAkey: Invasive Ants of the Pacific Islands, USDA APHIS PPQ, Bugwood.org

For example, imported red fire ants are more active in the fall. During this period food resources are becoming scarce so foraging workers are more likely to pick up insecticide baits. With this in mind, fall is an excellent time to interrupt the winter preparations of this insect. Fire ants do not survive the cold well and colonies with depressed populations may not be able to survive the winter. Treating ants now reduces their numbers and their chances of winter survival.

There are two basic chemical control options for fire ants: individual mound treatments and broadcasting. In general, individual mound treatments use less insecticide and reduce the amount of active ingredient used in an area compared to broadcast treatments. Liquid or dust formulations are available. Another benefit to this approach is that it reduces the impact on non-target insects’ ground-dwelling insects.

When selecting a product, be certain to check the label to ensure the product you intend to use is labeled for use in the area where you have the infestation. For example, many fire ant baits and products are not labeled for use in areas with edible food crops or around livestock and poultry. It is critical that you read the product label and make sure it is safe to use in the area of concern. Always refer to the pesticide label and follow the directions accordingly. If you need help selecting a product, contact the Extension office for assistance.

As far as how to correctly apply a liquid drench treatment, the objective is to completely saturate the individual mounds so the insecticide will contact most of the fire ants in the colony. Drenches are fast-acting and usually the preferred treatment method when the risk of human contact with fire ants is high and the infestation must be eliminated quickly. Areas of concern that may warrant immediate mound elimination include high-traffic areas, such as home grounds, schools and child care facilities, public parks, etc. Best results are observed in spring and fall because temperatures average between 70 and 85°F. This is the preferred temperature for fire ants, so they will be closer to the soil surface during these times of year. 

While individual mound treatments are sometimes warranted and are fast-acting, baits are also an option. The concept behind a bait is that we are taking advantage of the insects foraging instincts by offering them a mixture of an insecticide disguised as a food that is attractive to fire ants. Foraging worker ants find the bait particles, confuse them as a food source, and then carry the bait back to the mound and feed them to the colony’s brood and queen. Since the ultimate goal is to eliminate the queen so the colony will collapse, baits are a highly desirable and effective fire any treatment. Though, it may take a several weeks for all of the worker ants to die off.

The active ingredients in ant baits are rapidly degraded by high temperature, high humidity, and intense sunlight, so it is always important to use fresh bait each year and to store it properly. Remember, the whole reason the ants are collecting the bait and taking it back to the colony is because they find it as a desirable food source, so you want the bait to be fresh and in good condition. Another consideration is that you want the ants to be actively foraging when you put the bait out. A simple test to ensure the ants are active is to take some greasy potato chips and toss them out into the yard. After an hour, if ants have discovered the chips, then you know that the activity is strong that day and the ants will likely find your bait. Just like with the mound drenched, you will need to apply the bait according to label directions. Generally, it is best to sprinkle the amount recommended on the label around the mound, not on top of the mound. Be mindful of the current and future weather conditions, most products recommend the bait not be applied within 6 hours after rainfall. If you have outdoor pets, bring them in the day you treat the yard.