Fall is the best time to treat fire ants to destroy mounds

Last week I was playing golf at a course near Augusta and noticed how bad the fire ants were. The mounds were everywhere. Early on in our tournament, one of my fellow players had to come out of his shoes twice, so after his painful experiences he became more diligent in watching where he stood.


There are a couple of reasons why fire ants have been so bad the last couple of weeks. One, when the weather cools down, the fire ants become more active. Like us, they don’t like the hot summer weather. Fire ants are most active in the fall when the daytime temperatures are between 70 and 85 degrees. The rain also gets them excited and drives them out of the ground as they build the mounds higher to get away from excess moisture.

Active fire ants make October a great month to treat and kill them. There are many fire ant-control products available at garden centers, but perhaps the best is a fire ant bait.

Fire ant baits contain pesticides on processed corn grits coated with soybean oil. Several baits are on the market but we are limited on the ones we can purchase in the Augusta area. The most common one you’ll see is Amdro. Others are Award, Ascend, Extinguish, Spectracide Fire Ant Bait, and Pennington Fire Ant Bait. Amdro even has one in a more user-friendly mixture that is designed to be applied for sa ubdivision-size yard.

Treat your yard late in the day when it is dry and rain is not forecast for at least 24 hours after you apply the bait. After the bait is on the ground, actively foraging ants will quickly pick up and carry it into the nest within minutes. If the ants are inactive and don’t find the bait quickly, it will become rancid. By the time the ants find it, it no longer appeals to them.

Fire ants are also vulnerable to insecticides in the cooler weather in the fall because their mounds are not very deep in the ground. That makes them easier to kill with a mound drench, granular, dust, or aerosol contact insecticide. It’s critical to treat when the queen and brood (eggs, larvae and pupae) are close to the surface.

Another advantage unique to the fall is that you are treating when many of the fire ant colonies in your yard are very young. Fire ants mate almost year-round except for two or three winter months, but they’re most actively mating in the spring. The mated queens fly off and establish new colonies. By the time fall rolls around, these colonies are well established but still very small. Quite often you don’t even know they’re there unless we get a lot of rain to bring the mound up and out of the ground. If you don’t treat them, they will become big mounds by next year.

Use fresh bait, and apply it by label directions. It doesn’t take much. Usually about 1 to 1½ pounds per acre is sufficient. Baits should eliminate about 80-95 percent of fire ant mounds.

Another big thing that makes fall the single best time to treat fire ants with baits is that it is followed by winter. Cold weather is tough on fire ants. Baits take a few weeks to work, but 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 worker ants. So they cannot respond very quickly to the need to escape freezing temperatures.

The network of tunnels of a fire ant mound is 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 makes the colony less able to survive winter weather.

Baits are by far the most economical option if you have a large yard of perhaps an acre or more.

Many brands of baits fall into two basic groups; those with active ingredients that are toxic to ants (Amdro) and those that have as active ingredients growth regulators that sterilize the queen and stop development of the immature ants in the colony.

Applied every six months, they often carry a guarantee of “no mounds” if applied correctly. It’s not “no ants” but “no mounds.” It takes about six months for a colony of ants to grow from the founding queen to a size where there are enough workers to build the characteristic mound. Baits are good at breaking that cycle. There will be ants between these applications, just not all that many.

For smaller areas, or where you need zero ants, use a broadcast application of a contact insecticide. Examples are those with pyrethroids as active ingredients. Pyrethroids are active ingredients ending in “thrin” such as bifenthrin, permethrin, cypermethrin, or cyfluthrin.

Pyrethroids will provide one to four months of control. After that, the cycle starts over when the ants start flying, which is basically almost year round except for two or three winter months.

Another insecticide that has only been on the market for about five to six years is indoxacarb, sold as Advion for commercial use and in the Spectracide line (Once & Done) for homeowners. It’s a bait, but instead of weeks to see a reduction in ants, they start to disappear in a couple of days. It’s still a “no mounds” type, but fast.