Managing Fire Ants

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Cary Sims
Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.

I had a phone call a couple of days ago from a gentleman that wanted to know how he could get rid of all the fire ants on his acreage.  ‘Acreage’ implied quite a large piece of real estate and an expense that could be very costly. I suggested that we just work on the areas around the house, garden, and barns and he seemed to agree with that idea.

Fire ants are native to South America. They entered the U.S. through Mobile, Alabama, probably in soil used for ships’ ballasts. They were accidentally introduced around the 1930’s and have been spreading since.

Red imported fire ants are very aggressive, efficient competitors. Since the 1950’s in Texas, the ant has been spreading north, west and south. They now infest the eastern two-thirds of the state, and most every urban area in west Texas. While the bad news is that they are a permanent problem, the good news is that, with relatively little cost and effort, you can prevent most of the problems they cause using currently available methods.

Fire ant colonies usually take the form of large dirt mounds. You can also find nests in rotting logs, around trees, under pavement, or under buildings. Fire ants can also set up home indoors, or (frustratingly) inside electrical equipment and utilities, which can certainly cause a short circuit at an inopportune time. Fire ant nests will not have a single nest entry, but rather, several entrances under the mound. When the nest is disturbed, many fire ants will swarm out to attack the intruder.

Fire ants are omnivorous. They eat plants, insects, oils, and sugars, but they are only able to ingest liquids. Larvae break down solid food into liquids for fire ants by regurgitating digestive enzymes onto the food. Some fancy terminology that I learned some years ago about fire ants are that they are “thermo regulatory“ and “hydro regulatory”. Thermo regulatory means they work to maintain a body at a particular temperature whatever its environmental temperature. Hence in the winter, you do not see many fire ant colonies above the ground, but during the warmer spring and summer months, we readily see their mounds above the surface of the ground.

Likewise with hydro regulation, they can tunnel deep into the ground to find water in times of drought and will build mounds above the soil to escape waterlogged soils. Indeed, they will often seem to go away when they are just deeper in the ground looking for moisture and more moderate temperatures.

But all most folks really want to know about fire ants is how to get rid of them.

Baits can be used over a large area or on individual mounds. Two common ingredients, hydramethylnon and sulfluramid, kill ants by preventing them from converting food into energy. Avermectin is derived from a soil fungus and inhibits nerve function. As a broadcast treatment it works like an insect growth regulator. While baits are effective, they are slow and may take several weeks.

There are several individual mound treatment options available on the market. Dusts, granules and drenches all have their place so long as you follow the instructions.

There are also some long-lasting residual insecticide treatments. With this tactic, a contact insecticide is applied to the lawn and landscape surface. This is more expensive than other control methods, but it may be more effective in smaller areas because ants that move into treated areas will be eliminated as long as the chemical is active. Granular products are best applied with a push-type fertilizer spreader and must be watered in after treatment. Faster-acting contact insecticides, such as the pyrethroids, eliminate ants on the surface for months but may not eliminate colonies nesting deeper in the soil.

If you wish to go the organic route, organic products that contain ingredients such as boric acid or diatomaceous earth can kill ants, but their effectiveness to kill whole colonies has not been consistently demonstrated.

Texas AgriLife encourages the “Texas Two-Step” method where you both treat individual colonies and then bait for long term residual control.  While this is best accomplished in the fall, I bet most folks will want them gone now and then are willing to retreat again in October.

Whatever you choose, always follow the label for whichever product you choose. There is a wealth of good information contained in the tiny print on the back of the package. Closely follow the label directions.

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