Managing those pesky, unwanted fire ants

Robert Nunnally/FlickrA fire ant mounds can be managed with the right treatment plan.

If you work or play outdoors on a regular basis, chances are you have come in contact with fire ants. I would guess that contact was not a positive experience. A friend of mine describes fire ants as treacherous, combative and rude. I did not argue with his description. Fire ants can be found in open spaces, next to buildings or trees and even in electrical boxes. Ranchers and farmers despise them because they damage mowers, and other agriculture equipment. The fire ant mounds in pastures makes it a challenge to bale hay. The grass will not cut evenly and the ants get into the bales. Picking up a square bale with ants in it is not a fun task. Texas A&M says that fire ants are also a financial problem, and they cause up to $6 billion a year, including the cost of pesticides. 

The question is, of course, what can we do to manage them? Manage them is the correct phrase to use because it is next to impossible to get rid of them completely. With that thought in mind, Texas A&M has come up with a good plan that has been researched and field tested. You will not wipe them out completely, but you should reduce their population significantly.

The Texas Two-Step Method

Step 1 — Broadcast a fire ant bait once or twice a year to reduce the fire ant colonies. The goal is to reduce the colonies by 80 to 90 percent. That would be a fantastic start.

Step 2 — Treat mounds that you did not get with Step 1 and colonies that move into the bait-treated areas. During field tests, Step 2 was not always necessary.

The Texas Two-Step Method is likely to be the most cost-effective and environmentally sound approach to treating medium to large landscape areas. The bait you apply determines how quickly ants will be controlled and how long the effect will last. Faster acting bait products will work in three to seven days. Slower acting baits can take up to three weeks. There are some products that combine both the fast- and slow-acting ingredients (Amdro Yard Treatment or Extinguish Plus), and they control ants better because they act quickly and last longer. For livestock pastures and hay fields, use Amdro Pro, Esteem, Extinguish or Extinguish Plus.

Always read and follow the application instructions on the label of the product you are using. Determine the size of your property that is infested with the fire ants. Calculate the amount of bait that will be needed. If a small amount of bait is needed, a hand spreader works very well. If a larger amount is needed, a push spreader would be quicker. Apply the bait in swaths, crisscrossing swaths if needed to be assured the bait cover the area completely.

Treat nuisance mounds and new colonies with a contact insecticide on an individual mound basis. Some mound treatments are available as liquid drenches, dusts or granules that are watered into the mound. Ants are only killed if the insecticide contacts them, so proper application is essential. These treatments are most effective when ants are nesting close to the mound surface (as they do when the temperature is mild). Colonies should not be disturbed during treatment. If you use a watering can to apply insecticide, do not use the can later for other purposes.

The effects of the fire ant bait does not last forever, and eventually new colonies will appear. If you do not treat the area again, you can expect an ant infestation to return to its original level over time. Thus, keeping fire ants in check requires a commitment of time and money. Simply monitor your property on a regular basis. If only a few mounds appear, you may wish to use the individual mound treatment. However, if individual mounds start appearing faster than you can keep up with them, then it might be time to do the Texas Two-Step Method once again.

Are fire ants native to the United States?

Red and black imported fire ants (Solenopsis invicta, and S. richter) are native to South America. They were accidentally introduced into the United States in the 1930s through the port of Mobile, Alabama. They were probably in soil used for ships’ ballasts. In Texas, fire ants have been a problem since the 1950s. They now infest about 2/3 of East Texas and have spread throughout the rest of the state. They have spread into New Mexico on a limited basis, and they also have appeared in northern Mexico. Their northward spread has gone as far as Central Oklahoma where their survival depends on freezing soil and temperature conditions. Severe winters tend to push them back.

Will fire ants kill trees?

It is common to see their mounds at the base of trees trunks. Texas A&M horticulturists feel this does not cause any damage to well established trees because the ants in the mound could prey on other insects that are feeding on parts of the tree. In Florida, however, the ants have girdled trunks, and killed newly planted citrus trees. In my yard, it doesn’t matter if the tree is new or old, I want the fire ants gone. If the broadcast method hasn’t taken care of them, then each mound is treated individually.

If you have questions about this article or any of the Extension programs, contact the AgriLife Extension Office at (936) 435-2426 or go to Extension programs serve people of all ages regardless of socioeconomic level, race, color, sex or religion, disability or national origin. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas cooperating. A member of Texas A&M University System and its statewide agriculture programs.

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