Fire ants

Red imported fire ants make a lasting impression with the pain they cause.

If you have ever been stung by a red imported fire ant, I doubt that you have forgotten the experience.

The red imported fire ant is not native to Arizona, and, so far, we have kept them out of our state. If you have any experience at all with this invasive pest, I suspect that you will agree with me. We definitely do not want them!

Years ago, I was one of about 30 Extension agents touring farms and ranches in the Southern states. We started in Raleigh, North Carolina, and ended our tour 10 days later in West Palm Beach, Florida. On one of the stops in Georgia, I encountered the red imported fire ant for the first time.

We were warned ahead of time by the local Extension agents to avoid the fire ant mounds at all costs. “Go around them!!” they said. “Don’t step on them!!” Unfortunately, one of our group did indeed step inadvertently on a mound and ended up being stung many times. Our colleague was in pain and feeling pretty miserable for about 24 hours. Just watching it all take place — the ferocity of the ants, their rapid response to a threat and the fiery pain of the stings, made a lasting impression on me. I decided then and there that we absolutely did not want this invasive pest to make its way to Arizona.

The red imported fire ant is native to the tropics of South America, mainly Brazil and Argentina. It arrived in the United States sometime between 1933 and 1945, they are not sure when, but they do know where. The first colonies in our country began in and near Mobile, Alabama. They suspect that the first ants arrived by cargo ship docking in that harbor. From there it has spread to thirteen states currently. The ant is also found in many different countries worldwide. It is the mission of our Arizona Department of Agriculture to keep them out of Arizona. I wholeheartedly agree with that mission.

Years after my first encounter with the red imported fire ant, I was on yet another tour with colleagues, this time accompanied by my family. We were crossing a grassy area at a farm and I spotted several fire ant mounds in the area. Two colleagues, one from a Southern state with experience with the ant, and one from Michigan who had no prior experience, were walking ahead of us in a group.

Knowing how aggressive these ants could be, I was watching the mounds carefully to warn away my family and colleagues from danger. It was interesting to note that the colleague from the South walked around the mound, while the agent from Michigan, not recognizing the danger, stepped right on one. The colleague from the South knew what the mound represented and the one from Michigan did not. Fortunately, the mounds were not active for one reason or another and evasive action was not needed. Sometimes, however, a lack of knowledge can be the difference between a happy day and one that ends up being not so happy.

To allay any fears arising from this discussion, let me say right here and now that the red imported fire ant is not currently found in Arizona. With that said, there have been colonies found in some places within the state, notably Yuma, but they have, to the best of anyone’s knowledge, been eradicated. Again, that is one of the jobs of the Arizona Department of Agriculture and they are quite diligent and aggressive in dealing with the threats of the pest. Nevertheless, it never hurts to have extra sets of eyes on the ground literally to catch these critters before they become established. For this reason, all residents of Pinal County should become familiar with the insect, learn how to recognize their invasive colonies, and be prepared to report it to proper authorities.

The red imported fire ant is a small ant, They range in size from less than a tenth of an inch to about two tenths. They are quite small but, they also come in different sizes in the same colony, which can be confusing. The head and midsection of the ant are often colored red, from which their name comes, but their third, or last section, is usually colored black.

Now before you go all weird on me and say that you have seen these frequently in the desert, let me pause here for a moment. Yes, there are fire ants that fit the above description native to the desert. However, they are not the red imported fire ant.

In the Arizona desert, there are three species closely related to the red imported fire ant. They have been here close to forever and are native to our area. While their sting can be painful, and they carry the fire ant name, they are not anywhere near as vicious as their South American cousins. Don’t freak out if you think you might have fire ants. You might just have one of the native species in your yard, and that is nothing out of the ordinary.

A critical characteristic makes identification easier. While the native species may have hundreds of individuals living in a den, the red imported fire ant will have many more, in the thousands perhaps. With their superior numbers and their quick response to investigate threats to their dens, it is easy to tell the red imported from the different native species. When the Department of Agriculture people check for fire ants in a container plant shipment from the Southern states, they often take a baseball bat and pound the containers. If ants come boiling out of the containers in large numbers, they know they are probably dealing with a red imported fire ant situation. If you see a mound of loose soil around an entry hole in the ground, just tap the mound with a stick or a garden implement and watch to see if ants in large numbers come boiling out to see what is going on. Again, the number emerging may approximate a thousand, not a hundred individuals.

If you think you have a fire ant invasion, and there is a history that would connect your yard with the Southern states, such as a newly planted tree grown in a nursery there, or plant material has been brought in from one of those states that could have possibly been infested, then it is appropriate to contact a specialist to help identify it. I would recommend that you call the regional office of the Arizona Department of Agriculture. These insects are so small that some of the ways of telling them apart require a microscope to make the distinction.

The bottom line of this discussion is to not get all worried. Right now there are no known colonies of this invasive ant anywhere in Arizona. On the other hand, it is always a good idea to know about unwanted pests and to learn how to be on the lookout for them in case they do appear.

The imported red fire ant is an unfriendly invader in places where it can survive and constant vigilance and prevention are needed to keep it out of Arizona.

If you have questions, you can reach one of our Master Gardener volunteers every week day except Saturday and Sunday between 9 am and 12 pm by calling the Master Gardener hotline at (520) 374-6263. You can also call the Cooperative Extension office, 820 E. Cottonwood Lane, Building C, in Casa Grande at (520) 836-5221, extension 204 and leave a message.


Rick Gibson is a horticulture agent with the Cooperative Extension in Pinal County.