By: Faith Oi
Last weekend, the temperature got up into the 80s in Gainesville, Fla. I could not resist doing a little gardening, because hacking away at dead vegetation is therapeutic for me.
As I walked through some mulch, I kept feeling something “scraping” my ankle. When I looked down, there were fire ants crawling up my leg.
In our sandy soils, fire ant mounds are not always obvious — until you step in them!
Fire ants and their control have seemed to drop in importance to the pest management industry when compared with some of the other invasive ant species like the Rasberry crazy ant in Texas or the Caribbean crazy ant in Florida. That is, unless you have been sued for failing to control these stinging ants. With this in mind, I thought it might be a good idea to review a little bit about the fire ant and general baiting tips.
The Ant. This is how an academic would describe fire ants: All ants fall into the insect family Formicidae. Fire ants belong to the subfamily Myrmicinae, genus Solenopsis. There are several species belonging to the group. The most notorious is the red imported fire ant, Solenopsis invicta. There is also a “native” fire ant, S. geminata.
Both species have a two-segmented waist. These two species are difficult to differentiate in the field. The most reliable character seems to be the presence of “a middle tooth on the anterior clypeal margin” on the invicta species. And their gaster is armed with a stinger. No kidding.
Quite frankly, I was not looking that closely when they were stinging me. And I did not have the presence of mind to put them in a vial of alcohol without crushing them for future identification. I smashed them as I furiously tried to brush them off, triggering an additional attack because of the alarm pheromone that is released, signaling the dying ants’ sisters for help.
How do you know that you are dealing with fire ants in the field? The mound is a dead give-away. It acts not only to house the ants, but as a thermoregulator of sorts.
Why is this important? If you try and treat when it is too cold or too hot, the ants will have taken cover, deep in the soil. Your treatment will not be as effective. Also, when the red imported ant stings, it will leave a welt with a pustule. The native fire ant stings tend not to leave a pustule.
When is it a good time to bait? A good rule of thumb is to bait on a good day to have a picnic — when temperatures are between 70 degrees Fahrenheit and 90 degrees Fahrenheit, and not right before or right after a rain (or irrigation). The time of year is also important. While March 7 may have been a good time to bait, it may not have resulted in an effective treatment because brood production is probably not very high now. In Florida, I will probably have to wait a week or two.
In general, I recommend baiting because it exploits the ant’s foraging behavior and you are more apt to get the small mounds or “flat” mounds that we see in sandy soils.
For additional information on fire ants and their control, I recommend a page on the eXtension Web site. It was developed and is maintained by the fire ant researchers who work with the industry to produce better products and control methods.
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