San Antonio Express News
Gardening, Etc
Sunday, March 16, 2003
by Nathan Riggs, Extension Agent-IPM
Texas Cooperative Extension – Bexar County
Last week’s article from the Bexar County Extension office talked of wacky weather and grasshoppers, but also promised more information on fire ants. You want it? You got it!
The title of this week’s article holds more truth than one might think. Springtime means that fire ant mounds across South Texas are brimming with thousands of winged male and female ants just waiting for the right cues to fly out of their home nests, mate with ants from other colonies, and return to the ground to begin colonies of their own. Time for male fire ants, however, is short-lived in spring because they die soon after mating.
Mounds from these early spring mating flights should begin appearing toward the end of summer and mix in with the probable thousands that will already be in place. Yes, you read correctly–thousands!
Fire ant populations were not damaged in the winter of 2002-03 and should be in good shape for 2003. Of course, this begs the question, “What in the heck am I supposed to do to kill all of these darn fire ants?”
Well, killing fire ants is easy. It’s deciding how to kill them or what to kill them with that can be the hard part. Fire ants are very susceptible to insecticides, and there have been no indications that they will become resistant to any insecticides. Having said this, the behavior of a fire ant colony after it has been treated with a dust, liquid, or granular insecticide leads one to believe that they are immune to the treatment. Today’s fire ant colony in Texas usually contains multiple queens that can continue the colony if not killed by a treatment. In fact, this usually does occur in most cases. To effectively kill a fire ant mound, the treatment must be applied and used correctly.
Freshly-built fire ant mounds are extremely vulnerable to a treatment. Ants in a fresh mound are at or near the top and are ripe for killing. A liquid insecticide solution, whether it is orange oil, pyrethrins, boiling water or an insecticide concentrate will do a very nice job in this situation. Dusts and granules are effective too; just be sure to follow the granules with one gallon of water. If you are a person who prefers the low toxicity of fire ant baits, be sure that conditions are dry (not lately in San Antonio!) and that the temperature outdoors is at least 70 degrees F.
Fire ant baits, generally speaking, can be very deadly to fire ants because the bait is collected as food. The amount of actual poison in fire ant baits is extremely small and poses very little threat to birds, humans, pets and even other insects if applied as per label directions. Fire ant baits are formulated on de-fatted corn grits soaked in soybean oil. The oil contains the poison. Since fire ants cannot swallow solid food, they collect the bait pieces and suck the oil off of them. The oil is then spread systematically ant-to-ant through the colony and to the queen and offspring.
Since we are discussing baits, let’s touch on the issue of grits to kill fire ants. As the story goes, ants eat the grits and then their stomachs explode when they drink water. The truth: as is outlined above, fire ants cannot swallow anything solid. Therefore the grits could not possibly kill them as purported. Fire ant colonies that disappear after the application of grits are moving due to the disturbance and not because of death.
Now that we’ve gotten this grits issue behind us, let’s touch briefly on natural, living controls for fire ants. Fire ants have very few natural enemies in the United States. In their native home of Brazil and parts of Argentina, fire ant populations are 80% less than they are in Texas. This is due to other ants, diseases, beetles and phorid fly parasites. In Texas, fire ants’ natural enemies are native ants and the weather. As far as science can tell, sugar ants, carpenter ants, harvester ants, and leaf cutter ants pose no threat to a fire ant colony. However, most of the other 46 or so ant species in Bexar County can and do have a negative impact on fire ants if given the chance. The chance native ants need occurs when fire ant treatments are applied only to mounds when fire ant numbers are low. In dense fire ant populations, there usually aren’t any native ants (or at least very few) to worry about, and a broadcast bait application of 1 lb/acre will do very well.
Fire ants will never be eradicated from Texas. Eventually their populations will stabilize at some level due to a combination of natural enemies, climatic factors and treatment applications. The most important thing to remember about dealing with fire ants is not to quit treating when you’ve knocked their numbers down. Good luck in 2003!
