Tried and true corn method works well in south Texas citrus ALTHOUGH many methods of fire ant control are in the developmental stages, Dr. J. Victor French, entomologist at the Texas A & M Kingsville Citrus Center in Weslaco, says the best method of managing fire ants in citrus today is the tried and true Texas Two-Step.
A formulated bait of corn grits, soybean oil and chemical growth regulator is spread around the mound. The worker ants pick up the bait and take it inside, feeding it to the queen. The compound sterilizes a queen. Seven to 10 days later, the mound is drenched with a fast-acting contact chemical that rapidly kills the worker ants.
Tropical fire ants have long been a problem in south Texas. But in the last four years a different species has been marching, and sometimes hitchhiking, its way into south Texas. The red imported fire ant, it is even more determined than the indigenous fire ant to cause havoc in its new home. It now infests 56 million acres in Texas.
According to French, there is evidence that the tropical and imported ants are cross breeding, possibly producing a hybrid ant that will be even more difficult to manage.
The imported fire ant colony, unlike the tropical ant, often has multiple queens. French describes them as "real egg-laying machines," able to produce up to 1,500 eggs daily. Besides being prolific, imported fire ants are vicious, capable of inflicting hundreds of stings in an instant.
When a mound is disturbed, it appears to be boiling, as thousands of ants quickly exit, ready to defend their queen and attack any intruder.
Unlike the tropical fire ants' mounds of loose soil, the imported fire ants' mounds are domed hills of crusted earth sometimes two to three feet high.
Fire ants feed on seeds, young plants, fruits, and other plant parts of various crops. A recent estimate shows fire ants causing some $300 million in yearly losses in Texas.
Imported fire ants sting calves and other domestic animals, resulting in increased veterinary expenses, decreased animal quality, blindness, or even death. A recent survey found that the beef cattle industry alone suffered losses of around $67 million annually due to ants.
Since fire ants can destroy eggs, they also are threat to the bobwhite quail population.
It is often difficult to get pickers to work in fields and orchards that are infested with fire ants. The tourist industry suffers, too, when visitors who come to fish or hunt are discouraged by the presence of these vicious, stinging insects.
The Texas citrus industry is vulnerable to fire ants. Young trees are wrapped with polyurethane for three or more years to protect them from freezing. The ants burrow underneath the wrap and often establish a colony in the soil at the base of the tree. They eventually girdle the tree, causing the top to die off.
They also open up lesions that allow the footrot fungus to enter, eventually killing a tree. Before the ants are discovered, the damage often has already been done.
Fire ants may damage full-grown trees by driving off beneficial insect predators and parasites of citrus insect pests aphids, mealy-bugs, white flies and soft scales, which then become more prevalent and seriously damage the tree.
French says that before treating ants, researchers want to know the activity in a mound. He often places a small plastic tube holding talcum powder, leaving it in the mound for about a minute and then retrieving it. If it is an active imported fire ant mound, there are often over 1,000 ants captured. He then treats the mound using the Texas Two-Step Method.
A week after the final chemical treatment, he goes through the same tube-placement process and might retrieve 50 or fewer ants in a minute. A month later they are usually all gone.
This chemical method of managing the imported fire ant problem may be replaced in the future by other non-chemical treatments that are now in the experimental stage and include the following:
- In 1999, one species of the Brazilian phorid fly, a natural enemy of the fire ant, was mass produced and experimentally released in 11 locations in Texas. The fly has been recovered from four of these sites in spring 2000, indicating the flies are becoming established. Research is being done at the University of Texas in Austin.
- Scientists at Texas Tech University have completed field studies of a fungus, Beauveria bassiana, that show the fungus to be highly effective in killing imported fire ants. They have genetically marked the fungus so they can track it in ant colonies.
Scientists also have found five different Texas ant species that can successfully eliminate small red imported fire ant colonies.
- A new attractant and repellent is also being tested by the Agricultural Research Service. This compound could be used in combination with water soluble chemical toxicants to create baits that would be attractive to multiple ant species.
Until these new treatments are marketable, French will stick with the good old Texas Two-Step to control the red imported fire ant. "We may never fully eliminate them, but we are finding ways to manage them, at least.