Ants come in many shapes, colors and sizes. There are over 1,000 species of ant in the United States alone. Ants behaviors are just as diverse as they are. We have many colors of them, some that sting, some that steal, some that impersonate, some that do acrobatics when hurt. But the most notorious ants are the red import fire ants. Their story is the story of how fire ants took over America. In the early 1900’s, two fire ant species were mistakenly imported to the United States through Mobile, Alabama. From there, they have spread across the southern portion of the country from ocean to ocean.
These ants have come to infest many yards, golf courses, fields and so much more. They have pushed out many indigenous species and consumed huge amounts of ornamental and crop plants. Entomologists have worked tirelessly to inhibit their progress and remove them from the United States entirely, but have been unsuccessful. How do they do it?
In 1918, a ship came to port from Brazil with some extra cargo, entering the port of Mobile, Alabama. This cargo was the black imported fire ant. It is believed that it came in the soil used for ships ballast. This ant has spread to parts of Mississippi and Alabama, but hasn’t gotten much farther than that. Sometime in the 1930’s or 40’s, the red imported fire ant made the same trip. It is indigenous to the state of Mato Grosso in Brazil. This is how fire ants took over America.
Today the red imported fire ant has infested more than 260 million acres of land over 13 states. These states include all the states from southern North Carolina and Florida to the western parts of California. This ant has no natural predators, competitors or parasites to keep its numbers down, so it runs rampant.
DAMAGE CAUSED BY FIRE ANTS
Since this ant has come to our shores, it has interfered with the ecosystem of animals and plants. They hurt plants, other beneficial ants, crops, wildlife, even power lines can be damaged. They weren’t named “100 of the World’s Worst” by the Invasive Species Specialist Group for nothing!
As the threat of these ants became apparent, efforts to subdue these invasive species started to grow. Pesticide sprays, granules and baits started appearing on the market. Some of these worked well and others didn’t, but nothing could stop the spread of these pests. These ants even adapted to these attacks by becoming multi queen colonies. Now, if separated, these queens can create a new colony. And if one queen is killed, the colony will continue with the other queens.
WHAT HAVE WE DONE TO STOP THEM?
Besides pesticides, entomologists have tried to introduce predators, pathogens, parasites and viruses to limit the spread of red imported fire ants. The phorid fly is a natural parasite of the fire ant that is found in Brazil, where the red imported fire ant is indigenous. These flies inject their eggs into the ants bodies to hatch and eat the ant. Of the twenty or so species found in Brazil, four have been introduced here in the United States. It has helped little in the control of these ants.
The microsporidian pathogen Kneallhazia solenopsae is a common disease in Brazil that attacks red imported fire ant colonies. Once infected, they shorten the life span of these insects. Also, when a queen is infected, she will lay fewer eggs, and some times no eggs. This results in colony decline.
WHAT ABOUT VIRUSES?
There are four viruses that are showing to be effective at infecting red imported ant colonies. Of these four viruses, only SINV-3 has been field tested in parts of Florida. It has been shown to be a successful way of controlling fire ants. This virus somehow interferes with normal foraging behavior. Workers no longer forage for food, and the colony starts to starve. This virus can be delivered in a bait form, is species specific, and is easily transmitted to the ant colony.