By: Jasna Aleksandrova
Red Imported Fire Ants (RIFA) are famous for their aggressive behavior and painful stings. Fire ants were accidentally brought to the United States in the late 1930’s through a port in Mobile, Alabama. It is assumed that they were inside soil that was used as ballast in cargo ships coming to the US from South America. Since ants don’t naturally migrate quickly, they only migrated out of Mobile at the rate of 5 miles per year during the 1930s and 1940s. By 1949 fire ants only populated a 50 mile radius around Mobile and a few additional spots in central Alabama and Mississippi. However, during the 1950s, they spread more rapidly through Arkansas, California, Florida, Georgia, Louisiana, New Mexico, North Carolina, Oklahoma, Puerto Rico, South Carolina, Tennessee, Texas, and Virginia.
Fire ants are very aggressive but are hard to identify because they look a lot like ordinary ants. An identifying characteristic of a fire ant colony is their mound-shaped nest, which differ to some extent based on soil type. If someone disturbs their nests or a food source that they are surrounding, the colony will respond by attacking and stinging the intruder. The first fire ant attacks and releases pheromones which signals the other ants to swarm up the intruder’s legs in a massive attack with repeated stings. Their venom causes pain and the formation of white pustules. Besides the physical pain that they inflict on humans and animals, their mound-building activities lead to crop losses because they feed on the seeds, fruit, leaves, and roots of plants. The ants become more active when temperatures are between 65 and 95 degrees. Their colonies consist of eggs, brood, polymorphic workers, winged males, winged females and one or more reproductive queens, and labor is divided accordingly.
The FDA estimates more than $5 billion is spent annually on medical treatments for fire ant bites. In addition, they cause about $750 million in damage to agricultural assets including veterinary bills, livestock losses and crop losses in infested areas. The U.S. Department of Agriculture (USDA), during an 20-year campaign that they started in 1965, dropped more than 143 million pounds of Mirex across a 77,220 square mile area of land between Texas and Florida, costing close to $200 million. However, every time they did this, they learned that the fire ant population spread farther and faster, they went from having one queen per colony to multiple queens per colony, and therefore they reproduced faster. Not to mention the 20 years of environmental contamination that occurred during that time.
Since 1989, OPIS (The Office of Plant Industry Services) of the Virginia Department of Agriculture and Consumer Services has tried to eradicate RIFA colonies. Between 1989 and 2007 The OPIS treated an average of 33 ant colony sites per year. In 2008, 642 sites were treated in the Tidewater area alone. Since 2009, there have been several areas in Tidewater, like Virginia Beach, Chesapeake and Norfolk, that have been on a federal quarantine list for Red Imported Fire Ants. The quarantine is necessary to keep the fire ants from spreading to the areas of Virginia that are not currently infested.
If you have to deal with one or more RIFA colonies, you can flood the mound(s) with a large volume of liquid containing a contact insecticide, without disturbing the mound prior to application. If you disturb the mound before flooding it then the colony will attack and the queen may be taken deeper into the mound.