by Susan Whitacre, Fort Bend Associate Master Gardener
That could be a newspaper headline, and I have the scarred ankles to prove it! If you tend your home garden, hike through open fields, picnic in a park or mow your lawn, you have almost certainly experienced an attack of these ravenous aggressors. What are these invaders that can disrupt local ecology, impact local economies and, on rare occasions, take the life of vulnerable humans and wildlife?
The U.S. saga of these silent invaders began over 100 years ago when the solenopsis richteri forei (
black fire ant) first arrived at the port of Mobile, Alabama, in cargo ships from South America. Around 1930 the more aggressive red imported fire ant (RIFA) solenopsis invicta Buren followed, arriving at the port in the ballast of cargo ships from the Paraguay River Floodplains. By the 1950’s the red fire ant had become an unwelcome and widespread presence in Texas and now infests over two-thirds of eastern Texas, including a local stronghold in
Fort Bend County.
RIFAs’ wanderlust, its ability to reproduce quickly, its aggressive nature and the absence of natural predators weren’t the only factors contributing to its rapid spread and invasive foothold in Texas. Truckers, ranchers, travelers, outdoor enthusiasts, and gardeners like ourselves, have all played a part by unknowingly transporting these hitchhikers in baled hay, nursery stock, sod, soil, firewood, and heavy equipment.
Nature’s Way – The Horrid Phorid Cycle
In an effort to naturally control the RIFA population and its invasive spread, scientists at the Brackenridge Field Laboratory successfully identified a predator; the phorid fly Pseudacteon in its native habitat in South America, and introduced it to Texas in 1999.
Now a silent but deadly scenario plays out like a Hollywood horror flick in our own backyards. The female phorid fly is irresistibly drawn to swarming mounds in its search for a host in which to deposit its eggs. As it circles the swarming mound for its prey, the frenzied fire ant colony wreaks havoc upon itself, stampeding each other and disturbing the nest in its attempt to retreat. Opportunistic native ants attack, taking advantage of the mayhem and move in to reclaim lost territory.
Once the phorid fly identifies a host RIFA, it swoops down and injects its egg into the thorax of the unfortunate ant. When the larval maggot hatches, it migrates to the head and devours the ant’s brain and surrounding tissue, eventually causing the RIFA’s head to pop off. The larva develops to maturity in the skull and when the adult phorid fly emerges, it begins the horrid phorid cycle once again!
In addition to The Imported Fire Ant Phorid Fly Rearing and Release Program, The Animal Plant Health Inspection Service (APHIS at aphis.usda.gov), a division of the USDA, began instituting programs in 2002 in cooperation with states, universities, and the Agricultural Research Service to introduce biological control agents. These programs include quarantining nursery plants, hay and some farm equipment.
Although Agricultural Inspectors follow tight protocols to regulate and monitor the movement of certain products from quarantined areas by inspecting trucks, collecting samples, treating and disposing of infected shipments and issuing permits certifying loads are fire ant free, the hitchhiking RIFA have still migrated as far west as California, as far north as Virginia and as far south as Florida, Texas and Puerto Rico.
The Painful Reality of RIFA
From personal experience as a home gardener, the most efficient way to identify these pests, is stepping barefoot into a fire ant mound. It’s not something I would recommend but it is effective! Within seconds you will witness the aggressive nature of these ants as they swarm from the mound, travel onto your feet and up your legs … while ravenously biting with their mandibles and repeatedly injecting you with venom from their stingers, setting your legs on fire with pain. Red welts surface immediately and over a few days, they develop an unsightly white head.
These nasty bites can leave permanent scars, become infected or even be life-threatening in some vulnerable adults, children and animals. Cold compresses and pain-killing sprays can ease the burning, however if the reactions are severe, it is important to get to a medical emergency room immediately.
There is a less painful approach! After a heavy rain, you might notice mounds of loose excavated soil in the open, sunny areas of your yard, along sidewalks, beside air conditioners or in fields. RIFA mounds are distinct in that they have no visible entrance hole, and vibrations (i.e. stomping your foot, mowing a lawn) will cause them to swarm. Wearing gloves and boots in the garden especially after a heavy rain is advisable because you may find that RIFAs have migrated to your potted plants, compost piles, flower beds and mulched areas.
The More You Know These Ants, The More You Admire Them!
RIFA aren’t all bad. They prey on garden pests like cinch bugs, flea larvae, cockroach eggs and ticks, and help to reduce compacted soil by moving and fluffing the earth as they build their mounds.
You have to admire RIFA for their ability to organize in a split second when threatened and marvel at how these social, minuscule ants, gather in massive underground colonies and build impressive mounds to protect their progeny.
The life cycle begins within 28 hours of mating, when the newly fertilized queen identifies a nesting area, sheds her wings, excavates a simple chamber, seals herself in and produces her first hatch of 10-25 eggs. In about 10 days, the larvae will hatch. The Queen feeds her firstborn with regurgitated liquids. They will develop into the sterile wingless workers at the bottom of the totem pole of RIFA hierarchy.
Their established hierarchy is quite impressive, too. The worker ants act as highly-trained bouncers, standing guard over the nest, protecting it from intruders, caring for the larvae and building additional chambers for the growing colony. These workers also forage for food to mouth-feed the Queen with regurgitated liquids and move the Queen to safety if threatened. Remarkably, a mature queen fed by her workers can lay up to 200 eggs a DAY! The mature colony can be 24 inches high, house a half-a-million workers, hundreds of winged reproductives and multiple queens, within just three years.
The reproductives are winged ants which live in the mound until the irresistible call-of-the-wild entices them to take flight. Their mission is to reproduce and once mating is accomplished, the male will soon die. The workers live just five weeks, but the queen can live up to seven years.
Fort Bend County Gains Surprising New Respect for RIFA
Hurricane Harvey brought many Houstonians a new respect and admiration for the resilience of RIFA. We can all remember seeing foreboding colonies of RIFA, held together by interlocking legs, floating along in the Bayous, and through the flood waters. Although their colonies were flooded under feet of rain and run-off water, RIFA employed a remarkable survival strategy, creating what appeared to be flotillas of small islands floating the waterways in a cooperative migration to higher dry ground.
What You Can Do
Home gardeners, you can make a real impact on the spread and growth of the RIFA in Fort Bend County. Learn about various control methods and do your part to prevent their transportation and spread into new areas.
- Take advantage of the invaluable resources of Texas A&M AgriLife Extension by visiting tamu.edu to learn the application and safety guidelines for chemical, organic and natural methods to control RIFA populations in Fort Bend County and the pros and cons of corn-based granules, and organic options including botanical insecticides.
- Following local experts like Dr. Paul R Nester, Extension Program Specialist II – Houston Metro Area http://fireant.tamu.edu/controlmethods/index.php).
- Take your Momma’s advice, “Don’t offer hitchhikers a ride!” Clean your camping gear, wipe off your boots, and check firewood before moving it.
- Consider a cooperative treatment effort with your neighbors, similar to the one LSU AgCenter scientists coordinated. They treated 300 acres of contiguous properties in a Baton Rouge subdivision and reduced the RIFA population by 90% in just two years!
Bibliography of Research References
- USDA/APHIS United States Department of Agriculture-Animal and Plant Health Inspection Service, aphis.usda.gov, Jan 2, 2020 Imported Fire Ants, https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/imported-fire-ants/ct_imported_fire_ants
- Imported Fire Ant Program Manual 2/2019 – United States Department of Agriculture, https://www.aphis.usda.gov/import_export/plants/manuals/domestic/downloads/fire_ant.pdf
- Treatment Manual – http://www.aphis.usda.gov/import_export/plants/manuals/ports/downloads/treatment.pdf
- Texas Imported Fire Ant Research and Management Project, http://fireant.tamu.edu/
- Fire Ants, Master Gardener Module ant-pests.extension.org/fire-ants-master-gardener-module/
- Dr. Paul R Nester, Extension Program Specialist II – IPM – Houston Metro Area, ant-pests.extension.org/tag/fire-ant-control-products/
- Medical Problems and Treatment Considerations of the Red Imported Ant, fireant.tamu.edu/files/2014/03/ENTO_005.pdf
- Texas Pest Ant Identification: An Illustrated Key to Common Pest Ants and Fire Ant Species, tamu.edu/files/2014/03/ENTO_001.pdf
- Fire Ant-Attacking Fly spreading rapidly in Texas. 9/2006, news.utexas.edu/2006/09/27/
- The UT at Austin Fire Ant Project – web.biosci.utexas.edu/fireant/
- Natural, Organic and Alternative Methods for Imported Fire Ant Management-Texas A&M AgriLife Extension – agrilifeextension.tamu.edu/library/landscaping/