If you live in an area where red imported fire ants (RIFA) are a problem, you may already have first hand experience with them. Growing up in south Louisiana, I was very aware of fire ants and of anything that resembled a fire ant nest. Having been stung many times in my life, their aggressive nature made their presence difficult to ignore.
I can’t tell you how many times through the years that I have heard a child crying and seeing the parent frantically brushing off the child’s legs. No one had to ask what had just happened. We all knew the child had probably stepped on a fire ant nest.
Red Imported fire ants have a well deserved reputation. Most problems arise when their nests are disturbed. The ants will fiercely defend their nest from anything that damages it. (Photo courtesy of photographer Scott Bauer, USDA Agricultural Research Center www.forestryimages.org)
Common Victims of Red Imported Fire Ants
Within a second of stepping on a nest, the ants begin to swarm. They aggressively attack anything that remains on or within inches of the disturbed nests. The most commonly stung are children, pets, and farm animals that accidentally disturb them. The sting feels like a burn, which is referenced by the name fire ants. After gripping onto you, they actually inject a venom. Older adults and those who are less mobile need to be especially careful. It is important that adults know what the ant beds look like and make an effort not to disturb them.
Newly born farm animals, such as calves, goats, etc, that are still too young to move quickly have been killed by stumbling or falling into large nests. A defense mechanism in young calves, for example, is to remain still when threatened. This is the worse thing they can do. Horned toads, turtles, lizards, quail and other birds and animals are also killed by fire ants.
Red Imported fire ants are native to South America. DNA of the red imported fire ants in the U.S. have determined the original ants arrived from Argentina on ships via the gulf port at Mobile, Alabama.
There are currently about six species of fire ants in the U.S., but two primary species: By far, the major species is the red imported fire ant. The second is probably the black imported fire ant.
The red imported fire ant, often referred as RIFA, have spread throughout the southern U.S. are now found in the following states, beginning from the Southeast: Florida, Georgia, South Carolina, North Carolina, Virginia, Maryland, Alabama, Mississippi, Tennessee, Arkansas, Louisiana, Texas, Oklahoma and also throughout Puerto Rico. They have also been reported in New Mexico, Arizona, and California, but their presence is very limited in comparison.
Bermuda Hay From Texas and Fire Ants
During a drought in Missouri, local farmers were going to Texas for hay. We were warned about the possibility of fire ants coming into the state inside the haybales. If it happened I haven't seen any evidence of them making nests here.
Outside the U.S., they are found in Australia, Taiwan, the Philippines, and in parts of China. Their arrival to those countries was probably by ship, as well, hidden away in contaminated soil. DNA of the fire ants show red imported fire ants outside of U.S. (excluding South America) actually came the United States. They are expected to move south into Mexico into areas where conditions favor them.
The second type is the black imported fire ant. The black imported fire ant is currently only found in Alabama and in northern Mississippi.
Each colony of red imported fire ants consists of at least one queen, several types of workers, winged males and winged females. The winged females are unmated queens. The queen loses her wings as soon as she locates a suitable place to start a new colony.
One queen can lay as many as 2000 eggs a day. Workers inside the nest will have different jobs ranging from caring for the eggs and feeding the queen to guarding the nest. A typical nest with a single queen can have up to 200.000 workers ants.
Tunnels can extend to six feet underground. During hot, dry weather or when the queen is in danger, worker ants will transport the queen to the lower levels.
The primary food source of Red imported fire ants varies. It includes plant sugars from vegetation and fruits, insect secretions such as honeydew, seeds, and nuts. They will also consume insects, small rodents, birds and reptiles.
There are single queen colonies and multiple queen colonies. Each type of colony behaves differently as described below.
Single Queen Colonies
In locations where each mound has a single queen, different fire ant colonies will fight with each other. The result is that there will be less mounds per acre, averaging between 75 to 100. Winged queens that leave the colony flying up to 1 mile to locate a suitable site for a new colony.
Multiple Queen Colonies
However, a fairly new phenomenon has been observed in some states. Since the 1970’s researchers have noticed colonies with several queens per nest. These colonies don’t generally fight with neighboring nests, which results in more nests per acre.
Nests in these situations can average 500 colonies per acre with each colony numbering as many as 500,000 workers. Frequently, queens will not fly away to start a new colony, but will simply split off from a nest and start a new colony a short distance away.
Fortunately, RIFA don’t attack in nunbers indiscriminately, but will only attack to defend their nests. Individuals may sting if they get on you while working in the garden, lawn or with trees that contain ants.
However, most individual stings are on the same frequency as other ants. Most attacks occur when a nest is disturbed, usually from being stepped on.
In a common scenario, the nest is disturbed and the ants swarm up the leg inflicting numerous painful stings. They will swarm over any part of the body or instrument used to damage the nest.
I remember as a child being attacked by poking the nests with a stick and not realizing how quickly the ants were crawling up the stick. This was a common practice among children, but should be severely discouraged. The picture may be hard to look at, but shows what can happen in just a few seconds.
When a fire ant stings, it injects a potent venom into the skin containing a narcotizing alkaloid. This venom destroys the skin cells at the sting site resulting is a swollen, white pustule that forms within 24 to 72 hours.
In addition, the site will usually result in intense itching that can last for days or weeks. If the skin over the site is scratched off, care should be taken to keep them from becoming infected. (Photo courtesy of photographer Murry S. Blum, University of Georgia, www.invasive.org)
The sting of a red imported fire ant is usually only serious if the person stung has an allergic reaction. A normal reaction will be as described above. Allergic reactions to red imported fire ants will be similar to other insect bites or stings.
If you are allergic, minor reactions may range from redness, rashes and swelling extending beyond the sting site. More severe reactions may include sweating, fever, labored breathing, restlessness or anxiety, rapid pulse, dizziness, blood pressure change or passing out.
Rare, but extreme cases could involve anaphylactic shock or death. Immediate medical treatment may be necessary for reactions beyond the normal and most definitely for severe reactions. Fortunately, for most people, even those having several stings will not require any medical treatment.
Tip When Working Around Fire Ants
If you are doing yard work in areas where fire ants live, coat your hands with talcum powder. The powder clogs the ant's pores and coats the feelers, so it is thrown into total confusion.
Red imported fire ants are a quarantine insect in the areas it is found. It is currently impossible to completely eradicate these fire ants. Reducing their numbers and controlling their spread is the only option. The current red imported fire ant controls can greatly reduce fire ant numbers, but they may not prevent re-infestation.
How to Kill Fire Ants
The most often asked question is how to kill fire ants. Modern methods are much better than previous one. Previous attempts at killing fire ants may have actually worsened the problem rather than helping.
By broadcasting insecticides over broad areas, other insects and ants that were hostile to fire ants were also controlled. When fire ants later spread into those areas, they found little resistance. Poor control methods that result in killing fire ants without destroying the queen will temporarily reduce numbers, but not completely control the nest.
Home Remedy for Fire Ants
Many home remedies for red imported fire ants have been used over the years. Some work better than others, but most have an element of danger involved that could result in injury. Extreme care should be used no matter what method is used. Some home remedies for killing fire ants include:
Boiling water slowly and carefully poured over the nest is effective in killing the majority of ants and collapsing the nest. Depending on the size of the nest, it may take 3 or more gallons. The best time to pour the water is during cool summer mornings.
At this time of day the ants will be nearest to the surface. As the ground heats up at mid day, the ants will move deeper into the nest where soils are cooler. Be careful not to splash the water, but pour it gently. Splashing water could burn you or splash ants onto you.
If you are using a large pot to boil in, be very careful carrying it out. Use oven mitts to carry the pan out to the mound being careful not to splash any water on you. Make sure there are no children or pets in the area.
Diesel Fuel or Gasoline
This remedy is not recommended, though it is sometimes used. The concept is that the fuel kills on contact and the vapors will move through the nest killing more insects.
If you feel you need to use fuel, then make it diesel fuel. It burns more slowly than gasoline. It is possible that fuels could contaminate soil if you have very sandy soil or could leach into the water supply. Igniting the fuel is very dangerous and performed carefully with water nearby.
Digging out the nest
This is another remedy, but should be used only with caution. The concept is to dig out the nest using a shovel. Before digging, talcum powder is used to coat the handle and bucket.
Talc is supposed to discourage the ants from crawling. Digging should take place on cool morning when the ants are nearest the surface. This method also assumes the ground can be dug up easily with little effort. This works best for smaller nests. Pouring boiling water over the nest will kill the ants. Diesel fuel will work as well.
There are many different products labeled for red imported fire ants. With these products, total elimination of fire ants should not be expected.
A decline in as much as 90% or more of red imported fire ants can be expected with some products. Be aware that reinfestation is possible. These products include:
Poison baits mixed with edible liquids, such as soybean oil, that the ants could then carry back to the nest. Once inside the nest, the ants regurgitate the liquids to be consumed by other ants. The baits should be placed near the nest so it is easily found. Once the queen consumes the bait, she will die soon.
Broadcast insecticides are spread over the entire lawn. Foraging ants will find the bait and carry it back to the nest. The benefit of broadcast insecticides is that you don’t need to treat any individual nest. Hidden nests can still be controlled. Hydramethylnon is an ingredient labeled for control of fire ants.
Ant Growth Regulators
These are ingredients that prevent the queen from laying eggs. When the queen is not laying eggs, the workers will not care for her and she will die. The remaining ants will quickly decline as well. These regulators are often combined with other insecticides. Products like Ascend, Logic and Award contain growth regulators.
Fire ant insecticide drenches are products designed to be mixed with several gallons of water and poured directly on the nest. The liquid is poured around the base of the nest and also over the top. Gravity carries the insecticide down through the vertical and horizontal tunnels killing on contact. The colony can be controlled in as little as an hour from the time the drench was applied. Some work more slowly, so read the label carefully.
There are also aerosol products labeled for use on RIFA colonies. Cans come with a long tube that attaches to the nozzle of the can. The tube penetrates the nest at the same time the trigger is depressed. The chemical and vapor spread quickly through the nest.
Quick list of Red Imported Fire Ant Products
Quick list of fire ant baits and insecticide product trade names: Amdro, Award or Logic, Ascend, Extinguish or Justice, Spectracide Fire Ant Bait, Eliminator Fire Ant Bait, Orthene, Talstar, Rapid Kill, Citrex Fire Ant Killer, and others. Always follow label directions. Read the label completely before opening or using the product.
There are a number of diseases that have been observed in ant populations. Work is being done to see how these diseases may be used to control ant populations.
Phorid flies are tiny parasitic flies that oviposit on fire ants found outside the nest. These flies are common in South America and is said to be responsible for keeping fire ants under control.
Some fly species are believed to be host specific to red imported fire ants. When the flies are active around the nest ants go into defense mode. They stop foraging and retreat to the safety of the nest.
The fly's single mission in life is to oviposit an egg onto the fire ant just behind the head. The maggot enters the ant's head cavity to feed and eventually decapitating the ant. The maggot then uses the body cavity to pupate.
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