How not to kill fire ants

10 May
A colony of fire ants (Solenopsis invicta) swarms in response to a disturbance to the mound.

Never attempt to drink fire ants.

Fire ants are the little devils that we here in the south love to hate. As such, there’s a sort of popular mythology that has risen up around them and the methods for getting them to go away.  Browsing forums around the net you can collect these bits of entomological folklore by the dozens.  Some of them are useful and some… not so much.

Blow ‘em up

For example, there’s the ever-popular “grits will make things explode” theory as applied to ants:

“i heard that corn meal (ya know the stuff you can use to make corn bread) is something i heard kills them, they bring it to their nest … and they eat it, but they cant digest it so they explode (not literally, i wish they did though) so they just bloat till they die.”

Leaving aside the likelihood of grits causing anyone to explode there is one gaping flaw to this “common sense” theory.  While corn grit is used as a foundation for several commercial baits (such as Amdro), the key ingredient is the poison-laced oil the ants lick from the surface of the grits.  In fact, due to a sieve plate in their mouths and a constriction in their gut, most adult ants cannot chew or swallow solid food.  Instead, this job falls to the older larvae, who chew and partially digest solid food brought to them by the workers before sharing it via regurgitation.

Ants feed the colony and the queen dies - inaccurate fire ant art

Sorry, Amdro artist, that’s not quite how it works.

Before the evolution of trophallaxis (food sharing by regurgitation) the worker ants apparently acquired their nutrition from the larvae more directly. For example, dracula ants chew through the skin of their young and drink their “blood.”

Let them eat nutrasweet

Death by explosion seems to be a popular predicted outcome of various home remedies… possibly a case of vengeful sadism in response to one too many painful bites.  Still, artificial sweetener?

“The local news put a story about using Equal sugar substitute (I think it is in the blue packages?) on ants – it makes some ants explode. So, it’s bad for people and for ants.. go figure!”

I, personally, have never managed to make ants explode (and believe me, I’ve tried*).  According to Snopes this misconception arose around the same time as a satirical article which claimed that aspartame was first developed as a pesticide before companies “realized they could make a lot more money on it as a sweetener.”  That is to say, it’s a hilarious suggestion, but not true.

Doesn’t mean there aren’t videos about it, though.

…a few explosions would improve this immensely.

Spice things up

“When I lived in Florida, I used powdered cinnamon on the the mounds that were near plants I wanted to work with. This would keep them from crawling out of that mound until a good rain washed it away, then they would come out of there again.”

I can’t speak from any personal experience of fire ants interacting with cinnamon (although one researcher found the cinnamon treatment actually increased ant activity compared to untreated colonies).  There’s another flaw in this methodology, however.

If you watch a fire ant mound you will observe very little activity of ants coming and going from the body of the mound.  In fact, few people realize that fire ants use complex networks of underground tunnels for much of their foraging activity.  A single large colony may have more than a hundred meters of underground tunnels criss-crossing its territory like a subterranean highway system, the entirety of which it can construct (or reconstruct) in under two days (See Tschinkel’s The Fire Ants).  You may have noticed lines of excavated dirt from these tunnels running along the ground after a rain.  Such tunnels allow the workers to shelter from enemies and the heat of the day as they fan out in search of food.  Workers will even sometimes partially bury or cover over food resources they find.  (This is inconvenient for the researcher attempting to count foragers visiting sugar vials in the field.)

Kill them with kindness

Speaking of sugar vials.

“Fire ants hate sugar. If you have ever tried putting out a sugar bait for fire ants, you know what I mean. They will walk a mile to avoid some sugar.”

This is my personal favorite because it is pretty much the complete opposite of true.  Fire ants LOVE sugar.  Yes, they are opportunistic omnivores, and yes, they will scavenge on almost anything made available to them, and yes, proteins and lipids are pretty essential to the development of their young, but simple sugars are tops in terms of maintaining an energetic, active workforce which promotes colony growth.  (Also applies to humans.)

“Your fire ants are different from ours. Ours will absolutely NOT go anywhere near anything sweet. They only eat protein here.” (San Antonio)

Unless your type of fire ant is, say, a completely different species of ant, it’s unlikely the underlying biology and metabolism could accommodate such a radical shift in dietary preferences.  I’ve personally sampled fire ants across Texas, Mississippi, and even Argentina with both sugar and cricket baits, and let me tell you the sugar baits are hella popular.

Fire ants even seek out natural sugar resources, such as visiting extra-floral nectaries on plants (essentially sugar glands) or milking honeydew from aphids and other hemipterans.

Fire ant on cotton leaf drinking at extrafloral nectary.

Fire ant drinking at cotton extrafloral nectary.

Poison their fields and sabotage their supplies

A few of these sugar-based fire ant prevention tips recommend spraying sugar water, or watered-down molasses across your entire property, positing that this will promote microbial growth in the soil and drive off fire ants.

“The use of molasses actually stimulates the micro organisms in the soil, and this activity will drive away fire ants, actually, any type of ant.”

“If you spray or soak their mounds with anything sugary, the decomposition process speeds up on their food supply. The fire ants know this and will abandon a mound contaminated with sugar.”

I honestly can’t answer if there might be some kind of multi-tier effect whereby increased microbes or mold could in some way affect fire ant populations.  I dug through the literature but couldn’t find any study supporting this at all.  Color me skeptical.  If you’d like to draw your own conclusions, here are the few factoids I did dig up:

  • Activity for ant mounds treated with molasses was not significantly different than control mounds at any time (Vogt et al 2002).
  • Sinzogan et al recommends spraying mixes of water and sugar or molasses over fields to attract ants and enhance their foraging activity (2006).
  • Molasses has been used to control soil nematodes (Schenck 2001).
  • Molasses treatments may be good for your plant roots (Welbaum et al 2010).

I’d say that sounds like molasses treatments are a win for everybody!  Except maybe soil nematodes and the person trying to get rid of fire ants.

Wrath of the gods

But what about more direct (and dramatic) concoctions?  Vinegar and baking soda, that old paper-maché volcano stand-by is popular as a nest drench, apparently going for the “ant Pompeii” effect:

[whoops, the previous video got taken down.  here's a different one:]

Meanwhile, a slightly less bubbly version employs club soda:

“I read where a liter of club soda will kill three mounds of Ants pour directly on ant (fire ants) and the Co2 will displace the oxeygen and sufficate them.”

Do these fizzy products actually work?  Elizabeth “Wizzie” Brown at Texas A&M has actually studied the effectiveness of this suggested fire ant cure, along with many other home remedies.  Unfortunately, things that sound too good to be true generally are.  Of the club soda remedy Brown says, “It also claimed that the club soda would leave no toxic residue, would not contaminate ground water and would not indiscriminately kill other insects or harm pets.  Pretty much all that part was true, but what wasn’t true was that it would be effective in killing fire ants, unless of course you happen to drown a few in the process.”

Set them on fire

Some people use a gasoline drench, with or without a match.  I’m not even going to link or quote any examples because this is really, really ILLEGAL.  And it’s hella bad for the ground water, which is even more vital of a natural resource then, say, fossil fuel.  Seriously, shame on you.

Other people employ less toxic things like fire crackers and while it’s probably not a very effective tactic, it’s certainly dramatic.

This is a fire fire ant.

Unfortunately, fizzy, flaming, or not, just dousing the mound probably isn’t going to succeed in drowning, suffocating, or exploding the colony.  Fire ants are well adapted to flood conditions.  Meanwhile, the mounds themselves are only a small part of a much bigger picture.  Fire ants use their mounds seasonally to moderate the temperature of the brood and adult ants.  It’s a great way to warm up after a long chilly night.  Beneath the nest, fire ants dig long, vertical tunnels with occasional flat, round chambers for living quarters.  (Dr. Walter Tschinkel compares them to “shish kebabs on a stick.”)

Seriously, though

“I have been fighting them for 20 years now. Spent tons of money and tricks that did not work. My father even tried to Pee on them. Nothing works.”

What does work?  Commercial baits and toxic drenches can poison the ants, while applications of boiling water provide a non-toxic alternative.  Less fatal drenches may still have some effect.  (For example, orange oil was found to reduce ant activity in one of the papers above.)  Fire ants move around naturally in response to environmental pressures, so sufficient disturbance may induce fire ant colonies to put up a satellite nest or relocate, hopefully to your neighbor’s yard.

Don’t feel too bad.  They’ll be back.

*My mom has a particular anecdote on this topic she loves to tell.  While she was at the door talking to a neighbor, 8-year-old me wandered up and asked “What do we have in this house that can make an explosion?”  I then wandered back into the house.  My mother decided to cut her conversation short.  Early adventures in SCIENCE.

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2 Responses to “How not to kill fire ants”

  1. M. Brummermann May 14, 2013 at 9:46 pm #

    I watched them survive the flooding of Paines Prairie Florida: they formed floating balls of ants (whole colonies I assume) Maybe the outer ones drowned, maybe they switched positions before that could happen. But the majority lived! A raging fire in another part of the preserve killed turtles, drove out snakes (we were there to collect the fleeing ones for studies) and I think the colonies in that area were killed. But who knows?
    I was just confronted with the cornmeal story by a lady from Kentucky. I thought she’d mixed up ants and horses (they DO get colicky in the described way)

    • 6legs2many May 20, 2013 at 1:26 pm #

      Their raft behavior is pretty impressive to see!
      Yeah, I was really surprised the first time someone suggested I pour grits on a mound.

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