Fire ants in compost bin

Hi, I have a simple compost bin in a storage container/plastic tub with lid and recently fire ants have moved in. We have a lot of fire ants down here in the southeast. I'm not sure what to do about it, I'd rather not use powder to kill them, compost doesn't seems like a good place for that. I've used borax and sugar water mix with no results. Any suggestions? Thank you!

Welcome to Permies!

I have heard good things about orange oil killing fire ants... but I'm not sure the effect it might have on the compost. I imagine it might slow down the process.

If they are moving in and out then spray or pour on the vinegar.  That will end your problem.

If they are not moving then my suggestion would be to go ahead and spray the vinegar and hope that does affect the compost too much.

Thanks for the replies. I also just found them in my large compost lasagna piles as well :/

How is the moisture level in your compost?

I wonder if perhaps that it is more on the dryer side. If you could manage to keep them on the wetter end, you might discourage the fire ants. I'm just spit balling however because I do not have fire ants in my area.

I'm also suggesting making your compost more moist, but have to admit I have no experience with fire ants (that I'm aware of)

My son grows peppers and they love the raised beds of peppers, which comparatively in the veggie world can take pretty dry conditions. He has figured out that a steady tiny small stream set in the middle of the bed/ pot/ etc drives all of the fire ants out. I have adopted it for my compost too because of what you are mentioning. If one night doesn't do it, we increase the flow ever so slightly and do another night. Hoping you have water access that would allow you this experiment! Best of luck. And like many permies say, the problem is often speaking to you. I do find when they arrive it is because my compost is not adequately moist. Also they do a brilliant job of turning clay soil into workable Earth, for what its worth those mean ants do have a place and are communicating to us stewards!

Diatomaceous earth kills anything with an exoskeleton but doesn’t harm worms. I have it in my compost pile with no ill effects. All that stuff is is powdered fossils basically.

Good morning and thank you for the replies. As many of you have suspected, my compost bin and lasagna layers are on the dry side. It's been quite dry here and no reals rains for a while. So that's certainly an area I can improve on.
I like that idea of the little stream, I'll try that soon as well. I do have DE as mentioned, was wondering if I could use that or not, I was worried about hurting the worms, but now I know it won't bother them. Thank you all for your ideas, I'll try some things and see what works!

Hello! I currently live in Texas, (just realized I never updated my profile's location lol) and invasive Fire Ants have been a problem in my yard since I got here. You've got a couple options.

What moves them to another location:
- churning the compost. If you disturb their nest significantly, the queen will move to a nearby location to start a new mound.
- Pouring so much cold water on them that it disturbs their nest significantly. Power sprayer!

What immediately kills the ants:
- Spinosad ant bait. It's a pest killer produced through cultivating a type of naturally occurring soil-borne bacteria called Saccharopolyspora spinosa. The bacteria produces goop that's toxic to many insects (including ants), but entirely harmless to vertebrates. The microbe's metabolism goop is harvested in bulk and used to coat a tasty ant treat, which you'd spread around your compost bin for the ants to bring back into the nest, feed to their queen, and kill her & any in the mound who partake.  
Unfortunately, it does also function on a wide variety of other bugs, but other soil microbes break it down quickly- so once you've applied it and you're certain the fire ant mound is dead, you can go back and repeatedly drench the area you applied with water to work it into the soil layer for microbes to take care of... or note when there's a multi-day rainstorm coming, and apply it in a ring around the compost 2-3 days before the storm.
I know Permies doesn't like poisons of any kind, and I understand if my post gets taken down with that rule in mind.

What MAY be able to kill the mound
- DRENCHING the compost bin with gallons and gallons of BOILING water. If you can boil/steam the queen to death, you kill the mound.
- Opening up the compost bin layers and SCORCHING it, layer by layer with a propane torch. Roast the queen, kill the mound. This also involves deliberately ticking off fire ants AND has a risk of accidentally starting a fire you didn't want, so.... be careful.

Older Fire Ant mounds can be up to 6 feet deep in loose soils, and even in newer ones the queen is usually in the deepest chambers, 1-3 feet underground.  Hopefully yours is shallow, and mostly in the bin itself.

What doesn't work:
- Cold Water drenching the mound. They don't give a sh!t. They evolved to endure yearly tropical floods, and just float up to the top. As soon as the nest isn't fully submerged, they're gucci. Back to business as usual.
- Diatomaceous Earth is moderately effective at killing ants which are out roaming, but the queen never leaves the heart of the colony, so you'll never get her with that.
- Vinegar or Lemon Juice:  The acid may destroy pheromone trails, and the smell may repulse exploring ants, but it won't kill a mound.

If you want to experiment with GALLONS of vinegar to try to pickle the queen, please come back and report your findings on its effectiveness.

Great info, thank you. I forgot about Spinosad. I had used it once before on aphids on my azelia bushes in combination with DE and it worked quite well. Didn't even think about it for ants. I bet you have it much worse in TX than eastern NC. I moved here last year so this fire ant thing is new for me. They're popping up all over the yard so I'm definitely going to try what I've learned here and put it to good use.

Raising the moisture level definitely helped. They moved out of my compost bin. However, they're still in my compost lasagna, since the seasonal rains have been pouring down, I think they like the high ground that the lasagna compost provides, I suppose they can live there for a while until I'm ready to use it 🙂

Sarah Petis wrote:Raising the moisture level definitely helped. They moved out of my compost bin. However, they're still in my compost lasagna, since the seasonal rains have been pouring down, I think they like the high ground that the lasagna compost provides, I suppose they can live there for a while until I'm ready to use it 🙂

I also have lots of fire ants and have decided that if they want to be in the mulch or the compost, they can have it (especially if it means they're not in one of my garden beds). If they're somewhere problematic, I'll protect the plants and dump hot water on the nest holes, but you never know where they'll move next and the next site might be even worse. When it's time to turn the compost or mulch i'll give it one big turn and then go away for 24 hours, give them time to evacuate before coming back for the actual turning, spares me bites.

Okay, I'm going to be the hate magnet in this thread. I LOVE ants in my plants. (Wasps, too, but that's for another discussion.) I actually go around the yard (and the neighbor's yard - and the other neighbors' yards) to find fire ant colonies. I scoop them up with a shovel and bring them home, depositing them all around my garden.

As Suzette noted above, fire ants are great at penetrating hard clay. Besides just loosening the soil (which is reason enough in my book to invite them in), they also provide aeration, fertilizer, and pest protection. I used to be a skeptic, right up to the day I got covered up to the elbow while picking tomatoes, with all bites and privileges thereunto appertaining. I resolved to eliminate them all the very next day - until I noticed the tomato plant that was growing in soil infested with ants was also twice as big, twice as green, and had twice as many tomatoes as its ant-free neighbors. So I decided to encourage them. After three or four weeks they usually move on, leaving behind a mound of fluffy, fertile soil that I didn't have to dig.

I do understand how fire ants can be a real hazard to gardeners, families and livestock in other ecosystems, but for my half acre out on the country edge of Deep South suburbia, they're a real benefit to the garden, and a delight to have around.

We have the big fire ants on our prairie grasslands. They have high mounds, 18" or so and they are in the same place for what seems like decades. I do not disturb as they are a part of the complex prairie ecosystem. I also love the smaller burrowing ants that show up soon after a burn, they leave small mounds and are the first sign of life after the beneficial burning. Modern man has been led astray in the vilification of bugs and weeds, these are mother nature's unpaid workers and should be welcomed for the hard work they do.

I stand corrected on the prairie ants as they are not a fire ant as such, but they do bite.

AI Overview    

Prairie biting ants, often field ants (Formica spp.) or prairie mound ants (Formica montana), are native insects that build large, 1–2 foot high, 3–4 foot wide, or greater, soil mounds in open grasslands and meadows. They are crucial for soil aeration but can inflict painful bites, releasing formic acid, if disturbed.