Ants, round six and they keep coming back.

Sometime around mid or late November I noticed ants in one of our basement bathrooms. Not many, but within a couple of days they started to increase.
Though a first time for this room, we had numerous, frustrating issues with them during the summer upstairs in the house. I didn’t hit them hard this time as I assumed the onslaught of winter and a colder basement would slow them down. It didn’t.
So I got to work on eliminating them with all of the following: TERRO, ORTHO ant traps, RAID ant poison and a sugary BORAX mixture that I made. So the little buggers had plenty to choose from and they went crazy on it. Within a few days their numbers had diminished from dozens at any one time down to just a couple of ants. I though I was victorious.
A few days, maybe a week later, they started appearing again. So back to the above smorgasbord for them. Same results again, and within a week they were back.
This went on throughout December and right up to today. Probably the fifth or sixth round with them and they keep coming back.

What does it take to finally eliminate these ants? Do they have a new hatch every week or so, or are there that many different colonies in my house?

Btw, they were appearing behind the toilet and alongside the shower, so first off I put some sticky strips on the floor between the toilet and shower and also sprinkled cinnamon powder on the side of the shower base. All this to keep them contained, and it worked. They would not cross the cinnamon.

Is there a way to spray or treat outside this wall? Obviously they originate outdoors. There must be an ant colony right on the other side of the wall. I think you can buy spikes to sink in the ground. But, beware they may only move over a few feet and start up again. I would call an exterminator. Have them treat outside.

I’ve had similar problems with various ant species at our home and cottage and done considerable research and now fancy myself an experienced ant killer. So, my apologies in advance for the long answer but since this is the Straight Dope…

My learnings:

  1. If an ants are in your house in the winter, it means they have a colony against or inside your exterior wall. Normally colonies go dormant when it’s freezing out and then get active in the spring when they wake up and start to forage. If they’re inside now, they’re still active and foraging, which means they’re warm.

  2. Most poisons are low dose, the workers bring the poisoned food back to the colony for the queen to eat. Eventually the queen dies and the colony dies.

The “food” you’re offering must be attractive enough to compete with whatever else they have available so they keep eating it. To be most effective, you need to identify (google) what species of ant you have and research what they eat in your area and then tweak the poison mixture for max. appeal (see below)

  1. In general, the store “ant traps” & poisons rarely work. They are broad-species targeted and although they may have enough of the poisoning agent in them, if the species doesn’t like the flavouring agent, they don’t eat enough and it won’t work. Don’t waste your money.

  2. My best results are with a homemade mixture or a sweetener + boric acid + water. Boric acid (not Borax) is available in most drug stores, just ask.

The general starting ratio is: 100 parts water: 10 parts sugar: 1 part boric acid. So if you want to make 1 litre of solution you use: 1000ml water: 100ml sugar: 10ml boric acid.

For “sweetener”, sugar is usually used, but at our cottage I didn’t find it very effective (same results as you had). I was told that since we had a lot of maple trees in the area the ants likely preferred maple flavour. So I added a bit of maple syrup to the mix and it worked amazing.

Next thing you need to do is tweak the ratios, this is critical. You need to tailor the strength to your species: the amount of poison to kill a large carpenter ant is different than a tiny “sugar” ant.

Start with the basic recipe and then strengthen or dilute it until it works. Add a small measured amounts of boric acid to strengthen or measured amounts of water to dilute.

If the colony isn’t gone in a week or so, the poison ratio is too low, strengthen it. If it’s too strong, meaning the boric acid level is too high, it won’t work. It kills the workers before they return to the colony and feed the queen. If you see dead workers, there’s too much Boric acid, dilute it.

Also, if it’s too strong and kills off too many workers some ant species (like the red ants I had) consider the colony to be “under attack”. The queen then spits out new queen eggs which hatch and make new colonies. You now have a much bigger problem.

  1. For the “feeding stations” the best option I’ve found is to use the cheap lidded plastic “tupperware” tubs from the dollar store. Drill or punch holes in the sides about a 1/4 up. and fill them with cotton balls then the mixture, then add the lids. You can’t have enough of these, I lay down 20+. Ants forage in many directions, you want to cover them all.

I usually make a litre or two of the poison and then keep topping it up as it evaporates or gets eaten.

  1. Last two tips: I’ve found this 100% effective, but as you already know, there is no quick homemade solution. Be patient.

Write down the tweaking you do, so you know exactly the ratios that work for you. The ant colony will return at some point, (other ants in your area are always looking for good sites to expand to). This will save you re-doing the entire process.

Good luck.

I do the boric acid treatment for ants, too. I was told to use jelly or jam, and to stuff little gobs of the mixture into each end of little snipped-off sections of drinking straws. Cut pieces an inch or so long, use a toothpick to load each end, then you can tape the straws along their little ant highways … and away from kids/pets.

I’ve had good luck with boric acid, too. Spoonful of peanut butter in a ziplock, spoonful of boric acid. Smoosh around to mix, then snip off a corner of the bag to dispense. Lasts forever in the fridge. Don’t leave the bait in sunlight, big greasy mess.

Hands down Advian (available on Amazon) is the think to use. I know that an organophosphate pesticide sounds, well, scary, but the active ingredient is what is used in Frontline for dogs, so it’s toxicity to mammals is negligible. Follow the trail of ants to where they are coming out of the wall (you may have to put out something they like get enough to follow) and put down a bunch. Nothing else even comes close.

(post shortened)

It might help to verify the type of ant you’re dealing with. Are they carpenter ants, termites, or something else?

You’re probably dealing with multiple colonies. Foraging ants bring food (as well as poisons, acids, etc.) back to their nest to share. When that colony dies out, another colony may forage in the same area. You’ll have to treat each colony until they are all gone. The treatment is the same, but you have to have the patience to keep reapplying the treatments.

I’ve had success with a 50-50 mixture of borax and sugar, sprinkled under the radiators whence they seem to emerge. Just the powdered mixture. Maybe I’m lucky but it seems to work. We get them in the spring, however.

With something like 580 species of ants in North America, it seems a bit overwhelming to identify an ant. But, I believe it is this: small odorous house ant, Tapinoma sessile. It’s very small, to the point that if it is on a carpet, one has to get down on his hands and knees to really see it.

It is very possible that I have killed off one or more colonies in the past six weeks, only to have another colony come along, checking out the smorgasbord.
I also believe these are all living inside the house as winter has set in and any ants outside are hibernating, or doing whatever ants do in the winter.
Since the clean-up I did a couple of days ago they seemed to have disappeared, but since this afternoon they’re back again, with up to twenty or so at any one time.
So until I can get some Boric acid, I’ll continue with the current smorgasbord, but will strengthen the Borax mixture.

They just keep coming back.

I agree with this approach because you’re addressing the issue closer to or at the source. I had a similar ant problem in my kitchen and after two or three days of TERRO on the inside it appeared I was only feeding the ants because they kept coming. Once I checked outside, I saw a trail of ants crawling up the wall to my kitchen window. I sprayed the wall and ground with insecticide and the next day they disappeared.

BTW, TERRO was an effective ant product years ago but they changed their formula from arsenic as the active ingredient to a borax mixture which is less lethal. Apparently, the old formula also attracted companion animals (especially cats climbing onto counter tops/windows sills) with its sugar base.

(post shortened)

Patience, mon ami. The current blend seems to be doing the job. Just keep doing what you’ve been doing until they have all ceased to be, expired, gone to meet their maker, bereft of life, resting in peace, pushing up daisies, rung down the curtain, or joined the choir invisible.

Find the nest. Ants are trackable, you just need patience.

For a cheap, poison free solution, this has worked for me 100% of the time. Follow the ant trail as far as possible, then put a line of cinnamon across the trail.

Ants lay a chemical trail to follow, and they simply cannot follow a trail near cinnamon.