Ants colony under floor

Hello,

I live in Luxemburg right beside Germany/France and we have an ant problem.
They are Garden ants from what I can tell and they have a colony under the house, beneath the floor since flying ones have been coming up in the past week. Unfortunately, the small gaps/cracks they are coming out of between the wall and the baseboards are behind a giant cupboard. This makes it impossible for me to close the cracks without dismantling the thing spanning an entire wall.

This operation will take a long time, so I want to make sure the problem will be solved after the cupboard is back up again. I've read about TERRO® Liquid Ant Killer and boric acid powder on this forum. Boric acid powder sounds great since it would also kill those ants inaccessible otherwise underneath the floor in their nest. Furthermore, I have a Pattex which will harden and close all the gaps/cracks.

The plan so far:
Kill as many ants as possible either using products or calling a Renttokill service (would prefer to do it on my own if possible), dismantle the cupboard, kill, and clean. Finally, close everything up with Pattex.

The big question:
is will in your opinion killing them momentarily using products like TERRO® or boric acid powder and closing with Pattex be enough to prevent them from entering the house again in the long run? or does a professional rentokill have more permanent methods

Any tips, advice would be greatly appreciated. (If needed I can also send pictures to clarify the situation)

 

Dismantling a cupboard that large shouldn't be necessary to kill the colony, but if you want to caulk that area, then you'll have to do that.
Boric acid as a powder is repellent and will work against any baiting strategy. Boric acid makes the immediate area where applied toxic to insects, but they will avoid it too. It's not something I would ever use as a perimeter treatment, either inside or outside. It is good for blowing into a wall void as it will make that specific void toxic to future infestation. I don't know how you'd get it to the colony under a house/slab.

Terro is a good bait and is in fact boric acid based, but so mildly toxic that it isn't a repellent. I'd rather use the gel based baits that come in a plastic syringe applicator. You may be able to get the ants to forage to the gel bait by getting it behind/under the baseboard at each end of cupboard. They won't hesitate to forage that distance, once they find it. For example, I've used flat blades to lift up plastic baseboard/trim and inject underneath. Sometimes the corners give good access, if you can get to them. Might have to try various spots until you find one that accepts the gel without resistance. I've also drilled holes equal to applicator tip size into wall board just above the baseboard so that the gel can be injected pretty much on top of the wooden sill plate. Is there a way that you could drill/inject gel into wall voids from exterior? That way you'd be getting behind the cupboard, and they should find it quicker and easier.

Baiting rarely works fully the first time. Re-applications even weeks later or next year about this time are common, so don't think it a failure too soon. After first application, make sure that fresh bait is reapplied as needed, though that's a tough call if you can't see the bait. You can also put a dab of bait on wax paper squares, etc and set out if pets/children can be kept away. Multiple locations with smaller quantities are better than fewer locations with larger quantities, though we have to work within what the circumstances allow (large cupboard). You're probably getting the idea and strategy. The baits are low in toxicity so that the ants can take the bait back to the colony and feed them. If it was too toxic, they would die before accomplishing this, so don't expect fast results.

An additional idea would be to dig a slight trench right next to exterior wall in the soil perimeter along that wall, if the soil is accessible and pouring in a water based insecticide that will soak down. An insecticide that has "fipronil" as an active ingredient is ideal for ants/termites. Non-repellent, too. Not allowed to use it indoors though. Fipronil is also an animal flea treatment used in "Frontline" and generics.

I'm not sure of insecticide availability where you live though.

 

Drilling into the wall behind the cupboard is possible, that does seem to solve many of the problems in this particular situation. Only the left side of the cupboard of about 40cm faces a wall which would allow digging a trench on the outside, as you were suggesting,

Thanks a lot for your detailed reply, the information helps a lot.