If it's where the counter meets the backsplash, it shouldn't be grouted, but caulked. I'd get a grout remover tool, (easy to use and not expensive) scrape out all the grout you can, then caulk that space.

Grout in that space has probably cracked, allowing them through, but the grout above that line is probably intact? They can't get through the caulk, but that won't solve the issue of where they are coming from and they just may find another portal. I've had good luck with ant traps on the outside of the house where they are entering. Different things work for different kinds of ants. You just have to find the right one. Good luck!

I'm dealing with the same issue: they are coming in through a pinhole in the caulk at the corner of the window. I had them coming in through another window last year and stopped that with borax at the base of the outside wall below the window. This year I can't see them climbing up the wall, but they are getting under the siding somewhere and then up to that window. I see the signs of their colony under the adjoining paver patio (little mounds of sand at the joints) -- I suspect that the entire area is involved in their excavations.

I am going to dab some caulk over the hole, then sprinkle diatomaceous earth all along the foundation. I have to look into how to eliminate them from under the patio pavers.

You've hit the nail on the head, you're playing whack-a-mole. You have an ant infestation to deal with and they're in the walls. If you block exit through the grout, they'll next come through the gaps of light switch plates or electrical socket plates, or at the gaps between floors and walls.

House ants are common in California where we both live and infestations are to be expected. We often get them in the late fall after the first rain. I'm not a DIY guy, I have a service I use. They use industrial strength stuff in inaccessible areas and pet and animal safe products elsewhere. It's important to find their point of entry (under the house if you have a crawlspace or at the perimeter otherwise) and hit that point heavy. Finding a nest is a bonus but usually not necessary as most products are treated as food by the ants and are taken back to the nest.

Good luck

I hate killing them too but we had to resort to Terro. That worked up until a year or two ago when they would invade our kitchen nonstop. They weren't even finding food but using our counters as a shortcut between their destinations on each side of our house. We put out the heavier duty outdoor Terro from Amazon and that finally worked. I haven't seen a single ant in about 2 months when before we had dozens every day for years.

Ants can do structure damage. Get rid of the colony not just one by one. Have an exterminator come check for the source.

You can try Diatomaceous earth in the kitchen it is not toxic or dangerous but does kill bugs.

Structural damage from ants is rare here. I can't imagine anyone would let an infestation last long enough for that to happen. When they're treated properly, the community is wiped out - until the next time another one comes along. More common is structural damage from termites.

Ages ago I tried using diatomaceous earth on an ant track. They treated it as an army would a minefield, they just went around it or found another place to come through.

I recommend a service too. Spend a few bucks and leave the pest control science to a qualified technician.

Funny story. I visited a customer a few years ago to give a paint estimate for baseboard, trim, etc. There was scotch tape applied along all the gaps. Yes. She was using it as an insect deterrent.

Carpenter ants do structural damage. The rest of the ant world have their own issues but that isn't it. Aggravation is what they usually cause. The trails they lay down with scent markers must be amazingly persistent as they will keep coming back for years. Follow them back to the nest.

As for ants, I think the best you an do is hold them back from your home and property. I've kept them out of our property a couple summers now, and I'm hoping for the best this summer. I would spray their trails and up the tree where they live, lifted rocks stepping stones spraying eggs. When take a walk, I still see them crossing my neighbor's sidewalk in a couple places, so I know the colony is still there. These ants don't like sweet baits, but if I put canned cat food out they like that. I mixed it with boric acid, but then they would not eat it. These are velvety tree ants...nasty things which bite and stink if you pinch them. The dog has even been bitten. Thanks for allowing me to vent!

We've had a few problems off and on over the last 20 years, but I could always follow the trail and figure out where they're coming in. Yes, they came through the outlet so I taped that up. :) I'm very reluctant to call a service for personal reasons, and will give Terro a try. They're coming from inside the wall so I'll have to leave the traps on the counter, darn it. Thank you all for your thoughts.

Some common ants are attracted to grease (fats, oils) also. The ones I am dealing with seem to have the sweet tooth -- I left a knife that I had cut watermelon with on the counter, and they were all over it.

Velvet tree ants are these guys, not to be confused with velvet ants, which are these guys:

Sjerin, I don't know if you've used Terro before but the ants will go nuts and absolutely swarm it. It will be very gross but they will disappear in a few days. I always warn people not to freak and to let it happen. :)

You can put them outside if you can find the trail into the wall.

Thanks, Chi. :). I had sprayed some bleach earlier and they hate that, so there are very few right now, darn it. The more that get to the Terro, the better for us! I think these are "protein" ants as they seem to have no interest in anything sweet; I too cut a watermelon on the counter and they had no interest. But they were all over a little sticky piece of cheese from mac and chz in the sink this morning. We shall see. I'm trying to take care of these pests now as my dd is getting married next weekend and we are busy.

Ugh, I see I left out the "r" in "through" in the title. Those kind of typos drive me nuts when I have to look at them again and again. Ha!

I had success pouring boiling hot water down the holes "tunnels" they use. Did it once and they never returned.

Boiling water is the ultimate non chemical treatment. I almost suggested it but I prefer to leave nature to nature commonly. You might have to do it more than once because you have to get the queen. Ants have their place in the ecosystem of the world so I prefer to divert.

You return from a weekend away and find ants crawling all over your kitchen. They're in your fridge, in the fruit bowl, into food not fully sealed in your pantry/cupboards, etc. You walk through the house and find them swarming in the bathrooms too.

What are you going to do and what does "diverting" them mean or do?

I try to use diatomaceous earth rather than chemicals, but find it works best if you find the colony and cover it and surrounding area with the DE.

Whenever I've used chemical killers, I've found they eventually come back and then the pesticide has no effect on them.

For a couple of years I dealt with repeated infestations of tiny thief ants, which love grease and any form of corn for some reason. They have multiple queens and are very difficult to eliminate. They changed what we keep on hand and how we store items. At one point it felt like we were living on an episode of "Infested."

A year or two ago, they disappeared and were seemingly replaced by the small red house ants. They stay less on paths, so are harder to "clean up." Thankfully they turn up less often.

Now, I can deal with an ant infestation in about 10-15 minutes and be done with it until the next possible one. Here's how I've come to deal with them:

Clean them up. Use an ammonia solution (where possible) to clean them up and eliminate their scent trails. Kill them all, and anywhere they are, clean.

Spray the entry point, or suspected entry points, with a pyrethrin based "pantry" spray. When it comes to the ants I have dealt with, this will stop the initial wave very quickly and for a minimum of months at a given entry point, even though the active ingredients supposedly do not stay active more than a few hours.

THEN, get some ant baits that are labelled for both sugar and grease ants. They are not easy to find necessarily, and you will need to read a lot of labels. We found some at Lowe's. It was a big name brand, but can't remember which one offhand. We did the research online so we knew what we were looking for. We had used terro years ago with great success. Our recent ants won't touch it.

Finally, check your house and yard and eliminate any ant colonies you can see evidence of out there. Shortly before our first small red ant infestation), we had a sizable hole a ways out in the yard. I stupidly left it because we had never had those ants in the house, and some of the lizards that live in our yard feasted on it daily. Some ant hills can be eliminated by pouring boiling water down them repeatedly for a few days. That would at least be a little safer for the lizards.

For the thief ants, we were told to spray the outside perimeter of the house, but that never seemed to have much affect. They finally disappeared after we got the sugar/grease bait combos- those may be what finally got their queens.

Finally, check your house and yard and eliminate any ant colonies you can see evidence of out there

This is my problem. I have never seen so many ants in the 27 years I have lived here! I have many plants in pots and planting bins (fruit tree, veggies, flowers) all around the property, and I am finding ants in most of them. This in addition to the colony under the patio. Is it because of all the rain last summer and this?

I’ve been having ants lately.. last night I poured terro on a small paper plate. I was up a couple times during the night and the plate was covered with ants. Today I have seen very few. Every once in awhile I see an ant hill in my yard.. I boil water and pour it over the hill. I know with all the rain we have had it has caused more ants out..

So far, so good....

We returned today to no ants. Yay!