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My apartment high-rise has been afflicted with ants in the past few years. The pest control technician says that it has become a common problem due to warming weather. Various things have been tried, and I am leaving this in their expert hands (or rather, the apartment management is). This question is not asking for further countermeasures.

When I find a place or pathway with many ants, I find that simply wiping with a damp cloth or vinegar doesn't keep them away for long. Wiping is supposed to disrupt their pheromone trails, but I only find somewhat lasting effects if I wipe with undiluted household bleach. I am pleasantly surprised that they stay away even after the bleach has dried. After some internet research, I found that bleach leaves behind a salt residue when dried. Is it the salt residue that keeps the ants away when wiping otherwise doesn't have lasting effect?

I've had another corroborative experience that leads me to suspect that salt residue has a repulsive effect on pharaoh ants. I keep a large beer glass of very salty water on hand because of the dental benefits of salt water rinse. I probably use too strong a solution, which likely has drawbacks (something I have yet to research). It is kept on top of the fridge. Around the glass is salt water staining. I never see ants around it, even though ants like water. I admit that this corroboration is not very strong, as I generally do not see ants on top of the fridge anyway

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    $\begingroup$ Although not familiar with the requirements set by biology SE this strikes me as being a suitable question for this site, since it is more about the sensorial perception and behavioral response of the ants, where the chemistry is important but relatively straightforward (and well addressed by the current answer). $\endgroup$
    – Buck Thorn
    Commented Aug 5, 2022 at 8:19
  • $\begingroup$ My bleach solution seems ill-advised, both because of the fumes and the adverse effects on laminate countertops. It looks as if I will have to get comfortable again with ants on my food preparation surface. $\endgroup$ Commented Aug 9, 2022 at 15:26

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It's likely that the bleach (hypochlorite), which is a strong oxidizer, is destroying the trails more effectively than the vinegar. The mechanism of action here is the organic pheromone molecules, known as monomorine-1 and faranal are broken down into smaller organic molecules through oxidation. This chemically disrupts the trail and it takes some time for the ants to re-establish it.

I'm no organic chemist, but the acetic acid in vinegar may be a good smell masker for us, but I don't think it will have any chemical effect on the pheromones.

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  • $\begingroup$ Thanks! I upvoted the answer. I have no idea how I can determine if it is the right answer. Maybe a biological chemist can weigh in with a more authoritative assessment? $\endgroup$ Commented Aug 2, 2022 at 23:21
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    $\begingroup$ @user2153235 You might get a better response if you request migration to the Chemistry SE, though there are some good biochemists on here too, who might be able to answer authoritatively. $\endgroup$
    – bob1
    Commented Aug 2, 2022 at 23:25
  • $\begingroup$ I will try that. Er....I was just about to cross-post. I then googled how to migrate. From what I read here and here, I suspect that I have to flag the question for closure and specify a migration as the reason. Unfortunately, I can't find a Close link/button. Maybe because I am the OP? $\endgroup$ Commented Aug 3, 2022 at 0:46
  • $\begingroup$ @user2153235 there should be a "Flag" link at the bottom of the text. I think that'll let you request migration, though I've never tried. $\endgroup$
    – bob1
    Commented Aug 3, 2022 at 0:56
  • $\begingroup$ Done. Thanks, Bob1! $\endgroup$ Commented Aug 3, 2022 at 3:27
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Another answer that is fairly speculative (though quite plausible, in my view) results from the fact that I am using undiluted household bleach. It leaves such a heavy salt residue. Information online is mixed as to whether and how much ants dislike salt. In my case, however, it may be that the salt simply provides a physical barrier against ants travelling up to the countertop from the seam between the sink and the countertop. I actually see white crustiness forming at the seams after jamming the bleach soaked rag along the seam.

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