No. That fear is real, but it is about a different kind of product than the one used on a professional treatment. It comes from the old way of doing this, not the current one.
The old way, and why it scattered them
Sprays and foggers are repellent. Roaches can smell them and move away from them, and that movement is the problem.
Broadcast spraying of insecticides will do more to scatter the cockroaches than it will to control them.
US EPA, Integrated Pest Management for Cockroaches in SchoolsThe same guidance is specific about why this matters if bait is already down:
Do not use this technique in rooms with cockroach traps, baits, or bait stations because roaches will avoid them after you have sprayed.
US EPA, Integrated Pest Management for Cockroaches in SchoolsThat is the same reason no one should layer their own spray over a professional treatment. It does not add protection. It teaches the population to avoid the bait that was working.
Scattering has somewhere to go
Pushing roaches out of one hiding place in an apartment building does not make them disappear. Apartments are not sealed boxes — wall voids, pipe runs and gaps at baseboards connect them. A population that scatters has somewhere to go, and the somewhere is not always your apartment.
The current way
Professional treatment now centers on gel, liquid and dust that do not repel roaches at all. They keep contacting it, keep carrying it back to where they live, and it works through the population rather than just the ones seen out in the open.
[Boric acid] acts as a stomach poison and is one of few materials that does not repel cockroaches, so they are not able to avoid it as they do other compounds.
US EPA, Integrated Pest Management for Cockroaches in SchoolsThe same source is direct about how long that keeps working, for a dust kept dry in a void:
If kept dry, it remains effective for the life of the building.
US EPA, Integrated Pest Management for Cockroaches in SchoolsThe two sections above are the government's own findings. This one is our practice rather than a rule. The liquid we apply along baseboards and cracks is built to keep working for roughly a month or two after each visit. The dust placed in wall voids and under appliances lasts much longer than that, because nothing in the room disturbs it.
What happens, on a timeline
There is no single number that fits every apartment, and any answer that promises one is a guess. What the government's own pest management guidance says is closer to this:
These materials take 5 days or longer to kill substantial numbers of roaches, and it can take weeks to suppress large populations to the point where none are seen.
US EPA, Integrated Pest Management for Cockroaches in SchoolsIn practice, most of what you will notice happens in the first few days to a week. A large, long-standing population can take longer to fully clear, and the trend over that time tells you more than any single sighting does.
If someone told you to buy your own gel first
Gel bait is the right product. It is what a professional treatment uses, so the advice is not wrong about the product.
What makes the difference is placement and communication. Bait has to sit where roaches already travel and harbor, not where it is easy to reach, and that is most of the result. Whoever treats the apartment also needs to know what you put down and where, so that two products are not competing in the same cabinet.
If you have already put gel down, that is fine. Say so, and say where. You can also ask what will be used in your apartment before the visit.
What to tell your building
If it has been more than a couple of weeks and activity has not changed at all, that is worth reporting on its own.
It has been about two weeks since the treatment and I am still seeing the same amount of activity. Is that expected, or should this be looked at again?
Pest control in an apartment building requires treatment, repairs, access and information working together. See how the pieces fit.
Send this to your building
If other apartments have the same problem, one message to your super or managing agent does more than ten calls about one unit. Copy this and send it however you already talk to them.
Edit it before you send if you want. No sign-up, nothing collected, and we do not see who you send it to.
Sources
- US EPA — Integrated Pest Management for Cockroaches in Schools (Document #909-B-97-001, produced for USEPA by the Bio-Integral Resource Center)
- 28 RCNY Chapter 54 — Indoor Allergen Hazards rules, including the §54-04(a) work practices (PDF)
- NYC Administrative Code §27-2017.8 — Integrated pest management practices
We are a pest control company working in Bronx and Brooklyn apartment buildings, and this is general information rather than advice about your apartment or your lease. Where our sources conflict with each other, we say so on the page rather than picking one quietly.