The cockroaches returned after a month. What went wrong
A recurrence almost always means that the wrong target or area was treated, or that treatment was incomplete.
The situation is typical: a treatment is carried out, there are no cockroaches for two weeks, and in the third week they return. The product is usually not to blame — as a rule, there are three causes, all of them procedural.
First: the oothecae were overlooked. The female carries and deposits an egg case whose shell is fairly resistant and protects its contents. Treatment kills active insects, but a new generation emerges from the oothecae two to four weeks later. This is why a single treatment almost never resolves the problem: a second one is needed two to three weeks later, timed precisely to this cycle.
Second: the source is behind the wall. If the problem affects the whole building, treating a single apartment produces only a temporary result. Cockroaches move through utility risers, ventilation ducts, and cable channels, and insects from neighbouring apartments occupy the vacated space. Without sealing utility entry points and fitting screens to ventilation openings, the problem will recur.
Third: incompatible methods were combined. A very common mistake is to lay out gel and immediately spray aerosol all around it. Gel works as bait: the cockroach must eat it and carry it away. A strong smell nearby repels cockroaches from the bait, so it stops working. These two approaches do not complement each other; they interfere with one another.
The effective procedure looks unexciting: remove access to water and food, seal routes between rooms, lay out the bait and leave it undisturbed, then repeat after three weeks. Unexciting — but this is what produces lasting results.
