Silverfish Killer Sprays

Along skirting boards, into cracks and crevices, behind and under the bath and basin, around pipework, inside cupboards, and in the dark damp corners silverfish travel. Treat the edges and gaps rather than open floor - that is where they actually move.

Check the label on the individual product, since not every spray is approved for food areas. Avoid food, utensils and food preparation surfaces, keep children and pets out until treated surfaces are completely dry, and ventilate as the label directs.

It depends on the product. Some are made for fast knockdown of insects you can see, so results show quickly. Others leave a residual deposit on treated surfaces to help reduce repeat activity over time. Check the label for expected performance, approved areas and reapplication guidance, or read our guide to knockdown, residual and IGR treatments.

Follow the reapplication interval stated on the label. In general, re-treat after cleaning or anything else that removes the deposit, and again at the first sign of new activity.

Not much quickly, but it adds up in the wrong places. They graze on starches and paper: book bindings and pages, wallpaper and the paste behind it, photographs, labels, cardboard, and natural fibres such as cotton, linen and silk. The marks are irregular grazed patches and ragged edges rather than clean holes, which is one way to tell them from moth or beetle damage. They do not bite, do not carry disease and do no structural harm, so the case for treating is about protecting stored paper and fabric.

Two different pictures. If sightings are unchanged, the spray has not reached where they shelter - silverfish live in wall voids, under baths and behind tiles, so treating into cracks and gaps does more than treating surfaces. If numbers dropped and then returned, the treatment worked and the damp brought them back.

Humidity. Silverfish survive where it is damp and disappear where it is not, so the durable fix is moisture rather than insecticide: fix leaks under baths and sinks, run the extractor, ventilate, and address damp in cellars or behind cold walls. Removing stored paper and cardboard takes away the food.

Possibly, and it changes what to expect. The common silverfish needs consistently humid conditions and fades away once a room dries out. Grey silverfish, sometimes called paperfish, tolerate much drier air, live longer and are spreading in UK buildings. The tell is persistence - if you have fixed the leak, improved the ventilation and they are still there months later, drying the room will not finish it on its own. Expect sustained treatment of the harbourage over a longer period rather than a quick result.

Two to three weeks with no sightings and nothing new on a sticky trap left set in the treated room. A trap left running after treatment is what tells you early if activity restarts.

If numbers are still climbing after a full treatment cycle and you have already dealt with the damp, if they have spread through several rooms rather than staying in the bathroom, or if they are getting into stored books, documents or archive material you cannot afford to lose. Persistent activity in a room you have dried out is worth a second opinion in itself, since it points to grey silverfish. Look for a qualified pest controller with BPCA membership.