Silverfish Can Mean a Moisture Problem

By Chris Williams on August 4, 2013.
Silverfish in duplex


We have a weird pest situation. I hope you can help. We live in a duplex; we have one half of the building and our neighbor owns the other half, separated by a common wall. We’ve had a terrible problem with silverfish and have had a pest control company treat twice, but we still have silverfish. Our neighbor admits that he has silverfish, too, but he won’t let anyone treat his place. Is there anything we can do?


Silverfish can be a very persistent problem. They have much in common with cockroaches. They are active at night and typically hide during the day in cracks, crevices, and wall or ceiling voids. Like cockroaches, silverfish move easily through voids and pipe runs, and can move from one unit to the other. You may very well be getting rid of the silverfish in your duplex, only to have them replaced by immigrants from your neighbor’s side.

You don’t say how old your building is or what condition it’s in. Silverfish are often an indicator of excessive humidity, moisture problems, and even mold caused by leaks, condensation, etc. somewhere in the building. If you’re not aware of a moisture problem, it could be in your neighbor’s duplex or in a common crawlspace. It will be difficult to control the silverfish as long as a moisture problem continues. Even once the moisture problem is resolved, it will take some time for the voids to dry out to a level that won’t support silverfish. Fans and dehumidifiers can speed up the process.

Try to find out exactly why your neighbor objects to treatment. If he has a problem with pesticide sprays, maybe he would consent to the use of baits where there would be no airborne vapors. Even sticky traps may help some. Maybe your neighbor would allow a pest management professional to inject insecticide into wall voids, or just treat the attic or crawlspace, if he is assured that his living spaces won’t be treated. At the very least, maybe he would allow an inspection of his home to check for moisture problems that can be repaired and which might make a big difference in the silverfish problem.

If you can’t get your neighbor’s cooperation, you should be able to keep silverfish out of the living areas in your home but it will require periodic insecticide treatments to insure that an insecticide barrier remains in place. Make sure that you don’t have moisture problems (including the roof) in your home. Caulk openings around pipes or lines, and any other obvious access points between the two units.

Photo credit: aj marx / Foter / CC BY-NC-SA



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