A woman in Woonona rang me in June after pulling a box of photo albums down from the top of her wardrobe and finding the covers grazed away in patches, like someone had gone at them with fine sandpaper. Half a dozen silverfish still doing laps inside the box. She spent the first two minutes of the call apologising for the state of the cupboard, which nobody needs to do. The cupboard was spotless. The house was just wet.
I get that call most weeks between May and August. Silverfish don't arrive in winter. Winter is when we shut the windows, stop airing the place out, and start opening cupboards we haven't touched since Easter.
Damp is the whole story
Silverfish want humidity, and an Illawarra winter hands it to them. Rain off the escarpment for a week straight, a house closed up tight, washing drying on the clotheshorse in the lounge room. And the one I find over and over in older places: an exhaust fan venting into the roof cavity instead of outside. You run a hot shower every morning and pump the steam straight up into the insulation, which is exactly the warm damp pocket they're after.
What they eat is starch. Book bindings, wallpaper paste, cardboard, photographs, the sizing in linen and cotton, dry goods once the packet's open. The Australian Museum's description of what a silverfish actually is is worth two minutes. They're one of the oldest insect groups going, wingless, doing this long before anything had wings to lose.
The ones you find are old news
Silverfish are slow. They live for years, they breed at nothing like the rate of a cockroach, and by the time you're finding them in three different rooms the population has been building quietly for a long while. So when someone tells me it started last month, it didn't. Last month is when they opened the cupboard.
That's also why they seem to come back. You wipe out the ones in the bathroom, and the ones in the wall cavity, the roof insulation and the dark under the bath carry on as normal. They never went anywhere.
Why the can under the sink misses
A surface spray puts product on the tiles, the vanity and the face of the skirting. Silverfish spend the day inside the crack behind that skirting, or up in the roof, and come out at night onto surfaces they barely touch. Bombs and foggers are worse value again, because the fog settles on open surfaces and never gets into the voids. Same reason cockroaches keep coming back when you chase them with a can, except silverfish are better hidden.
Naphthalene balls and cedar blocks don't kill anything either. They shift the problem a couple of metres to the left.
What actually shifts them
Fix the moisture first, or nothing else holds. Get the exhaust fans venting outside where they belong. Open the place up on the dry days, even in July. Check the subfloor vents aren't blocked by a garden bed or a stack of pavers, because a damp subfloor feeds silverfish, borers and half the other problems I see in older homes here. If a room never quite dries out, a dehumidifier over winter does more than any spray will.
Then clear the food. Anything you're storing goes out of cardboard and into sealed plastic tubs, especially photos, books and off-season clothes. Don't stack boxes straight onto a concrete slab in the garage either. The concrete sweats and the bottom of that box stays damp all winter.
Treatment is about placement rather than volume. We put a residual product into the cracks, the wall voids, the roof cavity and behind the skirtings, so it sits where they travel instead of where you happen to see them. Silverfish usually get rolled into a general pest treatment with the ants and spiders, because a home damp enough for silverfish nearly always has a couple of other freeloaders in it.
In the older weatherboard and fibro homes around Corrimal, Thirroul and Bulli, the damp and the silverfish come as a set, and the same conditions are what let rodents in over winter. Worth reading alongside rodent-proofing an older home, since you're already up on the ladder looking at the eaves.
If you're finding them in the linen press and you'd rather not lose another box of photos, give us a ring. We'll sort out where they're living rather than where you found them.
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