You switch on the bathroom light at night and see a shiny silver creature vanish under the skirting board in a flash? Then you have silverfish. They are harmless, but unpleasant. And they tell you something about your home: silverfish are found almost exclusively where it's damp and warm. If you want to get rid of silverfish, you therefore need to tackle two things – the moisture and the places where they hide.
Contents
- Identifying silverfish
- Silverfish or grey silverfish?
- Why do I have silverfish?
- Are silverfish harmful?
- Getting rid of silverfish in 5 steps
- Home remedies put to the test
- When to call a pest controller?
- Preventing silverfish
Identifying silverfish
Silverfish (Lepisma saccharinum) are among the primitive wingless insects. Excluding their tail appendages, they are about 9 to 11 millimetres long, wingless and covered in shiny silver scales. They have two long antennae on their head and three tail bristles on their abdomen. They owe their name to their wriggling, fish-like movement.
Silverfish are nocturnal and very light-shy. During the day, they hide in cracks, behind skirting boards, under bath mats or behind furniture. If you see one in the light, there are often more nearby.
Silverfish or grey silverfish?
For some years now, a close relative has been appearing more and more often in German households: the grey silverfish, also known as paper silverfish (Ctenolepisma longicaudata). It is often confused with the silverfish, but behaves differently – and that matters when it comes to getting rid of it.
| Silverfish | Grey silverfish | |
|---|---|---|
| Size | approx. 9–11 mm | approx. 15 mm |
| Colour | shiny silver | rather brownish |
| Habitat | damp and warm: bathroom, kitchen, cellar | dry and warm: living areas |
| Humidity | approx. 75–97 % | approx. 55–80 % |
| Active | at night, very light-shy | during the day too |
| Damage | hardly any in normal numbers | possible to paper, books and wallpaper |
Grey silverfish mainly get into homes with cardboard boxes and packaging material from mail-order deliveries. Because they tolerate dry air, airing the room hardly helps against them. In the case of a grey silverfish infestation, the German Environment Agency (Umweltbundesamt) recommends calling in a professional pest control company.
Why do I have silverfish? The causes
Above all, silverfish need one thing: high humidity. According to the German Environment Agency, they thrive at a relative humidity of about 75 to 97 per cent; in cool, dry rooms they cannot reproduce. This is why silverfish are considered indicators of moisture.
Typical causes of silverfish in the home:
- bathrooms without windows or not airing for long enough after showering
- damp cellars, utility rooms and storerooms
- leaking silicone joints and gaps behind tiles and skirting boards
- water damage or cold areas of wall where moisture collects
- food within reach: crumbs, sugar, hair, skin flakes and dust
According to the German Environment Agency, a mass occurrence usually points to structural problems such as water damage or inadequate ventilation. If the insects persist despite airing, you should get to the bottom of the cause.
Are silverfish harmful?
Silverfish pose no danger to your health: they don't sting or bite. In normal numbers, they hardly cause any damage to objects either. They feed on starchy and sugary substances, but also on hair, skin flakes and even house dust mites. They're still unpleasant, though – and they show you that the air in that room is too humid. High humidity also encourages mould.
Getting rid of silverfish: 5 steps that really help
1. Reduce humidity
This is the most important step. After showering, cooking and drying laundry, air the room briefly and vigorously several times a day with the window wide open, instead of leaving it tilted open for long periods. Heat damp rooms sufficiently. An inexpensive hygrometer shows you how humid the air is: in living spaces, around 40 to 60 per cent is considered good. Windowless bathrooms benefit from an extractor fan with an overrun timer.
2. Eliminate hiding places
During the day, silverfish crawl into narrow gaps. Seal cracks along skirting boards, pipe openings and tiles, and renew porous silicone joints. Where that isn't possible, vacuum the cracks thoroughly on a regular basis – this is also recommended by the German Environment Agency.
3. Remove food sources
Wipe away crumbs and sugar residue, vacuum regularly – including under bath mats, cupboards and behind the toilet – and keep supplies such as flour and sugar tightly sealed. Cardboard boxes and old newspapers have no place in the bathroom or cellar.
4. Treat hiding places in a targeted way
In the case of an acute infestation, you can treat the insects' routes and hiding places specifically with Ollie Silverfish Spray. Spray it from a distance of about 30 centimetres onto skirting boards, joints and pipe openings, behind cupboards and under furniture. The spray is ready to use, water-based, almost odourless and leaves no sticky residue. Repeat the application every two to three days, let the surfaces dry and then air the room well. Keep children and pets away during application.
Use biocides safely. Always read the label and product information before use.
5. Monitor the infestation
You can check whether your measures are working with a simple trick: in the evening, roll up a dampened piece of newspaper, secure it with a rubber band and place it near the hiding places. The next morning, there are often silverfish inside – then dispose of the roll in a sealed bag. If there are fewer from week to week, you're on the right track. Alternatively, sticky traps along the skirting boards can help.
Home remedies for silverfish: what works?
- Scented oils such as lemon or lavender: Are supposed to drive the insects away. There is no evidence that they work reliably – and they do nothing to change the cause.
- Sugar or starch baits: Attract silverfish and are useful for monitoring, but don't eliminate the infestation.
- Cold and heat: Below 10 °C, silverfish are no longer active; above 35 °C, they die. This is hardly feasible for the whole home. However, you can freeze individual infested items, such as books in the case of grey silverfish.
When should you call a pest controller?
- if the numbers don't go down over several weeks despite dry air and treatment
- if they are grey silverfish and books, documents or wallpaper are affected
- if you suspect water damage or mould – in which case the cause should also be dealt with professionally
Preventing silverfish: your checklist
- Air rooms thoroughly with the windows wide open after showering and cooking
- Keep an eye on humidity with a hygrometer
- Keep joints and cracks sealed
- Regularly remove crumbs, hair and dust
- Don't keep cardboard boxes for long – especially not in the cellar
- Let bath mats and towels dry instead of leaving them lying around damp
Conclusion
Getting rid of silverfish mainly means: get the moisture out, seal the hiding places. If you lower the humidity permanently and treat the hiding places in a targeted way, you take away what the insects need to live. If they still stay, it's worth taking a close look at possible damp damage – or asking yourself whether they might be grey silverfish after all.
View Ollie Silverfish Spray · All products against silverfish · Find your pest
Source: German Environment Agency (Umweltbundesamt) – silverfish, firebrats and grey silverfish