Silverfish are persistent pests that are challenging to control. A thorough approach is the only method for success.
Silverfish are one of the most secretive of insects. In most cases they will only be noticed by customers when they have fallen into the sink or bath, or when moving boxes. Although most homeowners know little about them, they may be vaguely aware that they could damage their clothes and documents. Although pest managers will often include silverfish as one of the pests covered in their general pest treatment, if a customer has a specific problem with silverfish, successfully getting rid of them requires a more involved process and certainly an IPM approach.
Silverfish undergo incomplete metamorphosis, which means the young instars look like smaller versions of the adults, getting progressively bigger as they moult, with adults up to 18 mm (excluding tail). Silverfish are long lived, living from 2-8 years and going through up to 50 moults in their lifetime.
Silverfish are primarily vegetarians, preferring complex carbohydrates. This means they will eat cotton, paper, flour and cereal – materials with a high starch content. They have a particular passion for the glue in book bindings and wallpaper paste! However, they do need some protein content, so will eat insect carcasses too.
Perhaps critical to managing silverfish problems is that they like dark, humid, undisturbed areas. They need humidity levels of between 75-95%, as they don’t drink water but absorb it through their bums!
Bearing in mind their optimal environmental conditions and preferred food sources, silverfish are typically found in cardboard boxes, filing cabinets, drawers, wardrobes and subfloors. Although roof voids tend to lack humidity, silverfish can thrive in roof insulation.
As with any professional pest control treatment, a thorough inspection is required first and that’s never more important than when you are trying to get rid of silverfish. Whilst it is always important to ask where the customer has seen the silverfish, due to their secretive nature this should not be considered the only location where the silverfish are present. It is necessary to inspect all (empty) drawers and wardrobes, the roof void and subfloor (if present). The kitchen should not be ignored either, as they may be hiding in rarely accessed corners of the pantry or hiding in old cereal packets. The more challenging area to inspect will be home office areas or areas of stored documents and photos.
Generally, this is beyond the time that would be allowed for a silverfish treatment, but it should be emphasised to the homeowner that these areas should be checked – looking through files, books and photo albums individually. There’s no quick fix when trying to solve a silverfish problem.
In emptying wardrobes, drawers and cupboards, any silverfish spotted should be killed immediately, either with a quick spray or by squashing, before they have a chance to run off to a new hiding place. Any clothes in drawers or wardrobes where silverfish are spotted need to be washed at the hottest temperature their label allows, to ensure any silverfish eggs are destroyed.
Once these areas are free from obstruction, a residual surface spray can be considered with a suitable product, avoiding any surfaces that would be in direct contact with clothes or food. The use of powder in the roof void or subfloor is a good option, although the challenge is actually getting the treatment to where the silverfish may be hiding – under insulation or in boxes. Sticky traps could be used as monitors in previously known silverfish hotspots, to assess the effectiveness of the treatment.
To aid with the treatment and prevent infestations in the future, addressing any humidity issues is critical. The use of fans and air conditioning will certainly help. If the source of the humidity problem cannot be resolved, dehumidifiers in wardrobes and areas where silverfish have been found previously should be considered. Drawers, wardrobes and cupboards should be emptied at least once a year, with out of season clothes stored in well-sealed containers. Similarly, documents and foodstuff should also be stored in sealed plastic containers.
A number of consumer products are marketed as silverfish products – primarily containing camphor (which has some efficacy but would be limited in its range) or essential oils (of unknown efficacy). However, the reason the customer has contacted you is that they have either tried these products, which haven’t worked, or just don’t know how to get rid of the silverfish. Either way, a professional silverfish treatment is the way to go, but it’s not a quick treatment. If they have an infestation, a thorough inspection, targeted treatment and addressing conducive conditions is required to avoid the dreaded callback.
