Pest Control
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Tiny, pale specks moving across a windowsill, a bookshelf or the inside of a food cupboard are unsettling to find. They are usually one of two things: booklice or mould mites. Neither bites or spreads disease, and both are a sign of the same thing, which is damp.
Booklice
Booklice (also called psocids) are tiny, soft-bodied insects, pale cream to light brown and around 1mm long. They have six legs, a relatively large head and long antennae, and they move quickly in short, jerky runs. The ones found indoors are wingless.
They get their name from feeding on the moulds that grow on the paste and glue of old book bindings, but they are just as happy on damp cardboard, wallpaper, the surface of damp plaster, and food packets in a humid cupboard. They develop quickly in warm, damp conditions, which is why numbers can build up fast.
Booklice are common in new builds and newly plastered rooms, where walls and floors are still drying out, and in kitchens and cupboards on cold outside walls.
Mould mites
Mould mites (the most common is Tyrophagus putrescentiae) are arachnids, not insects, so they have eight legs. At around 0.3mm they are barely visible one at a time. In numbers they look like pale dust that moves. They feed on mould, and will also infest stored food that is high in fat and protein, such as cereals, nuts, cheese and pet food.
In a stored food packet, a light grey or brown dust on or around the product can be a mix of live and dead mites, cast skins and droppings, and the food should be thrown away. Our guide to mould mites goes into them in more detail.
How to tell them apart
- Size. Booklice are about 1mm and you can see individuals. Mould mites are a third of that.
- Shape. Booklice have a distinct head and a longer body. Mould mites are rounder and pearly.
- Movement. Booklice dart in bursts. Mould mites crawl slowly.
A phone camera on full zoom or a magnifying glass is usually enough to tell. Small brown beetles in food packets are something else again: see our guide to weevils and other stored product insects.
Are they harmful?
Neither bites people or pets, and neither is known to spread disease. Mould mites can trigger allergy symptoms in some people, and handling heavily infested food can cause an itchy rash. Booklice spoil the food and paper they live on. The bigger issue is the mould itself: damp and mould in a home can affect health, particularly for people with asthma, allergies or other breathing problems.
How to get rid of them
- Remove what is infested. Bin affected food, and clear out damp cardboard, paper and anything mouldy that cannot be cleaned.
- Clean off the mould. Use a mould remover on walls and surfaces, following the product instructions, and wear gloves, eye protection and a mask. Never mix bleach with other cleaners.
- Dry the area out. Ventilate, keep the room evenly heated and run a dehumidifier if needed. Both booklice and mould mites die off once the air is dry.
- Empty and dry cupboards completely before restocking, and keep dry food in airtight containers.
- Fix the source of the damp. Repair leaking pipes, roofs and gutters, and use extractor fans when cooking and showering.
Keep books and papers in dry, ventilated rooms rather than in cellars, garages or cupboards on outside walls.
When to call us, and when to call someone else
If the damp has a building cause, such as a leak, failed seals or poor ventilation, a builder, plumber or independent damp surveyor is often the right person, and fixing it is what stops the problem. If you are not sure what you are looking at, or the numbers keep building after you have dried things out, send us a photo and we will tell you what it is and what will clear it.