Booklice

Booklice (or psocids) are a common but harmless insect usually found in animal nests, tree trunk crevices, under bark or on leaves. They are also pests in the home as well as food manufacturing or retail premises.

What are psocids?

Psocids are tiny (about 1mm long) grey or brown insects. Food cupboards become infested with them, with the packaging from flour, milk, powder, sugar or semolina covered in them.

The food itself is not at fault. Psocids are not caused by poor hygiene, and in most cases the type of psocid found in domestic premises is not found in places where the food is produced.

Psocids are also known as booklice because some types of the insect are attracted to delicate materials such as books and furs. Here they can cause significant damage, but you do not normally find this kind in the home.

What attracts them?

They are attracted by the warmth and damp often found in kitchens, especially the darkness of kitchen cupboards. Some foods, including flour, naturally contain some moisture and it is here that psocids are likely to increase rapidly in number. They are also attracted by microscopic moulds that develop in humid conditions.

Bathrooms as well provide ideal conditions. Moisture in these and other rooms in the home can be caused by not enough ventilation

They are also known to swarm over new plaster which may still be damp. Again they do not cause any harm as they are attracted by minute bacteria and moulds.

Do psocids do any harm?

Psocids do not cause any direct harm in small numbers although large infestations contaminate foods.

How do I get rid of them?

Psocids are difficult to control with insecticides, because you may contaminate your food. If conditions for psocids remain after treatment, they can still re-infest.

Remove all contaminated food from the cupboards and place in an outside dustbin. You can then clean the affected cupboards with a dry cloth, or even vacuum - you should empty the contents of your vacuum cleaner into the dustbin as well.

Once the cupboard is clean it should be completely dried – it can be left empty and open to air, or a hairdryer could be used.

How can I prevent re-infestation?

As long as the kitchen and food cupboards are well ventilated and dry and you have not kept the food in these cupboards after its best before date, it should be possible to prevent a re-infestation of psocids.

Check packaging before buying to make sure that it is not damaged, and foods that are vulnerable - flour, semolina, etc - can be stored in washable covered containers.

Page last updated on 25 November 2011