Psocids

Advice leaflet about Psocids

Occasionally people find small grey or brown insects in their food cupboards and in foodstuffs such as flour, sugar and milk powder. It is usually assumed that the products themselves are at fault. This is not always the case. This information sheet will explain what these insects are and how to treat them.

What are Psocids?

Psocids - or booklice - which are often between 1 and 2mm long, might be found in dry foods. They are harmless insects and are not caused by poor hygiene, they are just as common in the cleanest of homes be they old or new. They prefer to live in dark, warm, humid places - such as the folds of packaging in food cupboards, and dislike light or disturbance. They feed on a wide variety of food products - such as flour - and also the microscopic moulds that develop in humid conditions. They may live for about 6 months during which the female may lay up to 100 eggs. Several independent studies have shown that the psocid species that causes the majority of problems are rarely found where food is produced.

Conditions

Psocids prefer areas with high humidity but can tolerate dry conditions for some days. The kitchen environment is likely to provide the conditions they need and fitted cupboards provide the darkness that attracts them. Some food products, including flour, naturally contain moisture. In warm conditions they can rapidly increase in number. This is most likely to occur during the summer months when temperatures are higher, leading to their discovery in the autumn.

Prevention of Psocids in the home

It is best to keep all dry foods in cool, ventilated cupboards. If this is not possible, make sure that your cupboards are always free from condensation and damp. If you notice that condensation occurs in your kitchen, particularly during cooking or washing, open your windows. If the problem is continual, it may be necessary to take additional precautions.

Packets of food that have been opened should be used up quickly and not pushed out of sight to the back of the cupboard. Psocids could increase here and move out to infest other, newer packages of food. NB. The 'best before' date can be affected by poor storage conditions.

Any potential hiding places should be sealed with paint or mastic. Many fitted kitchen cupboards are made from laminated chipboard and the surfaces that are not on view tend not to have a laminated finish. These unfinished edges can provide crevices for the psocids to hide in and should be sealed with a coat of paint or varnish.

Dry food can also get into crevices of cupboards and provide a food supply for psocids. Regular cleaning of cupboards is advisable but do not make the chipboard wet since this may encourage mould growth. Use of a vacuum cleaner is recommended, provided the contents are then immediately disposed of in an outside waste bin.

Control of Psocids in the home

If these prevention measures fail and you do discover psocids in your food, do not use an insecticide because of the danger of contaminating your food. Dispose of all visibly infested packages in an outside waste bin and thoroughly clean the cupboards using a vacuum cleaner, paying particular attention to crevices. If infestations occur in other parts of the house the same rules will apply.

It is important to make sure that when foodstuffs are replaced in cupboards that have been cleaned they do not reintroduce the psocids. Placing them in a deep freeze for 24 hours (enclose the products in a plastic bag) should treat dry goods. This will kill any eggs or juveniles that might be hidden in the folds of packaging. Labels should be removed from tinned food, bottles and jars to ensure that no psocids are hiding behind the paper. Use a felt tipped pen to label the bare containers. The freezer treatment is also suitable for books and other objects that you might suspect of harbouring eggs/individuals (enclose them in plastic bags).

Local Authority Service

The Public Health Department does not offer a treatment service for Pscocids.

Private Pest Control companies do offer a treatment service for Pscocids and you can find more information from your local telephone directory.