Besieged by biscuit beetles?

Appearance and behaviour

  • The biscuit beetle (stegobium peniceum), also known as the drugstore beetle or bread beetle, is 2-3mm long and is mid to dark-matt brown in colour.
  • It is found in shops and domestic larders infesting a wide variety of foodstuffs such as flour, bread, breakfast cereals and other cereal products.
  • The female biscuit beetle lays its eggs either in foodstuffs or the surrounding areas. Around two weeks later the eggs will hatch and tiny larvae will emerge and infest foodstuff in the area, often penetrating packaging.
  • The larvae will live inside the packets of foodstuff for two to five months where they will continue to grow and moult. Once they have reached a full grown length of 5mm they find movement difficult and will construct a cocoon around themselves.
  • The pupal stage lasts two to three weeks then the adults may remain in the cocoon for a further two weeks before emerging. On emerging the adults disperse and live without feeding for up to eight weeks. Mating takes place soon after the adult has emerged and the female will then lay her eggs before she dies.

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The biscuit beetle causes serious problems for the food industry due to its widespread occurrence and its ability to breach most forms of food packaging.

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How to get rid of them

The Council does not offer a service for the treatment of biscuit beetles.

  • The source of the infestation should be traced and where possible eliminated.
  • Secondary sources of infestation such as birds nests and food residues should be removed as the biscuit beetle can use these in which to breed and re-infest new foodstuff.
  • To treat with insecticide, all food must be removed from the storage area and examined for contamination by larvae / insects.
  • Any contaminated food should be placed in a sealed plastic bag and disposed of.
  • A suitable insecticide (one for crawling insects) should be applied to the area and all cracks and crevices.
  • The area should be left for approximately 24 hours before thorough cleansing.
  • All remaining foodstuffs can then be replaced.

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  • Check cupboards regularly and use contents before their 'use by' dates.
  • Store vulnerable foodstuffs like flour in washable, covered containers.
  • Check food packaging before purchase to ensure it is undamaged.
  • Check the food on first opening, to ensure it is not infested.

Pesticides are available from hardware stores, make sure you read and follow the instructions before use.