Bed bugs – least toxic control

Bed bugs infesting a house give off a nasty smell from ‘stink glands’. In these conditions, writes David Allen, the only solution may be to throw out the old mattress and take practical steps which avoid toxic chemicals.

There are 74 bug species belonging to the Cimicidae family that are known to feed on humans – the most frequently found being Cimex lectularius the common bed bug. Although they are not such a common nuisance today, bed bugs can still affect any household and are generally associated with low levels of hygiene and overcrowding. Other species such as the pigeon bug (Cimex columbarius) and the martin bug (Oeciacus hirundinis) found in martins’ nests predominantly feed on birds but can also feed on human blood. 

Biology
Bed bugs are wingless insects and as such move around by crawling or riding from place to place in clothing, luggage or other such transport. Distribution can be further exacerbated in places such as theatres and public transport, with infestations frequently occurring in hotels and other buildings where there is a high density and turnover of individuals. 
    Bed bugs are mostly found in bedrooms as they generally feed at night when the host is asleep. When not feeding they live in the bed frame or cracks and crevices around the room. They do not harbour in the mattress or bedding material. They are reddish brown in colour turning blood red after feeding. The adult reaches approximately 5mm in length and passes through five nymph stages over a period of time to 128 days. The female lays her eggs in batches of 10 to 50, they are white in colour and deposited on various surfaces with a thin glue. They take on average 10 days to hatch and can mature into adults within one to two months given ample food. The female is then ready to start laying eggs. The speed of development depends on temperature and food availability. Surprisingly, bed bugs can live longer without food and can go without feeding for up to 140 days; the adult typically lives for about 10 months but can survive for a year or longer in cool buildings. This sensitivity to temperature means bed bugs will start to die if temperatures drop below 9ºC or rise above 36ºC. However, modern buildings have created ideal conditions for the bed bug with central heating and easy access to adjoining properties being commonplace.

Non-toxic control
Bed bug bites generally cause the victim irritation and can lead to sleepless nights, some pain and swelling, although some individuals experience next to no allergic reaction at all. Bed bugs do not transmit any known disease. The bites often leave a hard whitish swelling and evidence of a heavy infestation will be the unpleasant smell created by the bugs ‘stink glands’. Further evidence of infestation is finding eggs, blood and faecal material on sheets and pillows. Strategies for ridding a bed bug infestation depend on which species is present. If it is a bat, pigeon or swallow bug then the source of the infestation may be a nearby nest or bat roost in the roof or under eaves. Removal of this source and blocking ways back into the house will help to prevent future infestations. However, it must be remembered that all species of bats are protected and it is an offence under the Wildlife and Countryside Act to remove or even block access to any bat roosting site. English Nature can give further advice on this issue.
    For the common bed bug it is wise to check possible harbourages in cracks in the bed frame, around door and window frames, behind pictures, fittings and loose wallpaper and in light fittings. Any holes, cracks or crevices must be washed to eliminate any eggs or waste that has accumulated and then caulked, painted or sealed. Bed bugs can easily climb surfaces like wood so to prevent them from gaining access to a sleeping host, barriers can be put in their way. Examples of this are the use of petroleum jelly on the legs of the bed, putting the legs inside smooth metal jars and moving the bed away from any surfaces such as walls. Mattresses should either be replaced or steam-cleaned and bedding washed at a high temperature, making sure to transport bedding in an enclosed plastic bag to stop contamination of other areas. Exposure to hot and cold temperatures is a useful part of an infestation reduction policy, and raising temperatures to between 36ºC and 37ºC for an hour or so will probably eliminate an infestation, and prolonged exposure to temperatures of 0ºC to 9ºC will also kill off adults in a matter of hours. 

Chemical control
Chemical control strategies often start by flushing bed bugs out from their hiding places by use of a natural or synthetic pyrethroid based aerosol spray. This is then followed by use of other insecticides inside the premises, including the treatment of beds and other furniture. Active ingredients approved for use against bed bugs in the UK under the Control of Pesticides Regulations 1986 (COPR) are the following organophosphates: chlorpyrifos methyl, diazinon, fenitrothion, iodofenphos, pirimiphos-methyl and trichlorfon; and carbamates, bendiocarb and propoxur. These groups of chemicals act as nerve poisons which kill by inhibiting the nerve enzymne cholinesterase which disrupts the nervous system. More than half of these actives will have their licences revoked as part of the UK Health and Safety Executive (HSE) review of all anticholinesterase compounds. This process began in September 1998 when data call-in letters were sent to approval holders. Because of lack of support the following substances chlorpyrifos-methyl, diazinon (which shows evidence of mutagenicity and evidence of embryotoxicity), iodofenphos, trichlofon and propoxur (a suspected human carcinogen) have had their licences revoked(1,2).
    The synthetic pyrethroids alpha cypermethrin, bioallethrin, bioresmethrin, cypermethrin, deltamethrin, d-phenothrin, permethrin, resmethrin, s-bioallethrin, tetramethrin and the OPs trichlorphon and fenitrothion are suspected of being endocrine disruptors. Endocrine disrupting chemicals may affect the balance of normal hormonal function of animals and are suspected of contributing to the decrease in male fertility, female reproductive problems, increases in prostate and breast cancer, and behavioural and developmental problems in children(3). The German Federal Environment Agency suspects deltamethrin of affecting sperm and the placenta and dimethoate of affecting sperm and prolonging pregnancy(4).
    The botanicals registered for use in the UK (pyrethrins and pyrethrum extract) are the only pesticides that are not suspected endocrine disruptors or anticholinestease compounds.

Comment
If the physical control techniques outlined above are followed then the use of pesticides should prove unnecessary. Recent reports of bed bug resistance to certain groups of active ingredients underlines the importance of non-toxic methods. Pest Control Operators will usually try a product from another group of actives until the problem is solved or they have run out of options(5). Most of these chemicals are skin and eye irritants so use of them could replace one itch with another and the presence of pesticides in the bedroom, often on the bed and mattress is not advisable. 

The main sources for this article were:

• Common-Sense Pest Control: Least-toxic solutions for your home, garden, pets and community, Olkowski, W., Daar, S. and Olkowski, H., Taunton Press, 1991, 183-186.

• Insect pest factfile, biology and control, AgrEvo Environmental Health, 1998, 11-12.
  1. PAN UK Active Ingredient Database, 1999.
  2. List of active ingredients that have been approved for use against bed bugs, provided by the Health and Safety Executive 13/05/99 and personal communications 10/02/2000.
  3. Environmental endocrine disruptors, A handbook of property data, Keith, L. H., John Wiley and Sons, Inc., 1997, 1232pp.
  4. ENDS Report 290, March 1999, p28.
  5. Pest Control News, February 1999, No.49.

[This article first appeared in Pesticides News No. 47, March 2000, p21]