This family of insects presents a
considerable risk to public health. They can carry diseases like polio,
salmonella, typhoid, dysentery and
food poisoning. Although not uncommon in domestic properties, they are well
known as pests in commercial kitchens. In these types of properties cockroaches
live in nooks and crannies, behind tiles, in drains and ducting, under
cupboards and units, holes in walls, around cookers and in service shafts.
Contamination of food occurs when they move from refuse or faecal matter to
food preparation areas. Cockroaches will eat anything they can find, from human
food and waste to leather, wallpaper and even each other.
Cockroaches are generally nocturnal
and like to live close to their sources of food and water. In large
buildings their lifestyle makes their
control difficult. The two main species found in the UK are:
The German Cockroach (Blatta germanica)
A better climber than the oriental
cockroach, yellowish-brown in colour at around 9 to 14mm in length
thrives in warm, humid areas like
kitchens and canteens.
Almost black in colour at around 20 to
24mm in length, the oriental cockroach is mainly found in cooler, less humid
environments than the german cockroach.
The number of eggs depends on the
species present. The eggs are laid in thick-walled resistant
capsules. In the case of the German
cockroach, these capsules are carried by the female until just
before they hatch. They are then
attached as per the other species to a surface near to a food source.
After several skin moults (known as
incomplete metamorphosis) the young develop into adults.
Development relies on the temperature
of their environment more than anything else (a drop in the
ambient temperature will slow growth).
The German cockroach is particularly
· Their small size
enables them to hide in the smallest of places.
· They have a short
development period and so reproduce faster than other species.
· The females protect
the eggs by carrying the capsules until just before they hatch.
· A large number of
eggs are contained within each capsule.
Effective control depends upon the
species present, so a survey or assessment of the area or building is needed to
help decide on the best methods of treatment. This is best carried out at
night, as this is when the cockroach’s maximum activity levels are reached.
Monitoring traps and sprays will help
identify the species. Skin casts, egg cases and droppings should
be looked for.
A good standard of hygiene is
important to control cockroaches. Preventing their access to food and
water will make the insects move
around more and so increase their contact with any insecticides. Good design and
building maintenance will minimise their hiding places (known as harbourages)
and help with ease of cleaning.