Cockroaches

Cockroaches are found all over the world. There are more than 3,500 species of cockroach. The most common varieties in Australia include the German, American and Oriental cockroaches.

American cockroaches are large and black. German cockroaches are smaller and brown. Oriental cockroaches are medium sized and dark brown to black in colour.

Because cockroaches eat a wide range of food, including rotting garbage, it is believed that they spread a number of diseases to humans including salmonella and gastroenteritis. Recent studies have indicated cockroaches can also cause allergies.

A cockroach infestation can be treated with a combination of good hygiene practices and pesticides.

Identifying a cockroach

The characteristics of a cockroach include:

• oval-shaped body
• six legs
• long antennae
• flat and low-lying body
• fast-moving
• winged.

Cockroaches may spread a range of diseases

It is believed that the cockroach may be a reservoir for a range of bacteria including salmonella, staphylococcus and streptococcus. The cockroach can also harbour viruses such as the polio virus.

Like the household fly, the cockroach will eat virtually anything ranging from food spills on a kitchen floor to faecal matter. Ingested bacteria can survive in the cockroach's digestive system, sometimes for months or even years, and are passed in its droppings. Cockroaches will vomit and defaecate on food and it is thought that disease may be transmitted to humans when humans eat food contaminated by cockroaches.

Life cycle of a cockroach

A female cockroach lays between 10 and 40 eggs at a time. On average, the female can lay around 30 batches of eggs in her lifetime. The hatched young look the same as adult cockroaches, but smaller and without wings. Depending on the conditions and type, a cockroach can live for up to 12 months. These insects are cold-blooded and thrive in warm, humid conditions. This is why buildings in the northern parts of Australia are particularly prone to infestations.

Common hiding spots for cockroaches

Cockroaches prefer to live in kitchens and other food preparation areas, so they can feed off food spills and have access to water. Hiding spots for the household cockroach include:

• cracks in walls
• confined spaces, such as behind the refrigerator, in a pantry or underneath a stack of magazines, newspapers or cardboard boxes
• any furniture items that are generally left undisturbed
• kitchen cupboards
• below sinks
• around water heaters
• in drains and grease traps
• gardens.

Treating your house for cockroaches

The Pest Control Program at the Department of Health can offer information and advice on dealing with a cockroach infestation. Some general suggestions to eliminate cockroaches yourself include:

• Thoroughly clean the house at least weekly.
• Pay special attention to the kitchen and other food preparation areas.
• Clean regularly underneath the fridge, stove, toaster and other movable appliances.
• Empty the kitchen's rubbish bin regularly.
• Do not leave out pet food or food scraps in pet bowls.
• Clean up any food spills promptly.
• Make sure there are no sources of water such as a dripping tap, as cockroaches need a steady water supply to survive.
• Store food in sealed containers.
• Repair any holes, cracks or gaps in the walls, skirting boards and inside cupboards.
• Don't stack newspapers, magazines or cardboard boxes anywhere in the house.
• Keep compost bins screened and away from the house.
• Use appropriate insecticide and follow the manufacturer's instructions.
• Cockroach baits contain poison that a cockroach carries back to the nest, which may help kill the rest of the nest.
• Use physical traps, such as greased margarine tubs containing a smear of honey as the lure – cockroaches will climb in for the food, but be unable to get out because of the grease (or oil) on the tub.

Professional pest control

A qualified and licensed pest control operator can determine the type, source and extent of the infestation and use registered pesticides to control the cockroaches. Good hygiene practices, such as frequent house cleaning, should reduce the risk of further infestations.

Where to get help

• Licensed pest control operators
• Pest Control - Victorian Department of Health Tel. 1300 767 469