Australia has just over 400 cockroach species, but the cockroaches that infest homes are a small group of introduced pests. The main pest species are the German, American, Australian, smokybrown, brownbanded and Oriental cockroaches. German cockroaches are the hardest to clear. They breed the fastest and hide deep in kitchens, so one treatment is often not the end of the job.
Native cockroaches and house pests are not the same
CSIRO says there are just over 400 cockroach species in Australia, out of about 4,000 worldwide. The best known are the introduced pests that live in houses, restaurants and sewers. Most species hide during the day in crevices, under bark, rocks or logs, or in burrows.
So a cockroach under a garden log may be a native species. The ones that cause trouble indoors are the six pests below.
How to tell the pest cockroaches apart
Size, colour and where you found it do most of the work. These details come from the Victorian Department of Health guide to pest cockroaches.
- German cockroach. Amber, 12 to 15 millimetres long, with two dark stripes behind the head. Most infestations are in kitchens, under sinks, in cupboards and around fridges.
- Brownbanded cockroach. Small, 10 to 15 millimetres, pale glossy brown with light bands across the body. It hides up high, near ceilings, in furniture and inside appliances such as toasters.
- Oriental cockroach. 20 to 25 millimetres, dark brown to black all over. It is slow and usually stays at or below ground level, in damp subfloors and around drains.
- Smokybrown cockroach. About 30 millimetres, shiny dark brown to black. It lives in sheds, subfloors, mulch and drains, and is often drawn to lights at night.
- Australian cockroach. About 35 millimetres, dark brown, with yellow markings behind the head and along the edges of the front wings. It usually lives outside around shrubs, woodpiles and leaf litter, but can move into wall, roof and subfloor spaces.
- American cockroach. The biggest common pest, 35 to 40 millimetres, reddish brown with a pale yellow border behind the head. It lives in roof, wall and subfloor spaces and around sewers and grease traps.
A simple rule helps. Small and in the kitchen usually means German. Big and coming from a drain, the roof or the garden usually means American, Australian or smokybrown.
Padstow has denser housing around the station and Padstow Plaza. If small amber cockroaches with two stripes keep showing up under the sink in a Padstow unit, book cockroach control in Padstow and mention the stripes, because they point to German cockroaches.
Earlwood sits on hilly streets above the Cooks River. When large reddish-brown cockroaches keep climbing out of a floor drain in an Earlwood house, ask for urgent cockroach control in Earlwood that checks the drains, wall spaces and subfloor, not only the kitchen.
Why German cockroaches need more than one visit
German cockroaches are the most prolific breeders of the pest cockroaches, the health department says. Five facts explain why one visit is rarely the whole job:
- They breed fast. They can grow from hatchling to adult in as little as 40 days. They have three to four generations a year, with up to 40 young in each.
- They carry eggs. Adults often carry their egg cases. Young that hatch after the visit still have to meet the treatment before they die.
- They hide deep. They crowd into warm, damp cracks during the day and feed at night. Every crack, gap, void and surface they walk on needs treatment.
- They last without food. They can survive up to a month without food if they can reach water.
- A few is enough. A handful of German cockroaches can settle in a new place and breed to huge numbers.
This is why the department lists follow-up inspection and monitoring as one of the steps in good cockroach control. A second check finds the young that hatched after the first treatment, before they are old enough to breed.
Brownbanded cockroaches can be hard to clear too. They travel in furniture and luggage, and their hiding spots can be spread through a whole building. Roselands has a large shopping centre with houses all around it. If small banded cockroaches are turning up on high shelves and inside appliances in a Roselands home, book quick cockroach control in Roselands so the furniture, cupboards and bookshelves are checked as well.
Are cockroaches dangerous?
They can be a health risk. The Victorian Department of Health says cockroaches are serious pests because they live close to people, are found almost everywhere and can carry disease. They eat nearly any animal or plant material, including grease, paper and fabric. Some species also smear their droppings on surfaces to mark where they feed and gather.
Cockroaches are mostly active at night, so seeing them in daylight often means there are a lot of them.
Why are cockroaches in my house?
Cockroaches move in where they find food, water and shelter, such as leaking taps, crumbs, grease and open bins.
Each species also arrives in its own way:
- German cockroaches usually spread as stowaways in cardboard boxes and crates of food and drink.
- Brownbanded cockroaches are often carried in furniture, luggage and other household items.
- Australian and smokybrown cockroaches usually come in from gardens, woodpiles and mulch.
- American and Oriental cockroaches often come up from drains, sewers and damp subfloors.
Greenacre sits beside the Chullora industrial area. If German cockroaches start showing up in a Greenacre kitchen soon after cardboard boxes were brought in from work or a warehouse, book fast cockroach control in Greenacre and get the cardboard out of the house.
Find out the species first
If you are not sure which cockroach you have, photograph one next to a coin, note the room and the time you saw it, and share those details when you book household pest control in Bankstown. Knowing the species first means the treatment goes where that cockroach actually lives.