Big, shiny, reddish brown, and suddenly on the bathroom wall at eleven at night. Sometimes it flies. Nobody forgets their first American cockroach, but it's actually the easier cockroach to deal with.
The American cockroach is the large cockroach that lives in sewers, stormwater drains, manholes, septic tanks and damp outdoor spaces, and wanders into houses from there. Despite the name, it's found throughout the world's warmer areas, including all along the Garden Route. It's not usually a sign that cockroaches are breeding in your house. Most of the time, it's a sign that there's an open route between your drains and your bathroom or kitchen.
How to recognise them
- Size. Large, around 3.5 to 4 cm long, sometimes more including the antennae
- Colour. Shiny reddish brown, with a pale yellowish band around the edge of the shield behind the head
- Wings. Adults have full wings and can fly short distances, especially on hot, humid nights
- Young. Nymphs are smaller and wingless, reddish brown
- Egg cases. Dark brown, about 8 mm long, dropped or glued in sheltered spots rather than carried
Where they come from
American cockroaches live in large numbers in municipal sewers and stormwater systems and in damp places around buildings: manholes, drain gullies, grease traps, septic tanks, garden sheds, compost heaps and the bottom of piles of firewood. They come into houses through:
- Floor drains and shower drains without a working trap or cover
- Dry traps in basins or showers that haven't been used for a while
- Gaps around pipes where they enter walls
- Gaps under doors, especially at the back of the house
- Open windows on warm nights, when they fly towards lights
They're most noticeable in summer, after heavy rain that floods the drains, and in holiday houses where drains have dried out.
German or American?
The difference matters because the treatment is completely different. German cockroaches are small, light brown with two dark stripes, and breed indoors in kitchens. American cockroaches are large, reddish, come in from outside and drains, and are usually seen one or two at a time. A house can have both.
Are they dangerous?
American cockroaches walk through sewage and rotting material and then across surfaces in the house, so they can carry bacteria onto food and counters. They don't bite people in normal circumstances, but they're unpleasant and their droppings and shed skins can aggravate allergies and asthma.
How they're controlled
The aim is to cut them off at the source. We treat manholes, drain gullies, grease traps and damp outdoor harbourage with a residual product, place gel bait where they come in, and treat the entry points around the house. The most important part is often the simplest: making sure drains have working traps and covers and that gaps around pipes are sealed. Our cockroach control page covers the full treatment, and cockroach control in Mossel Bay looks at a coastal town where they're common.
What you can do
- Run water in unused showers, basins and floor drains every week or two so the traps don't dry out
- Fit covers or mesh to floor drains
- Seal gaps around pipes under sinks and behind toilets
- Keep the lids of manholes and gullies closed and in good repair
- Move firewood and garden rubbish away from the back door
- Use yellow outside lights near doors on summer nights
If you're seeing small, light brown cockroaches in the kitchen as well, deal with those first. They're the ones breeding indoors.
Holiday houses and blocks of flats
Two situations bring American cockroaches indoors more than any other. The first is a holiday house that has stood empty for months: the water in the shower and basin traps evaporates, and the drain becomes an open door. Running every tap and flushing every toilet as soon as you arrive, or asking the caretaker to do it once a month, makes a big difference, and our holiday home pest control visit includes a check of the drains. The second is a block of flats or a complex where several units share a sewer stack. There, the manholes and drains on the common property need treating, not just the unit where the cockroach was seen, so it's worth involving the body corporate.
Frequently asked questions
Where do big cockroaches come from?
Mostly from sewers, drains, manholes and damp outdoor spots. They get into houses through floor drains, dry traps and gaps around pipes and doors.
Can American cockroaches fly?
Yes, adults can fly short distances, especially on hot, humid summer nights, and they're attracted to lights.
Does seeing one big cockroach mean I have an infestation?
Not usually. American cockroaches usually come in from outside or the drains. Seeing small light brown cockroaches is the bigger concern.
How do I stop cockroaches coming up the drain?
Keep traps full by running water in unused drains, fit covers to floor drains, and have the manholes and drains outside treated.
Why do I see more cockroaches after rain?
Heavy rain floods sewers and stormwater drains, and the cockroaches living there move up and out, sometimes into houses.