German cockroaches: how to spot them and why they're hard to shift

If the cockroaches in your kitchen are small (about 12 to 15 mm), light brown and have two dark stripes behind the head, they are German cockroaches. They live and breed indoors, usually in kitchen cupboards, drawers and appliances, and they multiply fast: one female can produce up to 20,000 young a year. Good hygiene slows them down, but a targeted internal treatment is what stops an established infestation.

German cockroaches are the cockroach people most want gone, and the hardest to shift. Here’s how to tell them apart from the big outdoor ones, why they spread so quickly and what you can do about it.

How to identify a German cockroach

A WA Department of Agriculture fact sheet on cockroaches (distributed by SA’s Eastern Health Authority) describes the adult German cockroach as about 12 mm long, beige to light brown, with two dark stripes on the back of the head. Adults have wings but rarely fly. The Australian Museum calls it the smallest of the pest species and the hardest pest cockroach to get rid of.

The big, dark cockroaches that wander in on warm nights are different species. Most of them live outside, and an external perimeter treatment keeps them out. The German cockroach is the one that breeds indoors, so it needs a different approach.

Where they hide

German cockroaches want warmth, moisture, food and somewhere dark to hide during the day. According to the fact sheet and the Australian Museum, look:

• Inside kitchen cupboards and drawers, and on the undersides of drawers and benchtops
• Under and inside appliances: fridges, stoves, dishwashers, microwaves and toasters
• Around sinks, the dishwasher and anywhere with a slow leak
• In cracks and crevices in the pantry and bathroom cupboards
• Behind skirting boards and inside wall cavities, and near hot water systems

Why a few become many

The numbers are what make German cockroaches different. The female carries her egg capsule, holding around 30 to 48 eggs, until the eggs are close to hatching, then tucks it into a dark corner. Development from egg to adult can take as little as 45 days. The Australian Museum says one female can produce up to 20,000 young a year, and the fact sheet warns that a small infestation can become a major problem within a few months.

That’s also why surface sprays disappoint. They kill the cockroaches you can see, while the egg capsules and the ones in the appliances keep the population going.

How they get in

Seeing German cockroaches doesn’t mean you keep a dirty house. They mostly arrive by hitching a ride, in cartons, food containers and secondhand fridges, stoves and other appliances brought into the house. Once they’re in a warm kitchen with food and water, they settle in quickly.

What you can do

The fact sheet calls hygiene the single most important factor in managing cockroaches, because it limits the food and water that let them breed so fast:

• Don't leave dirty dishes, plates or food-covered benches overnight.
• Fix dripping taps and leaks, mop up puddles and seal around sinks.
• Store food, especially starchy foods like rice, cereal and potatoes, in tightly sealed containers.
• Keep rubbish in bins with tight lids.
• Check cartons and secondhand appliances before they come into the kitchen, and don't store cardboard boxes there.
• Clean under and around the toaster, microwave and other benchtop appliances, and fill cracks where they can shelter.

When to get a treatment

If you’re seeing German cockroaches regularly, it’s time to treat, and early is better because of how quickly they breed. Our cockroach control is a targeted internal treatment of the kitchen and the warm spots they breed in, plus external treatment of entry points, drains and sheltered harbourages. Heavy indoor infestations sometimes need a follow-up, and if yours does we’ll say so upfront.

Cockroach jobs are handled discreetly, for homes and for commercial kitchens and premises. Call Garry on 0403 018 325 for a free quote anywhere across the Barossa, Gawler and Adelaide.