How to get rid of cockroaches in your Sydney kitchen (and stop them coming back)

It's 11 PM. You walk into the kitchen for a glass of water, flick on the light, and something black skitters behind the dishwasher. By the time you register the shape, it is gone. You stand there wondering if it was a one-off, or if there are twenty more behind the kickboards.

By the end of this guide, you will know exactly what species you are dealing with, how to hit them hard this weekend, and the signs that mean it is time to stop fighting and call in the big guns.

Identify your enemy: German vs native

Before you do anything, work out what kind of cockroach you actually saw. Killing a native Australian cockroach is a different game to killing a German cockroach, and getting this wrong is the number one reason DIY treatments fail.

The big black ones — the Australian or American cockroaches, 30 to 40 millimetres long — usually live outside in the garden, subfloor, or roof void. They wander in under a door gap looking for water. They are gross, but they are not an infestation in your kitchen. Sealing the gaps and laying a few perimeter baits sorts them out.

The small light brown ones with two dark stripes behind their head are German cockroaches. They are 13 to 16 millimetres long, they breed every few weeks, and they live exclusively indoors. If you saw a small one in the kitchen, you have a nest somewhere. German cockroach treatment requires a targeted approach, because a single female and her offspring can produce hundreds of roaches in a few months.

Cut their food, water, and shelter

Cockroaches need three things to survive in your home: food crumbs, condensation, and dark gaps to hide in. You can buy the most expensive bait on the market, but if you leave the water bowl out for the dog overnight, the roaches will drink that instead of eating your poison.

Start by clearing the kitchen completely. Wipe down the cooktop, sweep the floor, and empty the bin. You also need to deal with hidden moisture. A slow drip under the sink is a cockroach paradise, so check the plumbing connections and fix any weeping pipes. If your dishwasher has started smelling like a wet dog, there is a good chance there is stagnant water and grease trapped in the filter, which is exactly what roaches feed on. Cleaning out that dishwasher trap removes half their food source.

Next, pull the fridge and dishwasher forward and sweep behind them. Then slide them back. You are trying to eliminate the greasy dust layer they feed on.

Set the right traps and baits

If you have German cockroaches, skip the bug spray. Spraying a few strays does nothing to the nest, and the solvent just drives them deeper into your wall cavities. You need them to eat the poison and take it home.

Buy cockroach gel bait in a tube — Advion or Maxforce work well. Squeeze pea-sized dabs of gel into the dark, warm spots where roaches travel. Put them under the sink, behind the hinges of your pantry cupboards, along the back of the fridge compressor compartment, and near the motor of the dishwasher. Do not put bait in the middle of the floor or on food surfaces. Keep it out of reach of pets and kids.

Leave the bait alone for a week. You might actually see more roaches at first, walking around slowly in the open. That means it is working. They are coming out to die.

Did a job in a post-war brick semi in Marrickville last January. The homeowner had been spraying Mortein around the skirting boards for three weeks and wondering why the problem was getting worse. The spray had scattered the nest into the bedrooms. We spent twenty minutes placing gel dabs behind the microwave and under the fridge, and the colony was gone inside a fortnight. The spray was the problem, not the solution.

Try natural cockroach repellent (with realistic expectations)

If you only saw one large roach and want to avoid chemicals entirely, a natural cockroach repellent can work as a deterrent. A light spray of diluted peppermint oil along your window sills and door thresholds will stop the outside roaches from walking in. Roaches hate strong odours and will avoid treated areas.

You can also mix equal parts baking soda and sugar, leaving small jar lids of the powder in dark corners. The sugar attracts them, and the baking soda reacts with the acid in their stomachs and kills them. It is a messy solution and you have to clean up the dead ones yourself.

Honestly, whether natural repellents actually clear a German cockroach infestation depends on who you ask, but we have never seen it work for anything more than a handful of stray scouts. If you actually have a nest breeding behind your plasterboard, essential oils will not touch them.

Know the signs: When to call a pest controller

There is a clear line where DIY stops working. If you see cockroaches during the day, you have a heavy infestation. Roaches are nocturnal, so seeing one on your benchtop at 2 PM means the hiding spots are completely full and they are fighting for space.

Other red flags include finding dark droppings that look like coffee grounds inside your pantry, discovering egg casings behind the fridge, or smelling a persistent oily, musty odour in the kitchen. If you have laid gel baits and followed up with a thorough clean, and you are still seeing active roaches after two weeks, it is time to book a professional treatment.

A licensed pest controller will use insect growth regulators that stop the juveniles from breeding, alongside chemical barriers you cannot buy at Bunnings. They will also treat the roof void and subfloor if the colony has spread. Ask three pest controllers for a price and you will get three answers, but a proper internal and external treatment for a standard Sydney home usually sits around $250 to $350. We have seen it cheaper, and we have seen cowboys charge $600 for a quick spray. If a pest controller will not give you a fixed price over the phone for a standard three-bedroom home, hang up and call someone else.

If anyone in the household has respiratory symptoms, asthma, or allergies, consult a registered medical professional alongside the pest control steps below.

The Wenest take

In the homes we work in across the Inner West and Eastern Suburbs, the version of this that actually goes wrong is the wait-and-see approach. A homeowner sees one roach, ignores it, and three months later the entire kitchen has to be emptied for a full chemical treatment. The cheaper, faster fix is to act in the first 48 hours — identify the species, lay the gel baits, and starve them of water. If that does not work inside two weeks, call us. We will coordinate a licensed pest controller to hit it hard before it spreads to the bedrooms.

If chasing down pest controllers and waiting for quotes sounds like a headache you do not need, that is exactly why we exist. See how Wenest works.