How to get rid of cockroaches: what works, what doesn't

Cockroaches are the pest people most often try to fight alone — and the one where DIY most often fails. Not because the products are useless, but because the approach is usually wrong: spraying the roaches you can see does nothing about the population you can't. Here's how control actually works, from a licensed technician who treats Melbourne kitchens, cafes and homes every week.

Why you have cockroaches

Cockroaches need three things: food, moisture and harbourage — tight, warm cracks to live in. Every infestation traces back to that triangle. Food doesn't mean a dirty house: grease film behind a stove, crumbs under a fridge, pet food left out overnight, even cardboard glue is enough. Moisture is the one Melbourne homes underestimate — leaking dishwasher connections, condensation under sinks, damp subfloors. And harbourage is everywhere in a kitchen: cabinet hinges, appliance motors, the gap where the bench meets the wall.

Remove one leg of the triangle and the population shrinks. Remove two and it collapses. Every method below is really just an attack on one of those three legs.

Identify the species first

Australia has a handful of pest cockroach species, and they don't respond to the same treatment. German cockroaches — small, light brown, two dark stripes behind the head — live indoors near warmth and moisture and breed explosively; they're the species behind most serious kitchen infestations. American and Australian cockroaches — the big reddish-brown ones — mostly live outside in drains, gardens and subfloors and wander in. Oriental cockroaches — dark, almost black — favour cool damp areas like drains and subfloors.

Why it matters: a big roach that flew in from the garden is an exclusion problem. A German cockroach in a kitchen cupboard is a breeding problem, and it needs baiting, not a can of spray. Our cockroach identification guide covers each species in detail with photos of what to look for.

What actually works

Gel baits — the backbone of modern control

Professional cockroach control is built on gel baits: tiny dots of attractive food laced with a slow-acting insecticide. Roaches eat it, return to the harbourage, and die there — and because cockroaches eat their dead and each other's droppings, one bait dot can kill a chain of insects that never touched it. Baits work where sprays fail because they reach the 90% of the population hiding in cracks. Placement is the skill: dots go in hinges, corners, under benches — near harbourage, never on open surfaces where they dry out.

Starve and dry them out

Baiting works dramatically better in a kitchen that offers no competing food. Wipe grease, clear crumbs, store food sealed, empty pet bowls overnight, fix the dripping trap under the sink. You're not cleaning for cleanliness — you're making the bait the best meal in the room.

Seal the harbourage

Caulk the gap between bench and wall, seal pipe penetrations under sinks, and weather-strip external doors for the outdoor species. Every sealed crack is housing stock removed from the market.

Insect growth regulators and dusts

Professionals add growth regulators (which stop nymphs maturing into breeding adults) and dusts blown into wall voids and appliance motors — places gels can't go. This combination is why a professional treatment ends an infestation that months of DIY spraying only dented.

What doesn't work

Surface sprays kill the roaches you see and repel the rest deeper into harbourage — they can actually scatter a German cockroach infestation into new rooms. Worse, spraying near bait placements contaminates the bait and stops roaches feeding on it. Ultrasonic repellers have no credible evidence behind them. Bombing a kitchen with fogger cans coats open surfaces the roaches don't live on and misses the cracks they do. None of these attack the breeding population, which is the only thing that matters.

Keeping them away for good

• Nightly reset: benches wiped, dishes done, pet food up, bins closed — a cockroach kitchen audit happens at night
• Fix moisture: leaking taps, dishwasher connections, condensation under sinks
• Seal entry: door seals, drain grates, pipe penetrations — the big outdoor species walk in
• Cardboard discipline: delivery boxes are both harbourage and egg-transport; break them down and get them out
• Check second-hand appliances before they come inside — the classic way German cockroaches move house

Cockroach season in Melbourne

Cockroach pressure in Melbourne climbs with the temperature — activity picks up in spring, peaks over summer and early autumn, then the outdoor species push indoors as nights cool. German cockroaches, living entirely indoors with our heating, breed year-round regardless. If you saw roaches last summer, the cheapest time to act is spring — before this year's breeding season, not during it.

When to call a professional

Call when you're seeing German cockroaches (any at all — they never arrive alone), when you're seeing any species during daylight (a sign of crowding), when DIY baiting hasn't cleared it in a month, or when the property is a food business — where cockroach evidence is a compliance breach under the Food Standards Code, not just a nuisance. A professional treatment combines baits, growth regulators, dusts and proofing advice in one visit, with a follow-up to catch the hatch from surviving egg cases — and for businesses, the documentation your auditor wants. That's what our cockroach management service does across Melbourne, from single kitchens to audited food facilities.

Frequently asked questions

What gets rid of cockroaches permanently?

Gel baiting plus hygiene plus sealing harbourage — attack food, moisture and hiding places together. Sprays alone never do it because they miss the breeding population hidden in cracks. For established infestations, a professional treatment with follow-up is the reliable permanent fix.

Why do I still have cockroaches after spraying?

Surface spray kills the individuals you see and repels the rest deeper into hiding — and it can contaminate baits so roaches stop feeding on them. The breeding population in cracks and appliance motors never contacts the spray. That's why baiting, not spraying, is the professional method.

What keeps cockroaches away naturally?

Denying them food and water does more than any repellent: seal food, fix leaks, wipe grease, lift pet bowls overnight. Natural deterrents like bay leaves or eucalyptus have little real-world effect on an established population.

Are cockroaches dangerous to health?

They carry bacteria including Salmonella between drains, bins and food surfaces, and their droppings and shed skins are a recognised asthma and allergy trigger — a real issue in kitchens and for kids' health. They're a genuine health pest, not just an unpleasant one.

How long does professional cockroach treatment take to work?

Expect a dramatic drop within days and full knockdown over two to three weeks as baits work through the population and egg cases hatch into treated territory. A follow-up visit catches the stragglers — that's standard in our treatments, not an extra.

A1 Pest & Weed Control handles this for homes and businesses across Melbourne — licensed technicians, guaranteed results, and fast response: 0411 859 516 or get a free quote.