Pest guide
How to Get Rid of Cockroaches
An honest home routine for clearing cockroaches: which of the two problems you actually have, what reaches them, what only scatters them, and the point where a tube of gel stops being enough.
Bait in the gap they sleep in beats spray on the shelf they walk over.
Almost every piece of advice on how to get rid of cockroaches skips the one question that decides the outcome: which cockroach are you looking at? There are two separate problems hiding under the same word. One is a small tan insect that breeds inside your cupboards and multiplies while you sleep. The other is a big dark insect that lives in a drain or a garden bed and walks in at night for a drink. The routine that clears the second one spreads the first one through your house.
This guide is written from the inside of Melbourne kitchens. It sets out the principle that separates methods that work from methods that only feel productive, rates the popular home remedies without flattering any of them, gives you a three week routine to follow, and says plainly where a householder runs out of road. You will find the rest of Tim's pest control guides for Melbourne homes written the same way.
Nothing here calls for gear you cannot buy at a hardware shop. Work through it properly and you will either clear the problem or learn something genuinely useful about what you are up against, and the last section explains how to read that result.
The principle
Why does spraying cockroaches make it worse?
A can of surface spray reaches the few cockroaches standing in the open and teaches every other one to move house. The bulk of the population is wedged inside gaps no droplet enters, the egg capsules are sealed off from anything applied to a surface, and the irritant gives the survivors a reason to spread into rooms that were clear.
The active ingredients in retail cans are flushing agents by design. They irritate an insect long before they kill it, so cockroaches bolt, and the ones that bolt far enough live to breed. You get a satisfying pile of bodies on the floor and a wider problem a fortnight later.
- Flushing agent
- An insecticide that makes insects run out of shelter rather than killing them where they rest. Useful to a technician who wants to see where a population is hiding, and the worst possible thing for a householder who wants numbers to drop.
This matters far more for the indoor species than the outdoor ones. A large cockroach that wandered in from a gully trap is one insect, and killing it with a can costs you nothing except the next one that follows the same route. A small tan cockroach breeding under your sink is part of a group, and scattering that group turns one treatable cupboard into a kitchen, a laundry and a hallway.
Melbourne flats make the scatter worse than a house would. Older blocks around the inner north and the bayside suburbs share wall cavities, plumbing stacks and service risers, so a population pushed out of one kitchen does not stop at your front door. Plenty of people describe treating their own unit twice before working out that the pressure is coming from next door.
So here is the scorecard. The test applied to every method below is simple: can it physically reach a cockroach sitting inside a dark gap, or does it only affect the ones already in the open?
| Method | What it really does | Worth doing? |
|---|---|---|
| Surface spray from a can | Drops whatever is in view and drives the rest deeper into voids and adjoining rooms | No, not against a breeding population |
| Total release fogger or bomb | Settles on open horizontal surfaces, leaves residue across benches, pushes insects into cavities | No. The worst option available |
| Gel bait in the gaps | Taken back into the shelter and passed around by feeding and grooming | Yes. This is the one that changes numbers |
| Supermarket bait stations | Right principle, far too few placements and usually sat on a shelf instead of in a gap | Sometimes, if you buy plenty and site them well |
| Boric acid dust | Kills insects that cross it and then groom, but a visible layer repels them around it | Thin films in dry voids only |
| Baking soda mixed with sugar | Takes out a few individuals while the sugar quietly feeds the rest | No |
| Bay leaves, cucumber peel, catnip | Nothing you can measure in a cupboard with a torch | No |
| Ultrasonic plug-in devices | Nothing in the independent testing backs what the packaging promises against cockroaches | No |
| Sticky monitor traps | Shows you which gaps are live and how numbers trend, without reducing them | Yes, strictly as a monitor |
| Bleach poured down a drain | Clears the smell for a day without touching the pipe run the insects came along | No, though keeping traps wet does help |
Before you buy a glue board: under regulation 62 of the Prevention of Cruelty to Animals Regulations 2019, setting a glue trap that an animal could get stuck to is prohibited in Victoria. Insect boards are lawful only where a cover, cage or barrier keeps animals away from the adhesive, so a bare sticky sheet left on a laundry floor is not an option here even though it is still sold online.
Two of those entries deserve a sentence more. Boric acid is a genuine insecticide and it is cheap, but it works by being walked through and swallowed during grooming, which means a thin invisible film in a dry void. Shake out a white drift under the sink and the cockroaches simply route around it. Diatomaceous earth behaves the same way and stops working altogether once it gets damp, which rules out most of a kitchen.
The method
How to get rid of cockroaches with gel bait
Put small spots of gel bait inside the gaps cockroaches already shelter in, use many more placements than feels sensible, and then leave them completely alone for a fortnight. Bait is slow on purpose, because an insect that dies on the bench never carries anything back to the group under the kickboard.
Gel bait works through the way cockroaches feed and clean themselves. One insect eats, returns to the shelter, and the active moves through the group in droppings and in the mutual grooming that goes on in a crowded gap. That chain is the whole value of the method, and it is why a fast knockdown product is worth less than a slow one.
- Find the gapsTorch and a mirror through the sink cabinet, cupboard hinges, the fridge recess and the kickboard line. Look for droppings like coarse pepper.
- Bait small and oftenSpots the size of a grain of rice, one every 20cm or so inside the gaps, not three big blobs on a shelf.
- Stop cleaning those gapsNo degreaser, no bleach, no spray anywhere near a placement. Residue puts cockroaches off bait for days.
- Wait and watchFourteen days without interfering. Count what you see each night so you can tell movement from wishful thinking.
The most common mistake is quantity. A home kitchen with an established population needs dozens of placements, not four, and they belong in the hinge pocket of each door, in the back upper corners inside a cupboard, along drawer runners, the warm housing behind the fridge and the dead space behind the kickboard. Gel on an open shelf is wasted: cockroaches cross open ground as fast as they can and feed where they feel safe.
Reading the result: expect sightings to lift for two or three nights as insects come out to feed, then fall through the first week and keep falling into the second. A curve that never bends, or one that drops and climbs again from a different room, is telling you the shelters were missed or something is still arriving from outside.
Placement safety is simple enough to get right. Inside a hinge gap, behind a kickboard or in an appliance recess, gel is out of reach of a crawling baby and a curious dog. On a skirting board or a benchtop it is neither safe nor effective. Read the label before you open anything, because the label sets the places a product may legally be used and the rate it may be used at.
One honest limitation. Retail gels are useful products, and they are still only half of what a treatment uses. The other half is an insect growth regulator that stops young cockroaches reaching breeding age, and that is the part a householder generally cannot buy. It is also the reason a home attempt can knock a population down and then watch it rebuild from a hatch six weeks later.
Food and water
Does cleaning and tidying really starve them out?
Cleaning on its own will not clear an established population, and it will slow one down enough to matter. Water counts for more than crumbs, because a cockroach copes for ages with nothing to eat and only days with nothing to drink. Taking away shelter does as much as taking away either, because a cockroach with nowhere tight and dark to rest does not settle.
Start with the wet things. A tap that weeps, a sink cabinet with a damp base, a pet bowl left out overnight, condensation behind the fridge and a dish rack that never dries are the reasons a kitchen holds a population through a dry Melbourne summer. Fixing a washer costs less than any product on this page.
Water first
Fix the dripping tap, dry the sink at night, lift the pet bowl before bed and mop up the condensation tray under the fridge. Thirst moves cockroaches further than hunger does.
Cardboard out
Corrugated card is shelter and transport in one. The flutes are exactly the right width, and the carton that arrives from a storeroom is one of the usual ways a population turns up in a clean home.
Close the gaps
Fill the holes where pipes pass through the cabinet base, seal the gap under the back door and put a cover on an open floor waste. Each one is a road as well as a bedroom.
Then take the easy shelter away. Flattened boxes stacked beside the bin, paper bags kept for later, a crate of empties in the laundry, newspapers under the sink and the pile of shopping bags in the cupboard are all prime real estate. None of that is a judgement on your housekeeping. Cockroaches are looking for a gap of a particular width, and clutter supplies thousands.
Food goes into sealed containers, which matters less for crumbs than it does for the bait. Gel has to be the most attractive thing in the cupboard. If an open bag of rice or a sticky honey jar sits beside a placement, the bait loses and you conclude it does not work.
A spotless kitchen with one weeping tap and a stack of cartons beside the bin is a better cockroach address than a messy one with neither.
It is worth saying clearly, because shame keeps people from acting: cockroaches indoors are not a verdict on how often you clean. The small indoor species usually arrives in a second-hand appliance, a delivery carton or through a shared wall, and a brand-new apartment offers it warmth, water and a hundred narrow gaps. Hygiene changes how fast the numbers climb and how quickly a treatment holds. It does not decide whether the problem starts.
What cleaning will not do is reach a group already living inside a dishwasher door or a fridge motor housing. Victorian health guidance pairs hygiene with registered products for exactly this reason, and it says plainly that a heavy infestation needs a licensed operator rather than a mop.
Two problems
Have you got the small indoor one or a big outdoor one?
Under about 15mm, pale tan, striped behind the head, turning up in numbers and with tiny wingless ones among them means a population breeding indoors. Over about 25mm, glossy and dark, seen one at a time after dark in a bathroom or laundry means an outdoor insect that came in for water. The two need opposite work.
Size sorts it in a second, and the presence of young sorts it beyond doubt. Tiny dark specks running from a kettle base or a microwave vent are nymphs, and nymphs mean eggs are hatching where you live. A single large insect at midnight means a doorway, a drain or a vent, and no amount of indoor baiting fixes a doorway.
A pair of dark stripes sits on the shield behind its head. Found in cupboards, appliance housings and the kickboard void. Numbers climb week on week. This is the hard one, and the one with its own routine in the guide to clearing German cockroaches.
Glossy brown to almost black, sometimes with pale markings behind the head. Lives in drains, subfloors, mulch and roof voids, comes in after rain or during dry spells, and is seen singly.
Specks like coarsely ground pepper at the mouth of a gap, plus a stale greasy odour inside a cupboard that has held them for months. Reading those marks is covered in the guide on cockroach signs and where they shelter.
For the big ones, the useful work happens outside. Lift the grate on the gully trap in the yard and look for the water seal: a dry or cracked trap is an open pipe into a sewer line, and that is the single most common source of large cockroaches in an older Melbourne house. Floor wastes in laundries and bathrooms do the same job indoors.
- Keep every trap wet. A seldom-used shower or laundry tub dries out and becomes a doorway, so run the tap for ten seconds a week.
- Fit a cover or a stainless grate over an open floor waste and replace a cracked gully trap grate rather than balancing a brick on it.
- Seal the collar where the waste pipe passes through a cabinet base or a wall, which is usually a finger-width hole stuffed with nothing.
- Pull mulch, leaf litter and stacked timber back from the wall, clear the gutters, and move compost away from the back door.
- Check the subfloor vents are clear and not blocked by garden beds, because a damp stagnant subfloor suits these species perfectly.
Drain work is where people waste money. Tipping bleach or caustic cleaner down a floor waste treats about 30cm of pipe and nothing beyond it, while the insects live along a run you cannot reach. Restoring the water seal and covering the opening achieves what the bottle cannot.
If you would rather try the low-toxicity route first, the honest ratings of the natural cockroach remedies people recommend will save you a few shopping trips. Two more rooms get their own write-ups because the detail differs: cockroaches in the kitchen and the surprisingly common case of cockroaches living in a car.
Where DIY ends
At what point should you hand it to a professional?
Call someone once you have baited properly for three weeks with no fall in numbers, once you are seeing tiny wingless ones, once they turn up in daylight, or once a second room joins in. Each of those four means the population is larger or more scattered than retail products are built for.
- Three weeks, no change. Either the shelters were never found or the bait is being refused because something repellent was used first.
- Nymphs everywhere. Specks smaller than a sesame seed mean eggs are hatching faster than you are removing adults.
- Daylight sightings. Cockroaches out in the open during the day usually means the gaps are full and competition has pushed them out.
- A second room. Bathroom, bedroom or hallway activity means the group has split, which doubles the search without doubling your reach.
Flats and townhouses deserve their own warning. Where the unit beside or above yours goes untreated, a kitchen can be cleared properly and still fill again inside a couple of months, because the pressure simply travels back along the pipework. Nothing failed. The source was never inside your lot in the first place, and the answer is units treated together rather than a fourth attempt at your own.
It is also worth knowing what a proper visit includes, so you can tell a thorough quote from a cheap one. The species should be named before anything is opened. Bait and dust should go into the voids and appliance housings rather than across open surfaces. A growth regulator should be part of the job. A follow-up visit should be named in the quote, not sold to you afterwards. Tim works that way on every cockroach job. He holds Victorian licence No. 86488, carries full insurance, covers the treated areas with a three month re-treatment guarantee, and reaches homes right across Melbourne and the surrounding suburbs.
If you have already set off a bomb or emptied a can, say so when you ring. Insects that have been pushed out of their usual gaps have to be tracked down again, and keeping that quiet only sends a technician looking in the wrong places. From there, cockroach control in Melbourne sets out how the treatment runs, and you can describe what you have been seeing and get a quote without committing to anything.
Questions
Questions people ask about clearing cockroaches
Does boric acid work on cockroaches?
Yes, within limits. Boric acid kills cockroaches that walk through it and then groom themselves, so it has a real place as an almost invisible film in dry voids and wall cavities. Laid on thickly it becomes a visible barrier they walk around, and it stops working once it gets damp.
Why are there more cockroaches after I sprayed?
Because the can reached the ones in the open and relocated everything else. Groups in the gaps and the sealed egg capsules were never touched, while the irritant sent the rest travelling along pipework and skirting into clear rooms. The cupboard looks better, the house is worse, and bait gets refused for days.
At what point is it worth paying someone?
After about three weeks of correct baiting with no drop in numbers, or straight away if you are seeing tiny wingless ones, daytime activity, or a second room involved. An indoor breeding population needs a growth regulator and a follow-up visit, and neither is sold over a counter.
How long does cockroach gel bait take to work?
Numbers usually lift for two or three nights, fall noticeably through the first week and keep falling into the second. The slowness is deliberate, because an insect that dies at the bait never carries anything back to the shelter. Nothing changed by day fourteen means the placements are in the wrong gaps.
Do cockroaches mean my house is dirty?
No. The indoor species usually arrives in a second-hand appliance, a delivery carton or through a shared wall, and a new apartment supplies all the warmth, water and narrow gaps it needs. Cleaning changes how quickly numbers climb and how easily a treatment holds, not whether it starts.
Are cockroaches a health risk indoors?
They can be. The Better Health Channel notes that cockroaches feed on waste and are believed to spread organisms such as salmonella, and that droppings and shed skins are linked to allergy. The practical answer at home is sealed food containers, wiped surfaces overnight and dealing with the population rather than the sightings.
Three weeks of baiting and they are still turning up?
Send a photo with your suburb and Tim will name the species, say what the treatment involves and give you the figure before anything is booked.
Reviewed October 2026 by Tim, licensed pest control operator (Victorian licence No. 86488). Cockroaches and health: Better Health Channel. Glue trap rules in Victoria: Agriculture Victoria. Product registration and label use: APVMA.