A bloke in a unit block off Church Street in Wollongong rang me about cockroaches in his toaster. Not near it. In it, in the crumb tray, and when he pulled the tray out at night there were a dozen of them and most of them were small enough to go through the gap around the element.
He'd been spraying for about six weeks. Two cans. He was convinced the block had a problem and that the neighbours were filthy.
The neighbours were fine, as it turned out. The problem had arrived in his kitchen on a Saturday in a second-hand dishwasher he'd bought off Marketplace for a hundred and twenty dollars, which is roughly what the treatment ended up costing him to undo. The dishwasher itself was fine. The insulation blanket wrapped around the tub was not.
Two cockroaches, two completely different jobs
This matters more than anything else in this post, so it goes first.
If the cockroach you're looking at is big, dark, and moving fast across the hallway floor at eleven at night, that's almost certainly an Australian or American cockroach that has come in from outside. Drains, subfloor, garden beds, weep holes, under the back door. They're unpleasant and they're large and they are, genuinely, the easier problem. They aren't breeding in your kitchen. They're commuting.
If the cockroach is small, about the length of a fingernail, pale tan with two dark stripes running down behind the head, and you're seeing it on the bench or in a cupboard rather than on the floor, that's a German cockroach and you have a different situation entirely. The Australian Museum's page on the German cockroach calls it the hardest pest cockroach to get rid of, and that's not marketing copy on a pest control website, that's a museum being dry about it.
The stripes are the thing to look for. Two dark parallel lines on the shield behind the head. Nothing else common around here has them.
The reason the distinction matters is that the big ones are a barrier-and-entry-points job. Close the gaps, treat the perimeter, and you've largely solved it. The small ones are living inside your kitchen fittings, in numbers, and no amount of perimeter work touches them.
Why six weeks of spraying made it worse
Two things happen when you empty a can of surface spray at a German cockroach infestation.
The first is the obvious one, which I've written about before in the post on why cockroaches keep coming back: you kill the ones you can see, which is a small fraction of what's there, and the colony carries on.
The second is the one nobody tells you. A repellent spray doesn't just fail to reach them, it actively pushes them. Cockroaches avoid treated surfaces. Spray the visible ones on the bench and around the kettle and the rest of the population shifts: deeper into the cabinet carcass, up into the void above the overhead cupboards, along the conduit into the next room, and in a unit block, sometimes through the wall penetration where the pipework runs and into your neighbour's kitchen.
So at six weeks he had fewer cockroaches where he'd sprayed and more cockroaches in three new places. That reads as the spray working and the infestation spreading at the same time, which is exactly how people end up believing the building is at fault.
Where they actually were
I pulled the dishwasher out first, because he'd told me where it came from.
The motor housing was warm and there was a black tarry deposit along the underside of the insulation blanket, which is what a lot of them living in one place for a long time looks like. Shed skins in the fold. Egg cases, small pale ribbed things about the size of a grain of rice, glued into the seam.
Then the usual rest of it. The gap where the benchtop meets the splashback. Behind the hinge plates inside the cupboard doors. The recess under the sink where the waste pipe goes through the carcass. Inside the microwave's vent slots. The toaster crumb tray, obviously. And the one that surprises people every time, the rubber door seal of the fridge and the warm coil space at the back of it.
There's a pattern in that list and it's warmth plus a tight gap plus somewhere to drink. The Australian Museum notes they're sociable and gather in large groups near warm spots like water heaters, which in a modern kitchen means appliances. A German cockroach wants a crack it can touch with its back and its belly at the same time. That's the whole specification.
The maths of why it gets away from people
A female carries her egg capsule at the end of her abdomen until it's close to hatching, then glues it somewhere dark and safe. Each capsule holds somewhere between thirty and forty-eight eggs. One female, over a year, can be responsible for up to twenty thousand young.
I'm not putting that in to frighten anyone. I'm putting it in because it explains two things that otherwise seem unfair.
One: a "few cockroaches" in a kitchen is not a small problem that you have caught early. By the time they're out on the bench in daylight, the harbourage is full enough that some of them are being pushed out to forage in the open.
Two: it explains the second visit. The eggs inside a capsule are well protected, and nothing I put down reliably kills them in there. What kills the infestation is having something still working in the right place when that capsule hatches a couple of weeks later. Which is why the job is structured the way it is.
What the treatment actually is
Gel bait, into the gaps, in a lot of small placements rather than a few big ones.
That sounds underwhelming after six weeks of aerosol, and the first time I did one of these in front of a customer he asked me when the real part was starting. The gel is the real part. A cockroach feeds on it, goes back into the harbourage, and the effect carries through the group that lives there, including the ones I never saw and couldn't have reached. That's the entire mechanism, and it's why bait beats anything you can spray at them.
The placements go where they live, not where you see them: inside the cabinet hinge recesses, the underside of the bench overhang, the appliance voids, the pipe penetrations. Plus a residual treatment to the surrounding cracks and voids where it's warranted, and a direct go at anything visible. No fogging and no bombs. A fog in an open kitchen is the same mistake as the spray can, at a larger scale, and it drives them into the walls.
Expect to see more activity for a day or two. They come out to feed. Then it drops off sharply across the following week. The plain version of what's included is on the cockroach control page.
Your part is smaller than people fear. You don't need to empty the kitchen. What genuinely helps: don't clean the bait away, don't spray anything for a month because a repellent over a bait placement wrecks it, wipe the crumbs, fix the dripping tap, and take the pet bowl up overnight. Cockroaches need water more urgently than food, so a dry kitchen is worth more than a spotless one.
If you're in a unit or a townhouse
Be honest with yourself about whether it's only yours.
German cockroaches move along shared services: the riser, the common wall penetrations, the space under a shared floor. If the adjoining unit has them and isn't treating, you'll get a good result and then a slow drift back in about four to six months, and it isn't a treatment failure, it's a re-invasion.
The conversation to have is with strata or the agent, in writing, early. In my experience blocks where two or three units get done in the same fortnight stay clear, and blocks where one owner quietly deals with it on their own end up ringing me again in the spring. Tell them what was found and where. A written inspection note is usually what gets the neighbouring unit looked at.
Whoever applies the product at your place needs a current pest management technician licence from the NSW EPA, and you are entitled to ask to see it before anything goes into your kitchen.
The second-hand appliance thing
I'm not going to tell anyone not to buy a used dishwasher. Half the Illawarra furnishes kitchens that way and most of them are fine.
But check it in the driveway rather than in the kitchen. Pull the kick panel, look along the fold of the insulation blanket, and shine a torch into the motor space. You're looking for the black speckling and the shed skins more than for a live insect, because they'll be hiding while you're standing over it. Same check for a second-hand microwave, fridge or washing machine. Five minutes on the driveway.
The Church Street unit took two visits, nineteen days apart. He kept the dishwasher. I did tell him to get rid of the two remaining cans of surface spray, and I'm fairly sure he didn't, but he did stop using them, which was the part that mattered.
If you've got the small striped one in a kitchen anywhere from Wollongong down the coast and you're on your second can, stop spraying and give us a ring. The spraying is making the job I eventually do a bigger one.
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