Cockroaches in Winnipeg: biology, behaviour and control

What we're dealing with

Three cockroach species turn up in Winnipeg buildings, and they are not interchangeable. Getting the identification wrong means getting the treatment wrong, because their harborage, their movement and their tolerance for cold are entirely different.

German cockroach (Blattella germanica) is the one that matters. Tan, 12–16 mm, with two dark parallel stripes running back from the head. It lives indoors, exclusively — it has never been found in a natural habitat anywhere on earth. This is the species behind the overwhelming majority of Winnipeg infestations.

American cockroach (Periplaneta americana) is far larger at 35–40 mm, reddish-brown, with a pale figure-eight marking behind the head. In a prairie city it lives in infrastructure rather than kitchens: drain stacks, steam tunnels, boiler rooms, commercial basements.

Oriental cockroach (Blatta orientalis) is glossy near-black, 25–30 mm, slower moving, and strongly associated with cool damp — floor drains, sumps, crawl spaces.

That history is not trivia. It explains the animal you are dealing with: a species that has spent two millennia being selected purely for its ability to live alongside humans in heated, plumbed structures. Every trait that makes it difficult — the tight harborage preference, the reproductive rate, the speed with which it evolves around our chemistry — is the product of that selection.

Life stages and cycle length

German cockroaches are hemimetabolous: egg, nymph, adult. There is no pupal stage and no larval form. Nymphs look like small wingless adults and occupy exactly the same harborage, which matters because a treatment that only reaches adults leaves the majority of the population intact.

The reproductive arithmetic is what makes early intervention worth so much. A single mated female entering a building in January, with all offspring surviving, has a theoretical descendant population in the tens of thousands within a year. Real-world survivorship is far lower, but the direction is the point: cockroach populations do not plateau on their own.

Development is temperature-dependent. Below about 15 °C, development effectively stops. This is why unheated garages and detached sheds in Winnipeg do not sustain German cockroach populations, while a heated apartment block does so year-round regardless of what January is doing outside.

Harborage and foraging

German cockroaches are thigmotactic — they seek surfaces touching their bodies on multiple sides. A crack that contacts both the dorsal and ventral surface is preferred over an open space, however dark. This single behavioural fact drives almost everything about how a building should be treated.

Harborage clusters around three requirements met simultaneously: warmth, moisture, and food within a short foraging radius. In practice, that is:

• Refrigerator and freezer motor compartments — consistently the highest-density harborage in a residential kitchen
• Dishwasher and stove voids, particularly around insulation and wiring runs
• Cabinet corner voids, hinge recesses, shelf-bracket holes and drawer runners
• The void behind and beneath the sink, around plumbing penetrations
• Motor housings in coffee makers, microwaves and toasters
• Wall voids at plumbing chases, which is the route between units in a multi-unit building

Foraging radius for a well-fed population is short — often under three metres from harborage. That is useful diagnostically: a heavy population sighted in a bathroom usually means harborage in that bathroom, not migration from the kitchen. It also means bait placement matters enormously. Bait placed two rooms from harborage will be found eventually; bait placed inside the harborage is found within hours.

They can pass through a gap of roughly 1.6 mm — about the thickness of two stacked coins. Sealing "the obvious gaps" therefore does very little on its own.

Social dynamics: not a colony

This is the most common misconception we correct on site. A cockroach infestation is not a colony. There is no nest, no queen, no caste structure, and no central point that can be destroyed to end the problem. Anyone offering to "find the nest" is describing an ant or wasp job.

What cockroaches have instead is gregarious aggregation — individuals cluster in response to an aggregation pheromone deposited in faeces. The pheromone accumulates where cockroaches already rest, which makes existing harborage progressively more attractive over time. An established infestation is therefore chemically self-reinforcing, and cleaning faecal deposits from harborage has a real, measurable effect independent of any insecticide.

Nymphs practise coprophagy and necrophagy — they eat adult droppings and dead individuals. In an untreated building that is how gut microbiota transfer between generations. In a treated building it is the mechanism that makes bait work: an adult carries the active ingredient back to harborage, dies, and its body and droppings deliver a lethal dose to nymphs that never touched the bait station. This is secondary and tertiary mortality, and it is the whole reason gel bait outperforms spraying.

Behaviour

German cockroaches are nocturnal, with peak activity in the first few hours of darkness. Daylight sightings are diagnostically important: they generally indicate either a population large enough that harborage is overcrowded, or a recently disturbed harborage. When a client tells us they are seeing cockroaches during the day, we scope the job larger.

They are omnivorous scavengers with a strong preference for starches, sugars and fats, but they will consume soap, toothpaste, glue, cardboard, leather and hair when preferred food is absent. Starving them out is not a viable strategy in any real building.

They are also capable of olfactory learning — they associate odours with food and with aversive experiences, and modify foraging accordingly.⁵ That capacity is directly relevant to bait failure, discussed below.

The health case

Cockroaches mechanically carry pathogens across surfaces, but the better-documented risk is allergenic. The New England Journal of Medicine reported in 1997 that among inner-city children with asthma, the combination of cockroach sensitisation and high bedroom allergen exposure was associated with significantly increased hospital admissions and asthma morbidity — a stronger effect than dust mite or cat allergen in those cohorts.⁶ Follow-up work established a clear dose relationship between bedroom Bla g 1 concentration and sensitisation rates in children aged four to nine.⁷

One finding deserves emphasis for anyone managing rental housing. A National Cooperative Inner-City Asthma Study intervention applied professional extermination plus resident education across 265 homes; allergen burden fell significantly at two and six months, then returned to or exceeded baseline by twelve months.⁸ A single treatment round in a connected building does not hold. Sustained programs do.

Where in Winnipeg

Cockroach distribution in this city follows building type and management quality far more closely than it follows geography. It is not a question of which neighbourhood is affluent; it is a question of whether a structure is heated, connected, and serviced.

The trend is well documented. CBC reported in November 2023 that Winnipeg cockroach populations had been rising for roughly eight years, with one local operator's treatment volume doubling from about 1,000 to more than 2,000 jobs in a single year.⁹ A separate operator reported inspecting more than 2,800 sites in 2022 and over 3,700 in 2023.¹⁰ The provincial spokesperson quoted in the same CBC reporting noted seven food service closures due to infestation that year, against one in 2022 and none in 2021.⁹

Where they concentrate:

• Multi-unit residential. Apartments and condominiums are the dominant setting, because shared hallways, service chases and large crawl spaces allow movement between units.⁹ Treating a single suite in a connected building is money spent on a problem that walks next door.
• Social and subsidised housing. Documented repeatedly in Winnipeg — including a downtown Manitoba Housing complex on Kennedy Street where traps in hallways and stairwells filled alongside those inside suites,¹¹ and a 2024 case in which a family left a Manitoba Housing apartment over an infestation.¹² This is a maintenance-and-coordination failure pattern, not a tenant behaviour pattern.
• Rooming houses and older converted stock, concentrated in the older core, where units are subdivided and building services are shared.¹³
• Food service, across the whole city, wherever warmth, moisture and organic residue coincide behind equipment.

Single-family detached housing in newer suburbs is the least affected category — not because those households are cleaner, but because a detached structure has no shared wall through which a population can arrive.

Natural control factors

Very little constrains German cockroaches indoors, which is precisely why they are a pest.

• Cold. The one genuine limit. Development stops below roughly 15 °C and sustained sub-zero exposure is lethal. Winnipeg's climate is hostile to them outdoors and irrelevant to them indoors — the species simply does not go outside here.
• Desiccation. They require free water and will die faster from lack of it than lack of food. A genuinely dry building is a poor habitat, which is why fixing a slow under-sink leak does more than most people expect.
• Cannibalism. Density-dependent, and it does suppress populations at extreme crowding — but only at densities well past the point anyone would tolerate.
• Predation and parasitoids. The parasitoid wasp Aprostocetus hagenowii attacks oothecae and has been trialled as a biological control, largely against Periplaneta. It is not a practical residential option in this climate.
• Entomopathogenic fungi. Metarhizium anisopliae has genuine laboratory efficacy and appears in the research literature as a candidate. Field performance in occupied buildings has been inconsistent.

The honest summary: there is no natural control factor you can deploy in a Winnipeg apartment that will resolve an established infestation. Sanitation and moisture correction change the carrying capacity of the building, which is real and worth doing — but they suppress, they do not eliminate.

DIY: what works, what backfires

We would rather tell you what to try than have you spend $200 at a hardware store making the job harder for whoever comes next.

Boric acid deserves a qualified mention. It genuinely works as a stomach poison and resistance to it is minimal, because it acts physically rather than on a neural target. But it must be applied as a barely-visible dust in voids. The thick white line people typically lay down is visible to the cockroach and simply gets walked around. Applied badly, it is worse than nothing, because it contaminates harborage you will later want to bait.

Our treatment process

Every APC cockroach job runs the same sequence. The order is not arbitrary — each step exists because skipping it degrades the next one.

1. Inspection and species confirmation. We open appliance motor compartments, pull drawers, check hinge recesses and plumbing penetrations. We are mapping harborage, not counting insects. If it turns out to be Periplaneta in a drain stack rather than Blattella in a kitchen, the entire treatment changes.
2. Monitor placement. Sticky monitors go in at known and suspected harborage, giving a baseline count. Without a baseline, "it seems better" is the only available measure of success, and it is not a good one.
3. Sanitation and moisture findings. Written, and given to you. If there is a leak feeding the population, no chemistry will hold without correcting it.
4. Gel bait into harborage. Small placements, many of them, sited inside the cracks and voids the inspection identified — not along baseboards where it looks tidy.
5. Insect growth regulator. Applied where the population needs its reproduction broken rather than its adults reduced.
6. Targeted non-repellent residual, to travel routes and voids, never to food-contact surfaces and never over bait placements.
7. Follow-up visit. Monitors read against baseline, bait replenished where consumed, placements adjusted where it was not. This visit is included in the price and it is where we find out whether the population collapsed or relocated.

In a multi-unit building we will tell you plainly if treating your unit alone is unlikely to work, and what the adjoining-unit scope would need to be. That conversation costs us revenue in the short term and saves it in the long term.

The chemistry, and how it kills

You are entitled to know what is being applied in your home and how it works. All products used are registered with Health Canada's Pest Management Regulatory Agency, and we will give you the label and safety data sheet for anything applied.

Two design principles are worth understanding, because they explain why professional treatment looks different from what you would do yourself.

Delayed action is deliberate. A bait that killed on contact would kill the forager at the bait station and stop there. The actives above are chosen and dosed so the insect returns to harborage first. The population is then killed through droppings and carcasses reaching individuals that never fed. Fast knockdown is the enemy of thorough control.

Non-repellency is deliberate. Older pyrethroid sprays are detected and avoided. A non-repellent residual is walked through, which is the point.

Treatment timeline

Resistance and recent research

This is the part of the field that has changed most, and it is why a treatment protocol from 2005 underperforms today.

Cross-resistance across classes

A Purdue University field study led by Michael Scharf tested three resistance-management strategies in multi-unit buildings in Indiana and Illinois over six months, with cockroaches pre-tested to select the most effective actives for each site. Rotating three insecticide classes held populations flat but could not reduce them. A two-class mixture failed outright and populations grew. Only the single-insecticide treatment against a population with genuinely low starting resistance achieved near-elimination.²

The mechanism the study identified is the concerning part: cockroaches were developing cross-resistance to multiple classes simultaneously, meaning selection with one active conferred reduced susceptibility to others the population had never encountered. Scharf's own conclusion was that controlling these pests with chemicals alone is becoming close to impossible.²

Behavioural resistance: glucose aversion

The more elegant finding, and the one with the most direct effect on bait selection. Baits combine a non-deterrent active with a phagostimulant, historically glucose. In 2013, Wada-Katsumata, Silverman and Schal published work in Science showing that in glucose-averse populations, glucose stimulates not only the sugar-sensing gustatory receptor neurons but the bitter receptor neurons as well, while suppressing the sugar response. The cockroach has not learned to avoid the bait — it now genuinely tastes glucose as bitter.³

Subsequent work extended the problem. Cockroach saliva contains enzymes that rapidly convert complex sugars to glucose, so a glucose-averse insect rejects maltose and other oligosaccharides seconds after starting to feed, once salivary digestion has done its work.⁴ A 2023 study demonstrated that glucose- and disaccharide-containing baits also impede secondary mortality in these populations — the transfer chain breaks along with the primary feeding.¹⁴ The 2024 review by Wada-Katsumata and Schal summarises the current position, including the trait's contribution to olfactory learning-based bait avoidance and to assortative mating.⁵

Cultural history

Few insects carry as much symbolic freight, and most of it is unearned.

The nuclear survival myth. The claim that cockroaches would survive a nuclear war entered popular culture after Hiroshima and Nagasaki. It contains a kernel of truth — insects tolerate considerably higher radiation doses than mammals, largely because cells are most vulnerable during division and adult insects have fewer dividing cells. But cockroaches are not the most radiation-tolerant insect, and the "survives anything" framing is folklore rather than entomology.

Kafka, 1915. Gregor Samsa in Die Verwandlung is the source of half the cultural weight the animal carries. Kafka never names the species — the German is ungeheueres Ungeziefer, monstrous vermin — and he explicitly instructed his publisher that the creature must not be illustrated. The cockroach reading is an interpretation the text does not confirm.

Joe's Apartment (1996). MTV's musical comedy about a New York apartment with singing cockroaches is the high-water mark of cockroach cinema, which tells you something about the genre. WALL·E (2008) gave the species its only genuinely affectionate mainstream portrayal, in Hal, the protagonist's surviving companion.

"La Cucaracha." The Mexican folk song predates the Revolution and acquired its enduring verses during it, most famously attached to Pancho Villa's forces. It is a satirical marching song; the cockroach that cannot walk is generally read as political caricature.

The internet era. "Cockroaches will survive us all" persists as shorthand for indestructibility, and the Kafka reference remains a reliable literary shorthand for alienation. In pest control circles the running joke — with real diagnostic basis — is that seeing one cockroach means there are dozens you have not seen. Given a thigmotactic species with a short foraging radius, that one is essentially accurate.

References

Every claim above traces to one of these. Where we have described our own field practice rather than published research, it is stated as such in the text.

1. Tang, Q., Vargo, E.L., Ahmad, I., et al. (2024). Solving the 250-year-old mystery of the origin and global spread of the German cockroach, Blattella germanica. PNAS 121(22): e2401185121. doi.org/10.1073/pnas.2401185121
2. Fardisi, M., Gondhalekar, A.D., Ashbrook, A.R. & Scharf, M.E. (2019). Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach. Scientific Reports. pubmed.ncbi.nlm.nih.gov/31165746
3. Wada-Katsumata, A., Silverman, J. & Schal, C. (2013). Changes in taste neurons support the emergence of an adaptive behavior in cockroaches. Science 340(6135): 972–975. doi.org/10.1126/science.1234854
4. Wada-Katsumata, A. & Schal, C. (2021). Salivary digestion extends the range of sugar-aversions in the German cockroach. Insects 12(3): 263. doi.org/10.3390/insects12030263
5. Wada-Katsumata, A. & Schal, C. (2024). Glucose aversion: a behavioral resistance mechanism in the German cockroach. Current Opinion in Insect Science. doi.org/10.1016/j.cois.2024.101182
6. Rosenstreich, D.L., Eggleston, P., Kattan, M., et al. (1997). The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. New England Journal of Medicine 336: 1356–1362. nejm.org
7. Eggleston, P.A., et al. (1998). Relationship of indoor allergen exposure to skin test sensitivity in inner-city children with asthma. J Allergy Clin Immunol 102: 563–570. pubmed.ncbi.nlm.nih.gov/9802363
8. Gergen, P.J., et al. (1999). Results of the NCICAS environmental intervention to reduce cockroach allergen exposure in inner-city homes. J Allergy Clin Immunol. pubmed.ncbi.nlm.nih.gov/10069886
9. CBC News (21 November 2023). Rise in cockroach infestations in Winnipeg 'going to get worse', exterminators say. cbc.ca
10. First Nations Housing Knowledge Base — Cockroaches (citing Poulin Pest Control site inspection figures, 2022–2023). housing.fnhssm.com/cockroaches
11. CBC News. Cockroach problem bugs Manitoba Housing tenant. cbc.ca
12. CTV News Winnipeg (22 November 2024). 'It's a health hazard': cockroach infestation forces family out of Manitoba Housing apartment. ctvnews.ca
13. CBC News (15 April 2021). Once less common, Winnipeg seeing resurgence of cockroaches, pest control businesses say. cbc.ca
14. McPherson, S., Wada-Katsumata, A., Silverman, J. & Schal, C. (2023). Glucose- and disaccharide-containing baits impede secondary mortality in glucose-averse German cockroaches. J Econ Entomol 116(2): 546–553. pubmed.ncbi.nlm.nih.gov/36888567
15. Province of Manitoba — Cockroaches: Information for Manitobans. gov.mb.ca/cockroaches
16. Manitoba Housing — What You Need to Know: Cockroaches (PDF). gov.mb.ca/housing