The six signs ranked by reliability and timing
Cockroach infestations follow a predictable visibility curve. In the early stage (first 4–8 weeks in a unit), the colony is small and largely hidden. The signs visible at this stage — droppings and shed casings — are subtle and easily missed. By the time live cockroaches are visible in daylight, populations have typically exceeded harborage capacity, indicating a moderate to heavy infestation that has been present for months. Catching the early signs is the difference between a fast two-visit treatment and a full 8-week multi-unit protocol.
- Droppings: small black or very dark brown specks 1–2 mm in diameter — the texture and appearance of coarse-ground pepper or coffee grounds. Found in cabinet corners, behind appliances, under the stove, in drawer corners. High concentration of droppings at one location indicates a primary harborage nearby.
- Shed casings: pale translucent shells from molting nymphs. Each nymph sheds six times before becoming an adult; each shed leaves behind a complete exoskeleton. Found near harborages, these confirm resident nymphs — meaning active reproduction, not just adult migration.
- Oothecae (egg cases): dark brown 7 mm capsule-shaped cases deposited in protected crevices. Finding even one ootheca in a cabinet crack or behind an appliance confirms a reproducing female was present recently.
- Musty or sweet odour: heavy infestations produce a distinctive smell from accumulated cockroach pheromones, feces, and dead individuals. This is a late-stage sign — if you can smell a cockroach infestation, the population is large. The odour source is typically a concentrated harborage, often inside a void or cabinet base.
- Smear marks: dark irregular streaks or dots on warm surfaces where cockroaches walk through accumulated droppings. Common on the top of the refrigerator, behind the microwave, on the inside walls of lower cabinets near plumbing. Smear marks indicate frequent cockroach traffic through that path.
- Live sightings: usually a late-stage indicator in German cockroach infestations, which are highly nocturnal. A daytime sighting almost certainly indicates population pressure has exceeded harborage capacity — meaning a larger infestation than the sighting alone suggests. Sightings at night under a kitchen light are more typical and do not carry the same severity implication.
Where to look — the high-probability locations
- Under the refrigerator — motor heat makes this a top harborage. Pull out the lower kickplate and inspect with a flashlight.
- Behind and under the stove — grease, heat, and proximity to food make this the single most reliable harborage location in residential kitchens.
- Under and behind the dishwasher — motor and heating element heat combined with water access.
- Inside lower cabinet bases near plumbing penetrations — gaps around pipes under the sink are primary entry and harborage sites.
- Inside drawer corners at the back — droppings accumulate here because cockroaches run along the back edges of drawers.
- Inside the electrical outlet boxes on shared walls — particularly in multi-unit buildings.
- Bathroom vanity cabinets near plumbing — cockroaches need water and these locations provide it.
- Inside the motor housing of small appliances left on countertops (toasters, coffee makers) — warm and protected.
Using sticky monitors to confirm or rule out
Sticky monitor traps are the professional tool for confirming active infestation, estimating population level, and tracking treatment progress. They are also available at hardware stores and are the best self-help diagnostic for Metro Vancouver residents who've found evidence but aren't sure about severity. Place traps flat on surfaces along baseboards and against walls — not in the open. Best placements: under the refrigerator on the floor against the motor housing wall, inside the lower cabinet under the sink against the back wall, against the back wall behind the stove. Leave traps undisturbed for 48–72 hours before inspecting. Zero captures with evidence present may mean population is in deeper voids rather than actively foraging. Multiple captures across multiple trap locations confirms active, distributed infestation requiring professional attention.
What to do if you find evidence
Single sign at one location (e.g., a few droppings under the sink, no other evidence): deploy bait stations and sticky monitors, monitor for two weeks. Two or more types of signs across two or more locations: this is an active infestation. In a detached home, self-treatment with gel bait is reasonable for a small population. In any multi-unit building, escalate to landlord or strata immediately — single-unit self-treatment in multi-unit buildings almost never produces lasting results because of migration pressure from adjacent units. See [cockroaches in your Metro Vancouver apartment: the strata-aware playbook](/guide/cockroaches-in-apartment) for the escalation protocol.