Why 'I don't see any cockroaches' isn't enough
Cockroach infestations are not self-announcing as they rebuild. German cockroaches are nocturnal, spend 75–90% of their lives in harborages, and do not produce visible activity at low population densities. A population that has been reduced to a founding group of 20–30 individuals (surviving in deep wall voids or arriving as recent migrants from adjacent units) will be invisible to casual observation. It will, however, be detectable on sticky monitors placed at harborage sites for 48-hour periods. The difference between confirmed elimination and visible absence is approximately 4–8 weeks — the time from a 20-individual founding population to a visible moderate infestation. Structured post-treatment monitoring with sticky traps catches this reinfestation window at the 20-individual stage, when a single additional treatment visit resolves it completely, rather than at the 200-individual stage, which requires another full treatment cycle.
The three-phase post-treatment monitoring protocol
Phase 1 (weeks 8–10): final treatment confirmation. Deploy sticky monitors at all primary harborage sites (refrigerator motor, stove back wall, dishwasher, under-sink plumbing, two or three additional sites). Leave for 48–72 hours. Zero captures = initial confirmation of treatment success. One to two captures = small residual population, one additional treatment visit required. Three or more captures = treatment has not fully eliminated the population, full protocol extension needed.
Phase 2 (weeks 10–16): 90-day monitoring period. Monthly sticky monitor deployment at three to five high-priority locations. This frequency detects migration reinfestation at the early stage. In multi-unit buildings, Phase 2 monitoring should include at least one trap in each adjacent unit (above, below, left, right of the treated unit) with building management's agreement. Zero captures across all monthly check points = confirmed sustained elimination.
Phase 3 (months 4–12): quarterly monitoring. One set of traps placed at the three most sensitive historical harborage sites, left for 48 hours, checked and replaced quarterly. This is the prevention monitoring that catches any new introduction (from new building residents, deliveries, or adjacent unit migration) before it establishes.
| Phase | Timing | Frequency | Trap Locations | Action Threshold |
|---|---|---|---|---|
| 1 — Treatment confirmation | Week 8–10 | One 48-72h deployment | All primary harborage sites | 0 = confirmed; 1–2 = one additional visit; 3+ = protocol extension |
| 2 — 90-day monitoring | Weeks 10–22 | Monthly | 3–5 priority sites + adjacent unit monitors | Any capture = investigation + targeted treatment |
| 3 — Quarterly prevention | Months 4–12 | Quarterly | 3 historical hotspot sites | Any capture = full assessment and targeted treatment |
Reinfestation timelines in Metro Vancouver
Metro Vancouver's high-density housing creates reinfestation risk that is qualitatively different from detached-home scenarios. In a detached home, reinfestation from an adjacent building requires physical transport of cockroaches (usually via goods or moved appliances). In a high-rise tower, adjacent unit populations are one unsealed outlet box or one open service-chase gap away from entering a successfully treated unit. The typical reinfestation timeline from a successfully treated Metro Vancouver apartment unit: 30–90 days if adjacent units have active infestations and building-wide coordination has not been achieved. This is why the post-treatment monitoring protocol in multi-unit buildings must include adjacent unit monitoring, and why successful multi-unit cockroach management requires the strata-level coordination described in [cockroach strata escalation](/guide/cockroach-strata-escalation).