The difference between residual and resolution
Two separate questions: how long does the product stay active, and how long does the pest problem stay solved? These are not the same. Product residual (how long the chemical remains effective) ranges from days (aerosol knock-down) to years (structural sealant materials, rodenticide bait matrix). The PMRA label specifies the registered residual period — this is what technicians use to set retreatment schedules. Pest problem resolution is driven by whether the root cause was addressed. A rodent treatment with excellent product residual but no structural sealing will require retreatment within weeks — the product kept working, but new rodents recolonised through the unsealed entries. A thorough structural exclusion with no chemical product can provide 5–10 years of rodent exclusion. The hierarchy: structural first, chemical second.
Residual periods by treatment type
| Treatment | Product residual | Problem resolution |
|---|---|---|
| Pyrethroid perimeter spray | 60–90 days | Perimeter prevention; doesn't address interior entry — combine with structural sealing for resolution |
| Indoor crack-and-crevice spray | 90–180 days | Protected from weather; residual depends on substrate and ventilation |
| Gel bait (ants, cockroaches) | 21–45 days per placement | Bait consumed by colony; refill when depleted; colony suppressed over 2–4 applications |
| Rodent bait stations | 60–90 days bait life | Population suppression only — structural exclusion provides resolution |
| Bed bug heat treatment | Permanent kill of exposed population | No chemical residual; re-treatment only if re-introduction occurs |
| Structural exclusion (hardware cloth, sealant) | 10–20 years | Physical barrier — hardware degrades over decades, not months |
| Wasp dust application | 30-day chemical residual | Nest killed in 24–48 hours; deterrence effect via residual in void |
| IGR (insect growth regulator) | 90–120 days | Disrupts reproduction; best combined with bait or spray for adults |
When to re-treat
- Quarterly subscription: every 90 days, preventive perimeter and inspection. The residual aligns with the visit schedule.
- Carpenter ant follow-up: 12 months post-treatment, with particular attention if the moisture source repair was extensive.
- Cockroach: typically a 3-visit protocol over 4–6 weeks, then monitoring. Re-treatment only if reintroduction occurs.
- Rodent: annual exclusion check post-treatment ensures sealing materials remain intact. No bait station retreatment needed if exclusion is solid.
- Bed bug: 14-day post-treatment monitoring check included. Re-treatment included in the initial price if any live bugs are found at the check.
- Wasps: nests are year-specific. Treating in year 1 does not prevent a new colony building in the same location in year 2 — but structural deterrence (void sealing, surface treatments) reduces re-establishment.
The maintenance subscription argument
For single-family homes in Metro Vancouver — especially homes with mature landscaping, older construction with aging weatherproofing, and proximity to green space — quarterly maintenance is structurally sound economically. The math: a single rodent infestation requiring professional treatment costs $395–$895. Carpenter ant treatment runs $295–$595 per active issue. A quarterly subscription at $139/visit ($556/year) provides four inspection-and-treatment visits and typically catches issues at activity day 1–7, when they are a DIY-level problem, rather than at day 30–90 when they become a professional-level job. The subscription doesn't just provide chemical coverage — it provides early-issue identification, annual structural exclusion checks, and documentation of pest pressure over time. For rental properties, this documentation has tenant communication value as well.