Short answer
Prevent indoor pests in two layers: keep them out, then find the ones that get in while they are few. Quarantine every incoming plant for 2–3 weeks, scout weekly with a 10–20x lens and sticky cards, and set up predators in veg. Supported; the quarantine length is Grower practice.
Why
Most problems arrive on plants, people and media rather than appearing from nowhere: clones and mothers carry mites, thrips and mildew into rooms [1].
Early numbers are small and fixable. A spider mite generation can finish in under a week when it is warm, so a colony missed for a fortnight becomes a room problem [2].
Cards and lenses see different pests. Sticky cards catch flying adults such as gnats, thrips and whiteflies [3]; mites need a lens on leaf undersides [2].
Predators work best before the outbreak. Releasing when pests are first seen, at low numbers, is the standard advice [4].
Wet media breeds gnats. Constantly wet, organic-rich media and unfinished compost feed fungus gnat larvae [5].
The numbers
| Task | How often | Detail |
|---|---|---|
| Quarantine new plants | Every arrival | 2–3 weeks, separate space |
| Leaf-underside scouting | Weekly | 10–20x lens, about 12 leaves across the canopy |
| Sticky cards | Count and replace weekly | Yellow near media and canopy; blue for thrips |
| Preventive predators | In veg | Species that persist on low prey |
| Room clean-out | Between cycles | Plant-free and dry for several days |
What to do
- Start from seed or tested clean stock where you can.
- Quarantine and inspect every clone before it joins the room.
- Visit the grow before the garden, never after it in the same clothes. Keep pets and houseplants out.
- Screen or filter the intake.
- Let soil surfaces dry between waterings; store media bags closed.
- Scout and count weekly, and write it down.
- Release preventive predators in veg; avoid residual pesticides.
- Clean and empty the room between cycles.
Common mistakes
- Skipping quarantine "because it's from a friend".
- Waiting for webbing before looking.
- Hanging sticky cards and never counting them.
- Spraying on a calendar instead of scouting.
Related
- Full article: Sanitation and disease prevention for cannabis grows
- Guide: Pest prevention for beginners
- Answers: How pests get into a sealed tent · Do sticky traps work?
- Terms: IPM · quarantine · predatory mite
