# How do I prevent pests in an indoor grow?

> To prevent pests in an indoor grow, stop them coming in and catch the rest early. Quarantine every new clone for 2–3 weeks, start from seed where you can, keep outdoor clothes, pets and houseplants out, and work clean rooms first. Scout leaf undersides weekly with a 10–20x lens, count sticky cards weekly, release preventive predators in veg, and clean the room between cycles.

- Canonical: https://genetixbay.com/knowledge/answers/how-to-prevent-pests-indoors.html
- Topic: Pests · Type: How-to
- Evidence: Supported · Status: Draft: awaiting expert review
- Full article: [Sanitation and disease prevention for cannabis grows](https://genetixbay.com/knowledge/diseases/sanitation-and-prevention.md)
- Also asked as: IPM for an indoor grow | How do I prevent pests in a grow tent? | How do I keep bugs out of my grow room? | Pest prevention routine indoors | How do I stop spider mites and thrips getting in?
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## 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](https://genetixbay.com/knowledge/glossary/sticky-trap.md), 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](https://genetixbay.com/knowledge/glossary/mother-plant.md) carry [mites](https://genetixbay.com/knowledge/glossary/two-spotted-spider-mite.md), [thrips](https://genetixbay.com/knowledge/glossary/thrips.md) 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](https://genetixbay.com/knowledge/glossary/whitefly.md) [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](https://genetixbay.com/knowledge/glossary/fungus-gnat.md) 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

1. Start from seed or tested clean stock where you can.
2. Quarantine and inspect every clone before it joins the room.
3. Visit the grow before the garden, never after it in the same clothes. Keep pets and houseplants out.
4. Screen or filter the intake.
5. Let soil surfaces dry between waterings; store media bags closed.
6. Scout and count weekly, and write it down.
7. Release preventive predators in veg; avoid residual pesticides.
8. 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](https://genetixbay.com/knowledge/diseases/sanitation-and-prevention.md)
- Guide: [Pest prevention for beginners](https://genetixbay.com/knowledge/guides/pest-prevention-for-beginners.md)
- Answers: [How pests get into a sealed tent](https://genetixbay.com/knowledge/answers/how-did-pests-get-in-my-tent.md) · [Do sticky traps work?](https://genetixbay.com/knowledge/answers/do-sticky-traps-work.md)
- Terms: [IPM](https://genetixbay.com/knowledge/glossary/ipm.md) · [quarantine](https://genetixbay.com/knowledge/glossary/quarantine.md) · [predatory mite](https://genetixbay.com/knowledge/glossary/predatory-mite.md)

## Follow-up questions

**How long should I quarantine new clones?** Quarantine new cannabis clones in a separate space for at least 2–3 weeks, which grower practice treats as long enough for a pest generation and latent powdery mildew to show. Inspect leaf undersides with a 30–60x loupe for mites, thrips, whitefly eggs and mildew. Test mothers for hop latent viroid too, because no inspection will show a viroid.

**Should I release predatory mites before I see pests?** Yes, preventive predator releases suit indoor cannabis, as long as you choose species that survive on few prey. Neoseiulus californicus tolerates warmer, drier rooms and persists at low prey numbers, so it fits preventive use against spider mites, and soil predatory mites help against gnats and thrips pupae. Release in veg and avoid residual pesticides, which kill them.

**What should I check every week for pests?** Every week, check the undersides of about a dozen leaves across the canopy with a 10–20x lens, tap a few branches over white paper, and count and replace sticky cards. Note hot spots near lights and walls, and write the counts down. Rising card counts or the first stippled leaves are your early warning, while numbers are still small enough to fix in veg.

## Sources

1. Punja ZK et al., 2019. Pathogens and molds affecting production and quality of Cannabis sativa L. Frontiers in Plant Science 10:1120. https://www.frontiersin.org/articles/10.3389/fpls.2019.01120/full
2. UC IPM. Pest Notes: Spider Mites (Publication 7405). University of California ANR. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7405.html
3. Michigan State University Extension. Managing greenhouse insects. https://www.canr.msu.edu/news/managing_greenhouse_insects
4. UConn IPM. Biological control of spider mites (2019 fact sheet). https://ipm.cahnr.uconn.edu/wp-content/uploads/sites/3216/2022/12/2019biologicalcontrolofspidermitesfinal2-1.pdf
5. UC IPM. Pest Notes: Fungus Gnats (Publication 7448). https://ipm.ucanr.edu/legacy_assets/pdf/pestnotes/pnfungusgnats.pdf