# Thrips

> Slender insects about 1-2 mm long, chiefly western flower thrips (Frankliniella occidentalis), that rasp leaf surfaces, leaving silvery streaks dotted with black frass.

- Canonical: https://genetixbay.com/knowledge/glossary/thrips.html
- Also written: thrip, western flower thrips, WFT, Frankliniella occidentalis, onion thrips, Thrips tabaci
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Thrips are tiny, slender insects of the order Thysanoptera with fringed wings. On cannabis the main indoor species is western flower thrips (*Frankliniella occidentalis*); onion thrips (*Thrips tabaci*) also occur. They scrape the leaf surface and suck the leaking contents, leaving silvery or bronze patches speckled with black droppings. The word is both singular and plural.

## In practice

Thrips run a split life cycle. Eggs go inside the leaf, larvae feed on foliage, and most species drop to the growing medium to pupate. That is why good programmes hit two places: [predatory mites](https://genetixbay.com/knowledge/glossary/predatory-mite.md) such as *[Neoseiulus cucumeris](https://genetixbay.com/knowledge/glossary/neoseiulus-cucumeris.md)* or *[Amblyseius swirskii](https://genetixbay.com/knowledge/glossary/amblyseius-swirskii.md)* on the leaves, and soil predators such as *[Stratiolaelaps scimitus](https://genetixbay.com/knowledge/glossary/stratiolaelaps-scimitus.md)* or nematodes in the medium. Blue or [yellow sticky traps](https://genetixbay.com/knowledge/glossary/sticky-trap.md) at canopy height show trends; a jump from a few per card per week to dozens means act now. Western flower thrips resist many insecticide classes, so rotation by [mode of action](https://genetixbay.com/knowledge/glossary/mode-of-action.md) matters. Check what is registered for cannabis locally.

## Don't confuse with

- **Spider mite damage**: fine pale [stippling](https://genetixbay.com/knowledge/glossary/stippling.md), no streaks or black specks.
- **Leafminer trails**: winding tunnels inside the leaf, not surface scars.
- **Fungus gnats on traps**: dark flies with long legs, not slim straw-coloured insects.

## Related terms

[Neoseiulus cucumeris](https://genetixbay.com/knowledge/glossary/neoseiulus-cucumeris.md), [Amblyseius swirskii](https://genetixbay.com/knowledge/glossary/amblyseius-swirskii.md), [Orius](https://genetixbay.com/knowledge/glossary/orius.md), [Stratiolaelaps scimitus](https://genetixbay.com/knowledge/glossary/stratiolaelaps-scimitus.md), [Sticky trap](https://genetixbay.com/knowledge/glossary/sticky-trap.md)

## Read more

- [Thrips on cannabis: life table, temperature, scouting and biological control](https://genetixbay.com/knowledge/pests/thrips.md)

## Sources

1. UC IPM. Pest Notes: Thrips (Publication 7429). https://ipm.ucanr.edu/PMG/PESTNOTES/pn7429.html
2. UConn IPM. Biological Control of Western Flower Thrips. https://ipm.cahnr.uconn.edu/ipm-biological-control-of-western-flower-thrips/