# Two-spotted spider mite

> Tetranychus urticae, the commonest cannabis mite indoors: a 0.5 mm sap-feeder that stipples leaves pale and spins webbing, breeding fastest in hot, dry rooms.

- Canonical: https://genetixbay.com/knowledge/glossary/two-spotted-spider-mite.html
- Also written: spider mite, spider mites, twospotted spider mite, TSSM, red spider mite, Tetranychus urticae, mites
- 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"

The two-spotted spider mite (*Tetranychus urticae*) is a plant-feeding mite, not an insect, that pierces leaf cells and empties them. Each emptied cell shows as a pale dot, called [stippling](https://genetixbay.com/knowledge/glossary/stippling.md). Adults are about 0.5 mm long, pale yellow-green with two dark blotches on the body. Heavy populations spin silk that can cover [bud sites](https://genetixbay.com/knowledge/glossary/bud-site.md).

## In practice

Growers find them with a 10-20x hand lens on leaf undersides: mites, round clear eggs and cast skins. Speed is the problem. At about 24 °C (75 °F) a generation can finish in under a week, so a few stippled leaves become a webbed canopy within a month. Control rests on early scouting, cooler and more humid air where the stage allows, and [predatory mites](https://genetixbay.com/knowledge/glossary/predatory-mite.md) such as *[Phytoseiulus persimilis](https://genetixbay.com/knowledge/glossary/phytoseiulus-persimilis.md)* released while numbers are low. Contact sprays belong in veg, not on flowers. Check what is registered for cannabis locally before using any product.

## Don't confuse with

- **Broad mite and hemp russet mite**: far smaller, invisible without 40x or more, and they cause twisting or russeting rather than stippling.
- **Thrips damage**: silvery streaks with black specks of [frass](https://genetixbay.com/knowledge/glossary/frass.md), not fine dots.
- **Nutrient spotting**: no mites, eggs or webbing under the leaf.

## Related terms

[Broad mite](https://genetixbay.com/knowledge/glossary/broad-mite.md), [Phytoseiulus persimilis](https://genetixbay.com/knowledge/glossary/phytoseiulus-persimilis.md), [Neoseiulus californicus](https://genetixbay.com/knowledge/glossary/neoseiulus-californicus.md), [Scouting](https://genetixbay.com/knowledge/glossary/scouting.md), [Pesticide resistance](https://genetixbay.com/knowledge/glossary/pesticide-resistance.md)

## Read more

- [Spider mites on cannabis: life tables, ID and IPM](https://genetixbay.com/knowledge/pests/spider-mites.md)

## Sources

1. UC IPM. Pest Notes: Spider Mites (Publication 7405). University of California ANR. https://ipm.ucanr.edu/PMG/PESTNOTES/pn7405.html
2. Utah State University Extension. Two-Spotted Spider Mite (hemp). https://extension.usu.edu/planthealth/ipm/notes_ag/hemp-spider-mites.php
3. 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