# Scale insect

> Sap-sucking insects of the superfamily Coccoidea that settle on stems and leaves under a protective waxy or hard cover; rare on cannabis and usually introduced on other plants.

- Canonical: https://genetixbay.com/knowledge/glossary/scale-insect.html
- Also written: scale, scales, soft scale, armoured scale, armored scale, Coccoidea, brown soft scale
- 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"

Scale insects are sap feeders of the superfamily Coccoidea. After a short mobile [crawler](https://genetixbay.com/knowledge/glossary/crawler.md) stage, most settle in one spot and grow a cover: soft scales (family Coccidae, such as brown soft scale, *Coccus hesperidum*) produce a waxy dome and [honeydew](https://genetixbay.com/knowledge/glossary/honeydew.md), while armoured scales (Diaspididae) build a hard, detachable shield and do not make honeydew.

## In practice

Scale is unusual on cannabis because the crop cycle is short, but long-lived [mother plants](https://genetixbay.com/knowledge/glossary/mother-plant.md) kept beside houseplants can pick it up. Signs are small brown or grey bumps along stems and leaf veins that do not move, plus sticky honeydew and [sooty mould](https://genetixbay.com/knowledge/glossary/sooty-mould.md) for soft scales. Crawlers are the vulnerable stage; adults under their covers shrug off most contact sprays. [Horticultural oil](https://genetixbay.com/knowledge/glossary/horticultural-oil.md) in veg, physical removal and [parasitic wasps](https://genetixbay.com/knowledge/glossary/aphidius.md) are the usual tools. Badly infested mothers are often easier to replace from a clean cut. Check what is registered for cannabis locally.

## Don't confuse with

- **Mealybugs**: white and fluffy, still mobile as adults.
- **Aphids**: soft, mobile, breed fast.
- **Leaf spot lesions**: part of the leaf tissue; scales can be lifted off.

## Related terms

[Mealybug](https://genetixbay.com/knowledge/glossary/mealybug.md), [Aphid](https://genetixbay.com/knowledge/glossary/aphid.md), [Horticultural oil](https://genetixbay.com/knowledge/glossary/horticultural-oil.md), [Quarantine](https://genetixbay.com/knowledge/glossary/quarantine.md)

## Read more

- [Aphids on cannabis: species, life tables, population growth and IPM](https://genetixbay.com/knowledge/pests/aphids.md)

## Sources

1. Michigan State University Extension. Managing greenhouse insects. https://www.canr.msu.edu/news/managing_greenhouse_insects