Scale insects
Small, hard brown bumps that don't brush off easily are scale insects, the other pest that occasionally finds this plant.
Diagnosis
Scale insects
What's happening
Scale are sap-sucking insects that hide under a waxy brown shell, looking like raised bumps stuck along the stems and leaf veins. They drain the plant's sap, which can slowly yellow leaves and leave a sticky residue called honeydew on the foliage below. Because the shell protects them, they're easy to miss until the colony is established.
How to fix it
Dab each bump with a cotton swab dipped in rubbing alcohol to break its protective shell and kill it, then wipe the plant down. For a wider infestation, spray the whole plant with insecticidal soap, covering stems and both leaf surfaces, and repeat every week for a few weeks to catch the crawlers that hatch later. Check nearby plants too, since scale spreads by walking to its neighbors.
What fixes it
- Insecticidal soap — Insecticidal soap clears scale crawlers across the whole plant — spray thoroughly and repeat weekly until the bumps are gone.
If that doesn't fix it
This is general guidance based on common symptoms; individual plants vary.
Read the full Cast Iron Plant care guide →
Reviewed June 2026 · how we check this