Scale insects on houseplants: how to spot them and what to do
Scale insects are sap-feeding pests that look like small bumps on stems and the undersides of leaves, so they often go unnoticed until the leaves turn sticky or yellow. Move the plant away from the others, scrape off the scale and wipe the leaves, and repeat every few days, since the crawling young keep hatching.
What does it look like?
- Small round or oval bumps, brown, grey or white, stuck to stems and the undersides of leaves, that scrape off with a fingernail.
- Sticky, shiny leaves and a black, sooty coating on them or on the surface below the plant: honeydew from soft scale.
- Yellow spots or whole yellowing leaves, slow growth and leaf drop on a plant that is otherwise watered well.
- White, cottony egg masses under some species, easy to confuse with mealybugs.
Why does it happen?
- A new plant that came with scale, kept close to others before it was checked.
- Crawlers walking or being carried from one plant to the next, or on hands and tools.
- Warm, dry indoor air with no natural enemies, where a few scale become many.
- A plant already weakened by low light or poor watering, which scale take advantage of.
What can you do about it?
- Move the plant away from others and check its neighbours, especially stems and leaf undersides.
- Scrape or pick the scale off with a fingernail, a soft toothbrush or a cotton bud dipped in rubbing alcohol, and wipe the leaves clean of honeydew and sooty mould with a damp cloth.
- Repeat every few days for a few weeks: the shells protect the adults, and new crawlers keep hatching.
- For a heavy infestation, spray an insecticidal soap or a horticultural oil at the label rate, covering stems and the undersides of leaves, when the crawlers are active.
- Prune away stems that are encrusted with scale, and bin the cuttings.
When you photograph a plant with this problem, Leafsight gives an assessment that names the likely problem, how serious it looks and how sure it is. Your first assessment that finds a problem includes care steps like these; with Pro or a one-time unlock, every one does.
When should you look closer?
- Fluffy white masses that move when prodded: mealybugs rather than scale, treated much the same way.
- Bumps that do not scrape off and are part of the leaf: normal features of the plant, such as the raised dots on some ficus.
- Sticky leaves with tiny green or black insects rather than bumps: aphids.
Questions
What do scale insects look like on houseplants?
Scale insects look like small bumps rather than insects: round or oval shells, brown, grey or white, a few millimetres across, stuck to stems and the undersides of leaves. They do not move. Soft scale leave sticky honeydew that turns black with sooty mould; armoured scale do not. If a bump scrapes off with a fingernail and leaves a mark, it was scale.
How do I get rid of scale insects on indoor plants?
Isolate the plant, then remove the scale by hand: scrape them off with a fingernail or soft toothbrush, or dab each with a cotton bud dipped in rubbing alcohol, and wipe the leaves clean. Repeat every few days for several weeks, because new crawlers keep hatching. For a heavy infestation, spray insecticidal soap or horticultural oil at the label rate, covering the leaf undersides.
Why are my plant leaves sticky?
Sticky leaves on a houseplant usually mean a sap-feeding pest is excreting honeydew: soft scale, mealybugs, aphids or whitefly. Look at the stems and the undersides of leaves for small brown bumps (scale), white fluff (mealybugs) or tiny green insects (aphids). A black, sooty film on the sticky leaves is mould growing on the honeydew; it wipes off once the pest is dealt with.
Does scale spread to other plants?
Yes. Adult scale insects stay put, but their young, called crawlers, walk to new leaves and can be carried to other plants on hands, tools, pets or a breeze. Keep an affected plant apart from the others until no new scale has appeared for a few weeks, and check nearby plants closely, especially along stems and under leaves.
When should I give up on a plant with scale?
When scale still covers most of the stems after several weeks of scraping and wiping, and the plant keeps losing leaves, it may not be worth saving, especially if it sits close to other plants. Clean, healthy stem tips can sometimes be rooted as cuttings first; check them closely and keep them apart. A larger or treasured plant is usually worth a few more rounds.
Not sure? Check with a photo
Leafsight looks at a photo of the leaf, asks a few questions about light, watering and drainage, and gives an assessment of the likely problem with care steps. A photo assessment can be wrong: for a hands-on look, ask a local garden centre or plant clinic.
Related problems
- Mealybugs: white fluffy spots on plants and what to do
- Aphids on plants: how to spot them and what to do
- Yellow leaves on houseplants: common causes and what to check
- Spider mites on plants: how to spot them and what to do
Sources
Updated 2026-11-04. All plant problems.
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