Scale insect
Immobile brown or straw-coloured bumps along stems and leaf veins, which look far more like part of the plant than like an animal. That is why they are usually noticed indirectly — through sticky honeydew and sooty mould — long after the population has established.
Caused by: Coccoidea · also called scale, brown scale
What brings it on
Warm, sheltered positions: indoors, in conservatories and on wall-trained plants outside. Populations build slowly and are often well advanced before anyone looks closely.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Scale insects
Checked 2026-08-13
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Check stems and the undersides of leaves on new plants, running a finger along the veins. A scale that can be scraped off with a fingernail is a scale, not a blemish.
source
Sourced guidancemoderate confidence
- Royal Horticultural Society: Scale insects — prevention
Checked 2026-08-13
Dealing with it once it is there
- Scrape or wipe them off by hand. The adults under the shells are protected from most contact treatments, which is why physical removal remains the most reliable approach on a plant small enough to handle.
source
Sourced guidancemoderate confidence
- Royal Horticultural Society: Scale insects — control
Checked 2026-08-13
Signs that lead here
Each of these lists the other things that produce the same sign, and how to tell them apart.
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.