Scale Insects on Rubber Plant — Identification and Treatment
Rubber Plant (Ficus elastica)
Symptoms
- brown oval or circular bumps on stems and leaf undersides
- bumps that don't brush off like dirt
- sticky, shiny residue on leaves and floor
- sooty black mold growing on sticky residue
- yellowing or browning leaves
- slow decline despite adequate care
Causes
Scale insect infestation
Rubber Plants are a preferred host for soft scale (Coccus hesperidum and related species) and brown soft scale. Scale insects settle onto stems and leaf undersides, insert a feeding tube into the plant's phloem, and draw sap while protected by their hard or waxy shell. They excrete honeydew — the sticky substance that coats surfaces and supports sooty mold growth. Heavy infestations cause yellowing, dropping leaves, and overall plant decline. Ficus elastica's waxy leaves and woody stems provide ideal habitat for scale. The insects blend particularly well with the brown, woody stems, making them easy to miss until populations are established.
How to Fix It
- 1
Confirm the diagnosis before you start scrubbing at bark-colored bumps: work a fingernail under one and check for an insect body. A bump that lifts away clean is scale; one that's fused into the woody stem tissue is a lenticel, not a pest.
- 2
For light infestations: wipe each scale off manually with a soft toothbrush or cloth soaked in 70% isopropyl alcohol. The alcohol kills the scale on contact and dissolves the protective coating.
- 3
Apply horticultural oil or neem oil spray to all stem and leaf surfaces, including undersides. The oil suffocates any scale missed during manual removal.
- 4
Once the scale is treated, give the glossy leaves a wipe-down with a damp cloth to clear off the sooty mold — the mold has nothing left to feed on once the honeydew source is gone, so it won't return.
- 5
Keep repeating the alcohol wipe and oil spray on roughly a two-week cycle for about six weeks running. Settled adults die fast under this routine; it's the crawlers hatching out between rounds on the woody stems that make the full six weeks necessary.
- 6
For severe infestations: consider a systemic insecticide (imidacloprid) applied as a soil drench — the plant absorbs it and it becomes toxic to scale feeding on plant sap.
Prevention
- Inspect stems and leaf undersides monthly
- Quarantine new plants before introducing to a collection
- Maintain good air circulation around the plant
Quick Summary
| Plant | Rubber Plant (Ficus elastica) |
|---|---|
| Category | Pests |
| Likely causes | Scale insect infestation |
| Fix steps | 6 steps — see above |