Scale Insects
Scale insects appear as small, immobile bumps on stems and leaves. They hide beneath a protective shell-like covering while feeding on plant sap.
Possible Causes
Introduction via New Plants
Why: Scale insects are commonly introduced on new or gift plants and are easily overlooked due to their disguise.
Signs to check: Small brown or tan bumps appeared after bringing in a new plant.
Stressed or Weakened Plants
Why: Plants under stress from poor light, overwatering, or nutrient issues are more susceptible to scale.
Signs to check: Infested plant was already struggling with other issues before scale appeared.
Lack of Natural Predators Indoors
Why: Without beneficial insects that control scale outdoors, indoor populations can grow quickly.
Signs to check: Scale numbers increase steadily over time without any natural decline.
What to Check
- 1Run a fingernail over suspected bumps — do they pop off? That is scale
- 2Check stems, leaf midribs, and leaf undersides for clusters
- 3Look for sticky honeydew on leaves and surfaces below the plant
- 4Check if black sooty mold is growing on the honeydew
What You Can Do
- Scrape off scale insects manually with a fingernail or old toothbrush
- Dab individual scale with rubbing alcohol on a cotton swab
- Apply horticultural oil to smother remaining insects
- Repeat treatment every 2 weeks for at least 6 weeks
- For severe infestations, consider a systemic insecticide as a last resort
When to Seek Help
- Scale covers large portions of stems and branches
- Plant is losing leaves and showing significant decline
- Sooty mold is coating the leaves, blocking light
Key Takeaway
Scale insects are tough to treat because their waxy shell protects them. Manual removal combined with oil or alcohol treatments over multiple applications is most effective.
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Sources: Missouri Botanical Garden, RHS. Content compiled from publicly available horticultural references for educational purposes. Source organizations are listed for transparency only and do not imply endorsement.