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Scale Insects

Pest

Scale insects are small, sap sucking pests that hide under protective waxy shells on plant surfaces. They weaken plants by draining vital fluids and can lead to stunted growth or branch dieback if left to multiply.

Symptoms by part

Leaves

You will see yellowing spots, premature dropping, or a sticky residue called honeydew that often attracts black sooty mold.

Stems

Look for small, raised bumps that look like tiny shells or scabs. These bumps can be scraped off with a fingernail, revealing the soft insect underneath.

Causes

  • Introducing new, infested plants into your collection without checking them first.
  • Warm, dry indoor environments that lack natural predators.
  • Plants that are already stressed by poor light or incorrect watering.

Could be confused with

  • Mealybugs · Mealybugs look like tiny bits of white cotton, whereas scale insects have hard, smooth, or waxy shells.
  • Plant Galls · Galls are abnormal growths that are part of the plant tissue itself and cannot be scraped off like a scale insect.

Treatment

  1. Gently scrape the visible scale insects off the stems and leaves using a soft toothbrush or a cotton swab dipped in rubbing alcohol.
  2. Prune away heavily infested branches or leaves to reduce the total population.
  3. Apply fatty acids to the entire plant, ensuring you cover the undersides of leaves and all stem crevices, follow the label.

Without chemicals

  • Isolate the infested plant immediately to keep the pests from moving to neighbors.
  • Wipe down the plant surfaces with a damp cloth to remove honeydew and sooty mold.
  • Increase humidity around the plant to make the environment less favorable for the pests.

Chemical options

  • Fatty acids, spray directly onto the insects to soften their shells and cause dehydration, follow the label.

Preventing it

  • Inspect every new plant thoroughly for bumps on stems and leaves before bringing it home.
  • Keep your plants healthy with proper light and water so they can better resist pest attacks.
  • Wipe down leaves occasionally to keep them clean and make it harder for pests to settle.

Season

The warm growing season.

Spread risk

Moderate

Severity

Moderate

When to act

Act as soon as you spot the first bumps to prevent a full scale outbreak. If the plant is completely covered and failing to thrive despite treatment, it is best to discard it to protect your other plants.

Think it's Scale Insects?

This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Can I just wash the scale off?
Washing helps, but you must be thorough. Because they hide in tight crevices, you often need to follow up with a treatment to catch the ones you missed.
Why is my plant sticky?
That stickiness is honeydew, a sugary waste product excreted by the scale insects as they feed on your plant's sap.
Will my plant recover?
Yes, most plants recover well if you catch the infestation early and keep up with the cleaning and treatment steps.

Plants it affects

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This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.