Scale Insects: Identifying and Removing the 'Bumps' on Your Plants

Scale insects are one of the easiest indoor pests to miss because they often look like part of the plant—tiny brown or tan bumps on stems or along leaf veins. Late winter into early spring is when many people finally notice them, as plants weaken under low light and dry indoor air, allowing scale populations to build up quietly.

1. Typical Symptoms

• The “Bumps”: Hard or waxy bumps on stems, leaf undersides, or along the midribs of leaves.
• Yellowing Leaves: Affected leaves may turn yellow, look tired, or drop prematurely.
• Honeydew: A sticky residue on the leaves or nearby furniture/floors (common with “soft” scale).
• Sooty Mold: A black, dusty coating that grows on the sticky honeydew.

Common host plants: Ficus, Citrus, Hoya, Orchids, Succulents, and many woody houseplants.

2. Why This Peaks Now

• Winter Stress: Low light and dry air weaken a plant’s natural defenses.
• Slow Build-up: Scale insects reproduce gradually indoors, often reaching a “tipping point” by late winter.
• Spring Inspections: Many gardeners start inspecting their plants more closely as the days get longer, finally noticing the infestation.

3. Why Scale is Tricky

• Armor-Plated: Adults are often protected by a hard, waxy shell that makes many contact sprays ineffective.
• The “Crawler” Stage: The most vulnerable stage is the tiny, moving juvenile (crawler), which is almost invisible to the naked eye.
• Hiding Spots: They love to tuck into tight crevices: leaf nodes, branch junctions, and under the rims of pots.

4. Quick Checks (3 Minutes)

• The Scratch Test: Use a fingernail or a cotton swab to gently nudge a bump. If it comes off easily and leaves a slight mark behind, it’s an insect, not part of the plant.
• The Stickiness Test: Run your finger along the leaves or the rim of the pot. A sticky feeling suggests the presence of “honeydew” from sap-sucking pests.
• The Node Check: Look specifically where the leaf attaches to the stem—this is a favorite hiding spot for scale.

5. What To Do Now (Step-by-Step)

Step A: Isolate the Plant

Scale spreads slowly, but it will spread. Move the infested plant away from the rest of your collection immediately.

Step B: Manual Removal (Most Important)

Since adults are protected by shells, you must remove them physically.

• Dip a cotton swab in 70% isopropyl alcohol and dab individual scales to kill and remove them.
• For heavy infestations on woody stems, use a soft toothbrush to gently scrub the scales off.

Step C: Treat for Crawlers

Even after manual removal, tiny juveniles will remain.

• Apply horticultural oil or insecticidal soap to the entire plant, ensuring you hit every nook and cranny.
• The Schedule: Reapply every 7–10 days for 3–4 rounds to catch any newly hatched crawlers.

Step D: Clean Up

Wipe down the leaves and the area around the pot with warm, soapy water to remove sticky honeydew and prevent mold growth.

6. What Results to Expect

• 1–2 Weeks: Visible bumps should decrease after physical removal and initial treatment.
• 3–6 Weeks: Full control is usually achieved once all life stages have been addressed.
• Recovery: New growth should emerge clean. If the infestation was heavy, the plant may need extra light to regain its strength.

Recommendations

Do

• Prioritize manual removal first; sprays alone are rarely enough for scale.
• Check neighboring plants; scale often migrates slowly over months.
• Use alcohol-dipped swabs for a targeted, effective kill.

Don’t

• Don’t assume a bump is “just bark” without doing the scratch test.
• Don’t give up after one treatment—persistence is the only way to beat scale.
• Don’t fertilize an infested plant; it can encourage the soft growth that pests love.