Scale Insects: How to Identify and Manage Them

How to identify scale insects

Scales resemble raised bumps or scabs that do not brush off easily. Soft scale infestations show honeydew and sooty mold; armored scales have a separate cover you can flick off to reveal the insect beneath.

• Small circular or oval bumps on stems and leaf undersides
• Soft scale: sticky honeydew and black sooty mold present
• Armored scale: dry, shell-like cover, no honeydew

Least-toxic management, in order

1. 1Prune and remove — Cut out and destroy heavily infested twigs and rub scales off small indoor plants.
2. 2Target crawlers with oil — Apply horticultural oil to coat all bark and leaf surfaces when the mobile crawler stage is active.
3. 3Dormant oil on woody plants — A winter dormant-oil application can kill scales overwintering on trunks and branches.
4. 4Conserve natural enemies — Parasitic wasps and predators often keep scale in check; avoid broad-spectrum sprays that kill them.

When to escalate

Heavy, recurring scale on trees and shrubs may need professionally timed treatment. Because control depends on correctly separating soft from armored scale, send a sample to your regional Extension diagnostic lab if you are unsure before escalating beyond oil.

⚠ Some systemic insecticides do not control armored scales even though they affect soft scales. Confirm which scale you have before choosing any product.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• University of Maryland Extension — Introduction to Scale Insects — Difference between soft and armored scales, honeydew, and identification cues
• Clemson Home & Garden Information Center — Armored Scale Insects — Targeting the crawler stage with horticultural oil, dormant oil, and that systemic imidacloprid does not kill armored scales

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