How do I get rid of scale insects on houseplants?

Scrape visible adults off with a fingernail or soft toothbrush, then wipe the area with a cotton swab dipped in 70% isopropyl alcohol (per UW–Madison Extension). Spray the whole plant with horticultural oil or insecticidal soap, following the label. UW–Madison Extension notes it usually takes at least three treatments, repeated every six to seven days until the scales are gone. Systemic imidacloprid (per label, not on edibles) can help against soft scales, but UC IPM notes it does not control most armored scales. Keep the plant isolated from your other plants until no scale remains.

How do I prevent scale insects?

Inspect new plants closely along stems and the underside of older leaves. Wipe leaves and check stems regularly. Watch new plants closely: UC IPM advises checking them weekly, then monthly once several weeks pass with no problems.

Pest identification · Coccoidea

Scale Insects on Houseplants

Scale insects are armored or soft-bodied sucking pests that attach to stems and leaves and feed on plant sap. Adults look like small brown or tan bumps and don’t move once settled. Heavy infestations weaken the plant and produce honeydew that attracts sooty mold.

Read the full scale insects treatment guide

How to identify scale insects

Small oval to round brown or tan bumps on stems, petioles, and leaf undersides; UC IPM gives their coverings as 1/25 to 1/4 inch long. They don’t move and can be scraped off with a fingernail. Sticky honeydew below the plant is often the first clue.

Damage to look for

Yellowing leaves, leaf drop, slowed growth, sticky honeydew, sooty mold on lower leaves.

Life cycle (why they spread so fast)

Crawlers (mobile young) hatch from under adult scales and move to new feeding sites before molting into the immobile adult stage. Most armored scales have several generations a year; most soft scales have one.

How to get rid of scale insects

1Scrape visible adults off with a fingernail or soft toothbrush, then wipe the area with a cotton swab dipped in 70% isopropyl alcohol (per UW–Madison Extension).
2Spray the whole plant with horticultural oil or insecticidal soap, following the label. UW–Madison Extension notes it usually takes at least three treatments, repeated every six to seven days until the scales are gone.
3Systemic imidacloprid (per label, not on edibles) can help against soft scales, but UC IPM notes it does not control most armored scales.
4Keep the plant isolated from your other plants until no scale remains.

How to prevent scale insects

Inspect new plants closely along stems and the underside of older leaves.
Wipe leaves and check stems regularly.
Watch new plants closely: UC IPM advises checking them weekly, then monthly once several weeks pass with no problems.

Per-species treatment guides

Treatment varies slightly by plant. Find your species below for a dedicated guide.

Source: UC IPM — Scales. Other figures: UW–Madison Extension — Scale Insects and UC IPM — Houseplant Problems, as named in the text.