How do I treat scale insects on Calathea orbifolia?

Scrape visible adults off with a fingernail or soft toothbrush, then wipe the area with a cotton swab dipped in 70% isopropyl alcohol. Spray the whole plant with horticultural oil (1–2%) or insecticidal soap, repeat every 10–14 days for 3–4 cycles to catch crawlers. Systemic imidacloprid drenches (per label, not on edibles) work for stubborn infestations on woody indoor plants. Isolate the plant for 6–8 weeks after the last visible scale.

How do I prevent scale insects on Calathea orbifolia?

Inspect new plants closely along stems and the underside of older leaves. Wipe leaves and check stems monthly. Quarantine new plants for 3–4 weeks.

PEST DIAGNOSIS · CITED TO UC IPM — SCALES

Scale insects on Calathea orbifolia: how to identify and treat

How to identify scale insects on Calathea orbifolia

Small (1–5 mm), oval to round, brown or tan bumps on stems, petioles, and leaf undersides. They don’t move and can be scraped off with a fingernail. Sticky honeydew below the plant is often the first clue.

Damage signs to look for

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

Treatment ladder

Scrape visible adults off with a fingernail or soft toothbrush, then wipe the area with a cotton swab dipped in 70% isopropyl alcohol.
Spray the whole plant with horticultural oil (1–2%) or insecticidal soap, repeat every 10–14 days for 3–4 cycles to catch crawlers.
Systemic imidacloprid drenches (per label, not on edibles) work for stubborn infestations on woody indoor plants.
Isolate the plant for 6–8 weeks after the last visible scale.

Prevention going forward

Inspect new plants closely along stems and the underside of older leaves.
Wipe leaves and check stems monthly.
Quarantine new plants for 3–4 weeks.

Life cycle

Crawlers (mobile young) hatch from under adult scales and move to new feeding sites before molting into the immobile adult stage. Indoors there can be 2–3 overlapping generations a year.

Source

Identification, treatment intervals, and prevention guidance per UC IPM — Scales. Always follow the product label when applying any pesticide or horticultural oil.