How do I treat thrips on Philodendron?

Rinse the plant thoroughly to dislodge adults, then spray with insecticidal soap or spinosad-based spray every 5–7 days for 3–4 cycles. Drench the soil with a systemic insecticide (imidacloprid, per label, not on edibles) since pupae hide in the medium. Yellow or blue sticky cards trap winged adults and help monitor population. Isolate the plant for at least 4 weeks.

How do I prevent thrips on Philodendron?

Inspect new plants (especially flowering ones, where thrips often hide) for 3–4 weeks before adding to a collection. Avoid bringing in cut flowers from outdoors during thrips season.

PEST DIAGNOSIS · CITED TO UC IPM — THRIPS

Thrips on Philodendron: how to identify and treat

How to identify thrips on Philodendron

Adults are slender, 1–2 mm long, pale yellow to dark brown. Easier to spot than the thrips: silvery streaks on leaves, distorted new growth, and tiny black dots (frass) on leaves.

Damage signs to look for

Silvery or bronze streaks on upper leaf surfaces, distorted or curled new growth, tiny black specks of frass, leaf drop in severe cases.

Treatment ladder

Rinse the plant thoroughly to dislodge adults, then spray with insecticidal soap or spinosad-based spray every 5–7 days for 3–4 cycles.
Drench the soil with a systemic insecticide (imidacloprid, per label, not on edibles) since pupae hide in the medium.
Yellow or blue sticky cards trap winged adults and help monitor population.
Isolate the plant for at least 4 weeks.

Prevention going forward

Inspect new plants (especially flowering ones, where thrips often hide) for 3–4 weeks before adding to a collection.
Avoid bringing in cut flowers from outdoors during thrips season.

Life cycle

Egg to adult in ~15 days at room temperature. Eggs are laid inside leaf tissue (hard to remove). Pupation happens in soil, which makes integrated soil + foliar treatment important.

Source

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