White Grainy Spots on Orchid Leaves = Boisduval Scale: Australian Grower Alert

Diagnosis: Boisduval Scale

White, grainy, removable dots sucking leaf sap = Boisduval scale—one of the worst scale insects for orchids. They kill slowly but surely.

Treatment Protocol (Australia)

1. Source systemic insecticide for scale on orchids (e.g., imidacloprid, acephate—check local nursery).
2. Apply per label—systemics move up through roots to leaves; scale die when feeding.
3. Minimum 3 applications, 7–10 days apart (kills hatchlings).
4. Scrub visible scale with alcohol Q-tip pre-treatment.

Watering Check

3×/week may be too much for most orchids. Water when mix barely moist. Unknown ID makes precise advice hard—most orchids prefer drying between waterings.

Urgency

Boisduval spreads fast. Treat immediately and isolate. Your plant can recover if caught now.