White Spots on Dendrobium Leaves: Boisduval Scale or Mealybugs

White Dots on Dendrobium Leaves—Insect Diagnosis

Small white dots on both sides of older Dendrobium leaves, not on new growth. Could be boisduval scale or mealybugs.

Alcohol Test

1. Dip soft cloth in isopropyl alcohol.
2. Wipe spots.
3. If they come off: Scale or mealybugs.
4. If they remain: Could be thrips, spider mites, or fungal spots (look for holes/pitting).

Treatment for Scale/Mealybugs

• Wipe all visible insects off with alcohol (weekly × 3–4 weeks).
• Or use systemic orchid insecticide per label (3 applications, 3 weeks).
• Check leaf undersides, leaf axils, roots—hideouts.

If Chewing Insects (Thrips/Mites)

• Spots are feeding damage—won't disappear until new leaves grow.
• Use appropriate miticide/insecticide.

Old leaves with damage will eventually shed. Protect new growth.