Dendrobium Leaf Spots and Yellowing: Sucking Insect Infestation

Diagnosis: Scale, Mealybugs, Aphids, or Thrips

Large, old Dendrobium in oak tree for years. Clear dots on leaves along spike → leaves yellowing. Flower spikes ready to open.

Insect Evidence

• Clear dots = feeding sites from sucking insects.
• Most likely: boisduval scale, mealybugs, aphids, thrips.
• Yellowing leaves = nutrient loss from feeding.

Treatment Plan

1. Inspect thoroughly—check leaf undersides, stems, pseudobulbs.
2. Spray systemic insecticide (Merit or Bayer Advanced Garden).
3. Avoid spraying buds/spikes directly.
4. Systemics need days to absorb—treat now.

Prognosis

• Yellow leaves will drop—plant survives.
• Flowers should open unless buds attacked.
• Monitor for reinfestation; retreat in 3 weeks for hatchlings.

Tree-growing Dendrobiums are prone to insect migration—regular inspection essential.