Grammatophyllum Leaf Spots: Virus, Mealybugs, or Fungus?

Grammatophyllum leave

Yellow/black spots on leaves (cut off). Cymbidiums showed similar before. Asks cause and prevention.

Three Likely Causes

Virus: Spotting/streaking; weakens plant long-term; new growth less robust. No cure. Insects (especially mealybugs) transmit. Test exists but doesn't catch all viruses.
Mealybugs: Visible in photo. Hide in crevices/sheaths. Sucking insects = excellent virus vectors. Reproduce fast.
Secondary fungal infection: Damaged tissue invites fungus. Treat with weekly copper-salt fungicide spray.

Isolate if virus suspected. Control mealybugs aggressively.

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