What's eating my phalaenopsis-type dendrobium?

Phalaenopsis-type Dendrobium (Dendrobium bigibbum) is a tropical orchid vulnerable to mealybugs hiding in cane sheaths, scale on canes and leaves, and spider mites in dry indoor air. Its long flower spikes attract thrips. With its naturally erect, open habit, infestations are easier to spot than in dense-leaved orchids — inspect monthly.

White waxy tufts at cane nodes and sheaths; sticky deposits, sooty mold, and reduced new growth Apply 70% isopropyl alcohol with a cotton swab to all colonies; follow with weekly neem oil spray for a month

Brown or tan armoured bumps on canes and leaf undersides; yellowing and cane dieback over time Scrape off manually with an alcohol-soaked brush; spray with horticultural oil on a monthly basis

Pale speckling on leaves and fine webbing across cane nodes; more common in heated, low-humidity winter rooms Increase humidity; rinse plant in the shower; apply insecticidal soap thoroughly across all surfaces; repeat weekly

Silver streaking and brown scarring on the mauve-purple flowers; buds may drop before opening fully Remove affected spikes; spray with spinosad; keep plant away from open windows and infested outdoor plants during bloom