What's eating my dendrobium phalaenopsis?

Dendrobium phalaenopsis orchids grown indoors are most threatened by spider mites in warm dry conditions and mealybugs at pseudobulb bases and leaf axils. Scale insects attach to canes and leaves. Fungus gnats trouble bark-based mixes if kept too wet. Good air circulation and appropriate watering prevent most outbreaks.

Fine silvery stippling across leaf surfaces; webbing on undersides in heavy infestations, causing leaf drop. Increase humidity; wipe leaves with damp cloth; apply neem oil or specialist miticide, repeating every 5–7 days.

White cottony deposits in leaf axils, at base of pseudobulbs, and in bark mix; leaves yellow and weaken. Apply 70% isopropyl alcohol with a cotton swab; drench bark mix with neem oil solution and repeat fortnightly.

Hard brown or soft waxy bumps on canes and leaf undersides; honeydew leads to sooty mold. Scrape off with a soft brush; treat with horticultural oil spray or systemic insecticide labelled for orchids.

Larvae damage fine roots in bark mix kept too moist; adults swarm around the pot. Allow bark to dry between waterings; use Bti drench (mosquito dunks in water) and sticky yellow traps.