Sago Palm Brown Bumps Under Leaves: Scale Insects, Not Fungus

Diagnosis

Brown bumps on leaf undersides + yellow lower fronds = scale insects (likely Cycad aulacaspis scale). Bumps = adult females; yellowing = sap loss.

Indoor Treatment

1. Isolate plant: Prevent spread.
2. Scrape scales: Fingernail/soft brush. Pale green spot underneath = live feeding site.
3. Insecticidal soap or neem oil: Spray all surfaces weekly × 3.
4. Horticultural oil (if plant can go outside): Better coverage, suffocates all stages.

AC Unit Factor

Constant A/C = very low humidity → favors spider mites, not scale. But scale tolerates it. Fluorescent light = insufficient for sago (needs bright light).

Outlook

Same lethal cycad scale disease as outdoors. Indoor may slow it. Monitor new growth—if clean, treatment working.

Early, aggressive physical removal + oil/soap is best indoor shot. Consider replacing with Zamia or Dioon if it fails.