Brown-Spots-Bacterial on alocasia
What's Happening
Pseudomonas syringae and related bacteria infect Alocasia leaves through wounds or stomata, causing angular water-soaked lesions that darken to brown/black as tissue dies. Unlike fungal spots, bacterial lesions have straight edges bounded by leaf veins, creating geometric patterns. High humidity combined with poor air circulation promotes bacterial proliferation. The disease spreads via splashing water and contaminated tools.
How to Fix It
- 1
Remove severely infected leaves with sterilized scissors (wipe with 70% alcohol between cuts)
- 2
Apply copper-based bactericide weekly for 3-4 weeks following label instructions
- 3
Improve air circulation with small fan - avoid drafts directly on plant
- 4
Water at soil level only - never splash leaves; use room-temperature water
- 5
Avoid overhead watering or misting during treatment period
How to Prevent It
Use sterile potting mix; sterilize pruning tools before use; water at soil level only; maintain good air circulation; avoid working with wet plants; quarantine new plants; remove fallen debris promptly; maintain 60-80% humidity without leaf wetness.