Fungal Leaf Spot on anthurium
What's Happening
Fungal leaf spot diseases (Cercospora, Colletotrichum) on Anthurium appear as circular brown lesions with defined borders and sometimes yellow halos. These differ from physiological brown spots by their patterned appearance and tendency to spread between leaves. Infection occurs when water remains on leaf surfaces for 6+ hours in humid conditions with poor airflow, allowing fungal spores to germinate and penetrate leaf tissue. Nursery plants often carry latent infections that activate in home conditions.
How to Fix It
- 1
Diagnose accurately: Circular spots with defined borders and possible concentric rings = fungal; irregular blotches = physiological
- 2
Isolate immediately: Separate from other plants to prevent spore spread
- 3
Remove infected tissue: Cut spotted leaves at base with sterile scissors; discard in sealed bag
- 4
Fungicide application: Apply copper-based fungicide or neem oil covering all leaf surfaces; repeat every 7-10 days for 3-4 applications
- 5
Environmental fix: Increase airflow with fan and reduce humidity to 60-65% temporarily
- 6
Prevent recurrence: Resume treatment every 3-4 weeks as preventive during humid months
How to Prevent It
Avoid overhead watering that wets foliage; water at soil level only; maintain good air circulation with fans; space plants adequately to prevent leaf contact; quarantine new plants for 21 days; remove fallen debris from pot surface; keep humidity at 60-70% (not excessive 80%+).