fungal infection on Calathea
Quick answer
If your Calathea has fungal infection, the most likely cause is: Fungal infections in Calathea (e.g., Cercospora leaf spot, Rhizoctonia root rot, Botrytis blight) proliferate in conditions of excess moisture, poor air circulation, and wet foliage. Overwatering creates anaerobic soil conditions favoring pathogenic fungi, while high humidity without airflow allows spore germination on leaf surfaces. Unlike bacterial spots (water-soaked appearance), fungal lesions are typically dry, brown, and may show concentric rings or fuzzy mycelium under humid conditions.
Start here:
- 1. Isolate infected plant immediately—fungi spread via spores
- 2. Remove all affected leaves with sterile shears, cutting well below visible lesions
Why Calathea gets fungal infection
Goeppertia spp.
Fungal infections in Calathea (e.g., Cercospora leaf spot, Rhizoctonia root rot, Botrytis blight) proliferate in conditions of excess moisture, poor air circulation, and wet foliage. Overwatering creates anaerobic soil conditions favoring pathogenic fungi, while high humidity without airflow allows spore germination on leaf surfaces. Unlike bacterial spots (water-soaked appearance), fungal lesions are typically dry, brown, and may show concentric rings or fuzzy mycelium under humid conditions.
How to reverse fungal infection on Calathea
- 1
Isolate infected plant immediately—fungi spread via spores
- 2
Remove all affected leaves with sterile shears, cutting well below visible lesions
- 3
Improve air circulation with small fan on low setting (not blowing directly on plant)
- 4
Apply copper-based fungicide or neem oil to remaining foliage every 7-10 days
- 5
Allow soil to dry more between waterings; never let pot sit in standing water
- 6
Repot in fresh sterile mix if root rot suspected; trim affected roots
- 7
Monitor humidity—maintain 60% but ensure air movement to prevent stagnant conditions
Keep fungal infection off this Calathea
Water only when top 2 inches soil dry; ensure excellent drainage and airflow; avoid wetting foliage; space plants for air circulation; remove dead leaves promptly; use sterile tools; apply preventive neem oil monthly during high-risk seasons.