fungal infection leaf spot on Begonia
Quick answer
If your Begonia has fungal infection leaf spot, the most likely cause is: Leaf spot diseases in begonias—whether bacterial (Xanthomonas campestris) or fungal (Cercospora, Alternaria)—manifest as circular to irregular brown/black lesions with defined margins. Bacterial spots often show yellow halos; fungal spots may display concentric rings or fuzzy growth in center. Both pathogens enter through wounds, hydathodes (water pores), or stomata when foliage remains wet 6+ hours from overhead watering, condensation, or high humidity with poor airflow.
Start here:
- 1. Triage assessment: Inspect all leaves; remove any with >30% coverage or spreading lesions; keep leaves with isolated spots for monitoring
- 2. Sterile removal: Cut affected leaves with sterile scissors 1 inch below visible lesion; seal in plastic bag for trash disposal
Why Begonia gets fungal infection leaf spot
Begonia spp.
Leaf spot diseases in begonias—whether bacterial (Xanthomonas campestris) or fungal (Cercospora, Alternaria)—manifest as circular to irregular brown/black lesions with defined margins. Bacterial spots often show yellow halos; fungal spots may display concentric rings or fuzzy growth in center. Both pathogens enter through wounds, hydathodes (water pores), or stomata when foliage remains wet 6+ hours from overhead watering, condensation, or high humidity with poor airflow.
How to reverse fungal infection leaf spot on Begonia
- 1
Triage assessment: Inspect all leaves; remove any with >30% coverage or spreading lesions; keep leaves with isolated spots for monitoring
- 2
Sterile removal: Cut affected leaves with sterile scissors 1 inch below visible lesion; seal in plastic bag for trash disposal
- 3
Copper treatment: Apply copper-based bactericide/fungicide covering all leaf surfaces including undersides; repeat every 7-10 days for 4 treatments
- 4
Watering modification: Switch exclusively to bottom-watering; ensure foliage remains completely dry; water only in morning hours
- 5
Airflow enhancement: Position fan 3-4 feet away running 6+ hours daily to accelerate leaf drying and prevent spore germination
- 6
Environmental correction: Reduce humidity to 50-60% if above 70%; increase light to 2000-4000 lux to strengthen tissue resistance
Keep fungal infection leaf spot off this Begonia
Water at soil level only; never splash water on leaves; avoid working with wet plants; sterilize tools between plants; remove fallen debris promptly; quarantine new plants 14 days; maintain strong air circulation; avoid overhead watering even when fertilizing