Leaf Spot on rubber plant
What's Happening
Leaf spot diseases in Ficus elastica appear as distinct circular, oval, or irregular lesions ranging from pinpoint to 0.5 inch diameter, often with defined margins and varying colors (tan, brown, black, or yellow halos). These differ from mechanical damage or sunburn by their patterned appearance and potential to spread across leaf surface. Bacterial leaf spot (Xanthomonas) produces water-soaked angular lesions bounded by leaf veins, while fungal leaf spot (Cercospora, Colletotrichum) shows concentric ring patterns or dark sporulating centers. Both types thrive in conditions where foliage remains wet for 6+ hours from overhead watering, poor air circulation, or high humidity without adequate light.
How to Fix It
- 1
Distinguish bacterial vs fungal spots: Bacterial spots are water-soaked, angular, and bounded by veins; fungal spots have concentric rings, fuzzy centers, or defined brown margins with yellow halos
- 2
Remove infected leaves immediately: Prune 1 inch below visible damage with sterile scissors; seal in plastic bag and discard—do not compost diseased material
- 3
Apply appropriate treatment: For bacterial spots—copper-based bactericide per label; for fungal spots—neem oil (1 tbsp/gallon + 1 tsp soap) or fungicide
- 4
Improve cultural conditions: Increase air circulation with fan on low setting; ensure bright indirect light; adjust watering to prevent foliage wetness
- 5
Prevent spread: Isolate infected plant; sterilize tools after each use; wash hands between handling plants; repeat treatment every 7-10 days for 3 applications minimum; monitor for 4-6 weeks to ensure disease is eradicated
How to Prevent It
Water at soil level only—never splash or spray foliage; maintain 12+ inch spacing between plants for air circulation; provide bright indirect light (2000+ lux) to ensure rapid leaf drying after any water contact; sanitize pruning tools with 70% alcohol between plants; avoid handling plants when foliage is wet; remove lower leaves that touch soil surface; quarantine new plants 14 days before integrating with collection; inspect plants weekly for early spot detection.