Diagnosing Yellow Spots on Ficus: Fungal Anthracnose or Environmental Stress?

Observations

Braided Ficus benjamina (8 stems, 5 ft) in a 12" clay pot. White salt deposits on pot exterior. Weekly feeding with Peter's fertilizer triggered prolific new growth. Tiny yellow dots on old and new leaves, moving from tip inward. No webbing, sticky residue, or scale visible.

Possible Causes

Fungal Anthracnose

Caused by Glomerella cingulata or Colletotrichum spp. Lesions enlarge, develop a halo, turn black, and leaves drop. Monitor for these signs.

Environmental / Nutritional

Leaf spots can be transient, fading as the plant adapts to better conditions. Your feeding regimen may lack micronutrients (Mg, Ca, Fe).

Action Plan

1. Watch lesions: if they grow with halos, treat as fungal.
2. Add micronutrients: Epsom salts (1 tbsp/gal) for magnesium; iron tablets (e.g., FemIron) dissolved in water for iron.
3. If fungal: remove affected leaves, burn them. Water from bottom only to avoid splashing spores.
4. Consider sulfur-based fungicides if spread continues.