Calamondin Orange Gummosis: Diagnosis and Treatment

Thick, dark exudate in small spots on a calamondin trunk suggests Phytophthora gummosis (root rot gummosis)—a fungal-like pathogen encouraged by excess moisture and warm temps (>80°F). Since your tree is indoors and leafless, it's likely early stage.

Confirming Gummosis

• Exudate is dark, oil-like, from bark cracks.
• No leaf yellowing/drop yet = early infection.
• Pathogens: Phytophthora parasitica or P. citrophthora.

Treatment Steps

1. Expose trunk and upper roots: Remove soil around base.
2. Cut away diseased bark: Trim to clean, healthy tissue.
3. Paint wounds with Bordeaux paste: Mix Bordeaux powder (copper fungicide) to thick paste; apply to cuts.
4. Build soil berm: Mound a ring of soil around excavated area to keep trunk dry during watering.
5. Maintain dry trunk zone: Keep inner berm for life of tree; keep soil below graft union.

Additional Care

• Reduce watering frequency; ensure excellent drainage.
• Apply copper fungicide as foliar spray per label for added protection.
• Monitor for leaf symptoms—yellowing means advance.

Early intervention saves citrus. This tree can recover with diligent care.