Citrus gummosis

Citrus gummosis is a destructive plant disease primarily caused by soil-borne fungi of the Phytophthora genus. The disease specifically targets the bark of the trunk and the root crown, often leading to restricted nutrient transport and systemic decline of the tree if left untreated.

A wide range of citrus species, including lemons, sweet oranges, and grapefruits, are susceptible to this infection. Vulnerability is often exacerbated by environmental stressors and the use of incompatible rootstocks that lack resistance to fungal pathogens.

The hallmark symptom of gummosis is the exudation of viscous, amber-colored sap (gum) from the bark. As the disease progresses, the affected bark may develop longitudinal cracks, appear water-soaked, and eventually die and slough off, exposing the underlying woody tissue to environmental damage and secondary pathogens.

The development and spread of gummosis are heavily dependent on moisture levels. High soil humidity, poor drainage, and injury to the trunk base provide ideal entry points for the pathogen. Once established, the fungus thrives in stagnant water and humid conditions, rapidly colonizing the plant's vascular tissue.

Effective management and prevention strategies include the following steps:

• Surgical removal of diseased bark tissue until healthy green layers are reached.
• Application of copper-based fungicides to the exposed, sterilized wounds.
• Improving soil drainage to ensure the root crown remains dry.
• Avoiding deep planting and mechanical damage to the trunk base during weeding or lawn maintenance.