• Definition

  Gommosis is a fungal disease that affects the crown and base of the trunk of citrus trees. It is caused by fungi of the genus Phytophthora, which enter through wounds or excessive moisture at ground level. This disease manifests itself as a brownish gum (resin) discharge on the outside of the bark and necrosis of the wood underneath.

  Development Lifecycle

  1. Overwintering : The fungus survives in soil, plant debris, and dead roots as dormant spores or mycelium.

  2. Contamination : During humid conditions, spores move into soil water (rain, irrigation).

  3. Infection : Spores penetrate the tissues of the crown or trunk, especially through natural wounds or cracks.

  4. Development : The fungus destroys cortical cells, leading to bark necrosis and gum flow.

  5. Spread : Spores spread via splashes or irrigation water, which can infect other trees.

  Symptoms

  • Cracks in the bark at the base of the trunk or scion.

  • Brownish gum discharge (shiny and sticky appearance).

  • Necrosis of the wood under the bark (dark brown area visible after scraping).

  • Progressive weakening of the tree, yellowing of the leaves, premature drop.

  • In severe cases: death of the tree.

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  Contributing factors

  • • Poorly drained and overly wet soils.

    • Presence of standing water around the crown.

    • Temperatures between 20 and 30 °C.

    • Susceptible rootstocks.

    • Mechanical injuries to the trunk (clipping, tools, pruning).

    • Excessive irrigation or too close to the trunk.

Preventive control

• Use of resistant rootstocks (e.g., Poncirus trifoliata or resistant hybrids).
• Raise the graft point so that it remains above ground level.
• Improve soil drainage and avoid low areas.
• Never injure the trunk during farm work.
• Avoid irrigation directly touching the base of the trunk.

Healing control

• Scrape the necrotic bark down to the healthy wood, then apply a contact fungicide (copper-based).
• Chemical treatment with potassium phosphite or fosetyl-Al as a foliar application or injection.
• Disinfection of tools.

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