Citrus Brown Rot

Phytophthora citrophthora is a significant oomycete pathogen responsible for citrus brown rot and root rot, causing severe economic losses in citrus production worldwide. This pathogen is highly adaptable and can infect various parts of the plant, from root systems to ripening fruits.

The disease primarily impacts commercial citrus crops such as lemons, oranges, and grapefruit. It is particularly devastating in orchards with poor drainage or in regions experiencing heavy rainfall, as the pathogen thrives in water-saturated environments.

The main symptoms include trunk gummosis, where lesions form on the bark and exude sap, and the eventual decay of the roots and root crown. Leaves typically show signs of yellowing (chlorosis) and wilt, eventually leading to tree decline. Infected fruits develop dark, firm, leathery patches that are often accompanied by a pungent, distinctive odor.

The spread of the pathogen is facilitated by the mobility of zoospores, which travel through irrigation water and rain splash. These spores enter the plant tissue through natural openings or physical wounds, especially on low-hanging branches that are close to the soil surface, which serves as a reservoir for the pathogen.

Effective management requires an integrated approach. Essential practices include installing proper drainage, pruning low-hanging branches to prevent soil contact, and applying copper-based fungicides or systemic chemical treatments to the trunk and soil. Maintaining tree vigor through balanced nutrition also helps the plant withstand potential infection.

• Improving soil drainage systems.
• Applying copper-based fungicide sprays.
• Pruning branches to ensure air circulation.
• Monitoring soil moisture levels consistently.