Brown rot of citrus

Brown rot of citrus, often identified by its leathery appearance on fruit skin, is a significant fungal disease caused by the pathogen Phytophthora citrophthora. This disease is a major concern for citrus growers worldwide as it impacts both tree health and the post-harvest quality of the crop.

The disease primarily affects a wide range of citrus species, including lemons, oranges, and grapefruit. The pathogen resides in the soil and, under favorable environmental conditions, can spread rapidly throughout the orchard, targeting fruit in the lower canopy that are closest to the ground.

Symptoms are marked by firm, leathery, and brown discolored spots on the fruit surface. Unlike soft rots, the internal tissue often remains relatively firm initially, although the infection quickly spreads throughout the entire fruit, emitting a pungent, off-putting odor that is characteristic of Phytophthora infections.

Development and spread of the disease are heavily dependent on wet, humid conditions. Rain splash is the primary mechanism by which the pathogen is transported from contaminated soil onto the lower-hanging fruit, especially during the ripening period when the crop is most susceptible.

Control strategies rely on a combination of cultural practices and chemical applications. Maintaining tree health and structural balance is vital, as is preventing irrigation water from splashing soil onto the canopy. Preventive spraying with copper-based fungicides remains a standard industry practice to protect the fruit from infection.

• Pruning lower branches to increase clearance from the soil.
• Improving orchard drainage to prevent water accumulation.
• Applying fungicides during periods of high rainfall.
• Implementing strict sanitation to remove infected fruit.
• Monitoring weather patterns to time protective sprays.