Citrus dry rot

Citrus dry rot is a fungal disease caused by species of the genus Eremothecium (notably Eremothecium coryli). This pathogen acts as a localized internal infection that leads to the desiccation and decay of internal citrus tissues without the extensive tissue softening typically associated with other common fruit rot diseases.

The disease primarily affects various citrus species, including lemons, oranges, and mandarins. The key biological factor in the epidemiology of this disease is its transmission vector; the fungus is typically introduced into the fruit through punctures made by sap-sucking insects, such as true bugs, which carry the spores directly into the interior of the fruit.

Symptoms appear as internal necrosis and discoloration of seeds and adjacent fruit segments. Over time, the affected areas become dry, shriveled, and necrotic. The fruit may appear normal from the outside in the early stages, but the significant decline in fruit quality and taste makes it impossible to market or process the produce, leading to substantial economic losses.

The development and spread of Eremothecium are heavily dependent on warm, humid environmental conditions, which are ideal for the activity of insect vectors. The fungus spreads most aggressively when insect populations are high, as they move from tree to tree, actively injecting the pathogen into healthy developing fruits during the growing season.

• Implementing integrated pest management (IPM) to control insect vectors.
• Sanitation practices, including the removal and destruction of dropped fruits.
• Monitoring orchards for signs of insect damage to mitigate potential fungal entry points.
• Using protective orchard coverings where feasible to exclude insect populations.

The most effective management strategy involves controlling the insect vectors that facilitate the entry of the fungus. Since the pathogen resides inside the fruit, curative chemical treatments are generally ineffective. Therefore, the focus must remain on preventative measures, such as maintaining orchard hygiene and keeping pest populations below economic injury levels through regular scouting and appropriate insecticide timing.