Diaporthe citri

Systematic position and pathogen type: Diaporthe citri (anamorph stage Phomopsis citri) belongs to the kingdom Fungi, phylum Ascomycota. It is a significant phytopathogen responsible for various diseases in citrus crops, characterized by its ability to penetrate plant tissues and cause systemic damage to woody parts and fruits.

Diseases and host crops: This fungus primarily infects members of the Citrus genus, including lemons, oranges, grapefruit, and mandarins. The most economically damaging conditions caused by this pathogen are citrus melanosis, which affects fruit appearance, and phomopsis stem-end rot and branch dieback.

Biology and life cycle: The fungus survives in infected dead twigs, bark, and mummified fruits. Conidia are produced in pycnidia and are disseminated primarily by water splashes during rainfall or overhead irrigation. Once they land on susceptible tissue, they germinate and colonize the epidermal cells, often remaining latent until fruit maturation or stress occurs.

Conditions for development and harmfulness: Development is favored by warm, humid climates, particularly when temperatures range from 20°C to 25°C with high relative humidity. The economic impact is severe, as it leads to significant cosmetic damage to fruit skins, reducing their market value, and causes twig dieback that weakens the overall vitality of the tree.

Protection and control measures: Disease management requires a combination of cultural and chemical tactics:

• Rigorous pruning of dead or infected branches to reduce inoculum sources.
• Sanitation by removing fallen leaves and discarded fruits from the orchard floor.
• Application of protective copper-based fungicides during bloom and periods of high rainfall.
• Improving tree canopy ventilation to reduce leaf wetness duration, which inhibits fungal spore germination.