Peyronellaea pomorum leaf spot

The disease is caused by the fungus Peyronellaea pomorum, formerly known as Phoma pomorum. This pathogen belongs to the group of coelomycetes and is responsible for significant necrotic spots on various parts of host plants. It is classified as a foliage and fruit-rotting fungal disease affecting both agricultural and ornamental plants.

The host range of this pathogen is remarkably broad, including pome fruits like apples and pears, as well as various vegetables such as potatoes and tomatoes. Peyronellaea pomorum can persist for extended periods as a saprophyte in soil debris and on alternative hosts, maintaining its viability across growing seasons.

Symptoms typically appear as irregular or circular spots on leaves, which may turn brown or grey as the tissue dies. In advanced stages of infection, small, black, pinhead-sized pycnidia are visible on the surface of these spots, which act as fruiting bodies. In some cases, the infection can cause leaf distortion and severe chlorosis.

Development and dissemination of the pathogen are highly favored by humid and moderate weather conditions. Conidia (spores) are primary agents of transmission, spreading through rain splash, wind currents, and mechanical contact. Wounds caused by insect activity or environmental damage serve as primary entry points for the fungal mycelium into healthy tissues.

The economic impact of the disease is significant, as it leads to reduced photosynthetic efficiency, lower yields, and poor storage shelf-life of harvested fruits. Effective control measures focus on

• sanitation to remove infected debris;
• crop rotation practices;
• application of protective and systemic fungicides during critical growth stages;
• maintaining proper plant spacing to improve airflow and humidity management.