Didymella fruit spot

The causative agent of this disease is the fungus Didymella pomorum. This pathogen is known to cause localized infections on pome fruits. It is primarily identified as a fungus that leads to fruit spotting, which can severely compromise the quality of the harvest if not managed properly during the growing season.

The main host for this fungus is the apple tree. While it is less common on other orchard crops, the impact on apple production is significant. The fungus attacks the fruit surface, taking advantage of the natural susceptibility of ripening apples, especially in dense or poorly managed orchard canopies.

Symptoms appear as distinct spots on the surface of the fruit. These spots are initially reddish or brown and may gradually darken as the fungal growth progresses. Over time, small black structures called pycnidia, which are the reproductive organs of the fungus, can be observed within the infected lesions, confirming the diagnosis.

• High ambient humidity and persistent rainfall during late summer.
• Temperatures optimal for fungal growth, typically between 18°C and 25°C.
• Mechanical damage or insect stings on the fruit skin providing entry points.
• Poor air circulation due to dense tree foliage.

The economic impact of the disease is largely due to post-harvest losses. Infected fruits are not only unsightly but also serve as focal points for further decay in cold storage. Because the pathogen spreads through spores, a few infected apples can quickly lead to widespread rot in a storage environment if not sorted properly.

Effective prevention strategies include rigorous sanitation practices in the orchard, such as removing mummified fruits and leaf debris, which serve as overwintering sites for the fungus. Pruning to ensure proper canopy airflow is crucial. During the growing season, timely applications of approved fungicides are necessary, and maintaining ideal temperature and humidity levels in storage is essential to prolong fruit shelf life.