Apple scab

Apple scab is a destructive fungal disease caused by the pathogen Spilocaea pomi (syn. Venturia inaequalis). It primarily affects the domestic apple tree, impacting orchard productivity and significantly reducing the market value of the fruit crop.

The first signs of infection typically appear on leaves and blossoms in early spring. These symptoms manifest as olive-green, velvety spots that eventually turn dark brown or black. As the disease progresses, the infected tissue may become brittle, leading to premature leaf drop.

Fruit damage is particularly severe, characterized by round, corky, dark-colored lesions on the skin. Severely infected apples often show deformation and cracking, which not only ruins their appearance but also creates entry points for secondary infections during storage.

The development of the fungus is highly dependent on humidity and temperature. Rainfall events, particularly in spring, trigger the release of ascospores from overwintering infected leaves, which are then carried by wind or water to susceptible plant tissues, initiating the infection cycle.

Integrated pest management (IPM) is essential for control. Effective strategies include the removal of leaf litter to reduce primary inoculum, regular pruning to improve air circulation, and a preventive fungicide spray program timed according to the tree's growth stages.

• Sanitation: removing fallen leaves to break the disease cycle.
• Cultural practices: planting resistant cultivars and pruning for canopy airflow.
• Chemical control: using fungicides during high-risk rainy periods.