Beech leaf spot

Petrakia fagi is a specific fungal pathogen recognized as the causal agent of leaf spot disease in beech trees (Fagus sylvatica). This disease frequently affects both landscape trees and forest specimens, potentially impacting the health and aesthetic value of affected plantations.

The host range of this fungus is primarily restricted to beech species. While mature, healthy trees may tolerate the infection, young trees and saplings in nursery environments are particularly vulnerable, often suffering from reduced vigor and stunted growth due to the premature loss of foliage.

Symptoms of the disease are characterized by the appearance of distinct lesions on the leaf surface. These spots often start as small discolored areas that eventually expand, turning brown or dark grey, and are typically accompanied by a fine fungal coating on the undersides of the leaves under high humidity.

The development of the fungus is strictly tied to climatic conditions. It thrives in cool, wet, and humid environments, which facilitate the production and spread of conidia. The fungus overwinters in the leaf litter, serving as a primary inoculum source when the new leaves emerge in the spring.

Management and prevention focus on reducing inoculum pressure and enhancing tree resilience. Effective strategies include:

• Removing and destroying infected leaf litter to eliminate overwintering sites;
• Pruning to ensure adequate air circulation within the canopy;
• Applying preventive fungicide treatments in early spring if the site has a history of heavy infection.