Ascochyta bark necrosis

The disease caused by the fungus Ascochyta corticola is a type of bark necrosis affecting various woody plant species. As an obligate or facultative parasite, the fungus invades the cortical tissues, disrupting the nutrient and water flow, which often leads to the death of affected branches.

The host range for this pathogen primarily includes fruit trees, particularly those within the Rosaceae family. It is most frequently encountered in neglected or mechanically damaged orchards, where bark integrity has been compromised by frost cracks, pruning wounds, or pest activities.

Symptoms of the disease are characterized by the development of depressed, brownish lesions on the bark surface. Within these necrotic areas, the fungus produces small, black, dot-like fruiting structures called pycnidia. Eventually, the affected bark may crack, become detached from the wood, and exhibit signs of dry rot.

Environmental conditions play a crucial role in the development of Ascochyta corticola. High humidity, mild temperatures, and poor air circulation within the tree canopy favor the production and release of fungal spores. Rain splashes serve as the primary mechanism for the dissemination of conidia to healthy tissues.

The impact of this disease on agricultural productivity is significant. By causing tissue death and branch dieback, the fungus weakens the tree's physiological state, leading to reduced yield and poor overall plant vigor. In severe cases, failure to manage the infection can cause systemic decline or death of the host tree.

Management and prevention focus on reducing inoculum and improving plant resilience. It is recommended to perform regular pruning to remove and destroy infected plant debris, ensuring that cuts are made into healthy tissue. Protecting wounds with appropriate sealants and applying preventive copper-based fungicides during the dormant season are standard practices to limit the spread and severity of the disease.