Pezicula bark rot

Pezicula malicorticis is a filamentous fungus belonging to the family Dermateaceae. As a serious plant pathogen, it is responsible for "bull's eye rot" (also known as perennial canker) in apples and pears. This fungus affects both the woody parts of the tree, leading to cankerous lesions, and the harvested fruit, causing significant economic losses during storage.

The disease is characterized by the formation of sunken, necrotic spots on the bark, which eventually expand into deep cankers. On fruits, the fungus produces light-colored circular spots with a dark center, resembling a bull's eye. The pathogenicity of this fungus lies in its ability to colonize host tissues rapidly and release spores that contaminate entire fruit batches during the handling process.

The life cycle of the pathogen involves the production of conidia and ascospores throughout the growing season. The fungus survives the winter primarily as mycelium in the cankers on bark or within infected fruit mummies. When weather conditions become favorable, these structures produce spores that are splashed by rain or wind-dispersed to healthy tissues, often entering through pruning wounds or lenticels.

Environmental conditions such as cool, wet weather, particularly during autumn, are highly conducive to the spread and infection of Pezicula malicorticis. High humidity levels in the orchard canopy facilitate the germination of spores. Furthermore, trees that have suffered winter injury or mechanical damage are particularly vulnerable to infestation by this opportunistic fungus.

Effective management and control strategies for the pathogen include:

• Meticulous pruning of cankered limbs and removal of diseased wood from the orchard.
• Removing and destroying all fruit mummies from trees and the orchard floor.
• Application of protective fungicides during the pre-harvest period and immediately after harvest.
• Sanitizing pruning tools with appropriate disinfectants to prevent cross-contamination.
• Maintaining tree vigor through balanced nutrition and proper orchard spacing to encourage airflow.