European fruit tree canker

Nectria ditissima is a destructive ascomycete fungus and a significant plant pathogen belonging to the genus Nectria. It is primarily recognized as the causative agent of European fruit tree canker, a disease that causes extensive economic losses in commercial apple and pear orchards worldwide.

The host range of this pathogen is quite broad, affecting primarily pome fruits like apples and pears. However, it also colonizes a wide variety of hardwood trees, including beech, ash, oak, and cherry, making it a persistent threat that can spread from wild forest habitats into managed horticultural environments.

The biology of the fungus involves infection through various plant entry points, such as leaf scars, pruning wounds, fruit stalk attachments, and frost cracks. The pathogen completes its life cycle by producing both ascospores and conidia, which are efficiently dispersed by wind and rain splashes during wet conditions throughout the growing season.

Development and spread are strongly favored by high humidity, rainfall, and moderate temperatures. In the autumn, leaf scars become particularly vulnerable as they provide ideal infection sites. Once established, the fungus grows within the bark and cambium, extending the canker as the tree attempts to create callus tissue, which the fungus then repeatedly breaches.

The damage caused by this pathogen includes sunken, open, or closed cankers on branches and stems, leading to reduced yield, branch dieback, and eventual tree death. Control strategies rely heavily on cultural practices, such as removing infected wood, using clean pruning tools, and applying protective copper-based fungicides during the dormant period to minimize primary infection.

• Regular inspection and pruning of infected wood.
• Sterilization of pruning equipment between trees.
• Protection of fresh wounds with wound sealants.
• Application of autumn and spring fungicide sprays.