Raspberry ascospora dieback

Taxonomy and type of pathogen: Ascospora ruborum is a fungal pathogen classified within the Ascomycota division. It serves as a specialized parasite that targets members of the Rubus genus, primarily affecting raspberries and blackberries in both commercial and home garden settings.

Diseases and host plants: The fungus is responsible for the disease commonly known as ascospora dieback or purple blotch. The infection primarily impacts canes, petioles, and fruiting spurs. If left untreated, the disease causes significant tissue necrosis, leading to weakened plant structures and reduced fruit production.

Biology and lifecycle: The pathogen survives the winter as mycelium and fruiting bodies (perithecia) on infected canes and leaf litter. During favorable conditions in the spring and summer, spores are released and dispersed by rain and wind. Once contact is made with healthy tissue, the spores germinate and penetrate the epidermis, establishing a new infection cycle.

Developmental conditions and impact: High humidity, frequent rainfall, and poor air circulation in dense plantings create an ideal environment for Ascospora ruborum to thrive. The economic damage is significant, as infected canes often experience buds dying, cracking of the bark, and general loss of winter hardiness, which can lead to the death of canes during cold weather.

Protection and control measures: Effective management of the disease requires an integrated approach:

• Sanitary pruning of all infected canes directly after harvest.
• Ensuring proper plant spacing to improve airflow and reduce humidity around the base.
• Applying fungicides during the growing season based on regional agricultural recommendations.
• Maintaining vigorous plant health through balanced nutrient management.
• Removing and destroying infected plant debris to reduce the primary inoculum load.