Raspberry ascospore dieback

Raspberry ascospore dieback is a fungal disease caused by Ascospora ruborum. It is a member of the Ascomycota phylum and is responsible for significant damage to commercial and home raspberry plantations.

The life cycle of the pathogen begins with the overwintering of the fungus in infected canes. As temperatures rise in spring, the fungus produces spores that are spread by rain and wind to young growth.

High humidity and moderate temperatures are the primary drivers for the spread of this pathogen. If these conditions persist during the early vegetative stage, the infection can spread rapidly.

The fungus penetrates plant tissues, primarily through wounds or buds, disrupting the vascular system of the canes. This leads to restricted nutrient flow and eventual tissue death.

Without proper management, the pathogen can persist in the soil and on crop debris for several seasons, posing a continuous threat to the health and productivity of the raspberry patch.

The primary hosts for this pathogen are members of the Rubus genus. Raspberry canes, leaf petioles, and buds are the most susceptible parts of the plant to this infection.

Initial symptoms include the appearance of purplish or brown spots centered around leaf nodes. As the infection progresses, these lesions expand and wrap around the stem.

The infected bark will eventually crack and peel, giving the canes a withered appearance. Tiny black fruiting bodies often emerge on the surface of dead tissue, indicating the presence of spores.

Cultural control practices are essential, including pruning and destroying infected canes immediately after harvest. Improving air circulation by thinning out excess canes is also critical.

Application of fungicides during the green-tip stage and after harvest can significantly reduce the infection pressure. Rotating chemical classes is recommended to prevent the development of resistance.