Cherry leaf spot

Cherry leaf spot, caused by the fungus Blumeriella jaapii, is a destructive disease affecting stone fruits, particularly cherries and sour cherries. This pathogen attacks the foliage, causing premature defoliation, which severely weakens the trees and reduces their winter hardiness and future fruit production.

The host range of this fungus primarily includes species within the Prunus genus. While leaf tissue is the most common site of infection, the fungus can also infect fruit pedicels and young green shoots under conditions of high humidity and moderate temperatures, leading to significant economic losses in commercial and home orchards.

Initial symptoms are characterized by small purple-red spots on the upper leaf surface. As the infection progresses, these spots expand, often turning brown or black. On the underside of the leaves, white or pinkish masses of spores become visible. Infected leaves eventually turn yellow and drop prematurely, often leaving the branches bare by mid-summer.

The fungus overwinters primarily in infected leaves on the orchard floor. In the spring, when temperatures rise and rain occurs, apothecia release ascospores, which are spread by wind and water splashing onto the foliage. Subsequent cycles of infection are driven by conidia, which can spread the disease rapidly throughout the growing season.

• Sanitation by raking and removing fallen leaves in autumn.
• Tilling the soil under the canopy to bury overwintering inoculum.
• Applying protective copper-based fungicides during the dormant season.
• Implementing a regular spray program with systemic fungicides post-bloom.
• Pruning trees to improve canopy airflow and reduce leaf wetness duration.