Cherry leaf scorch

The disease is caused by the ascomycete fungus Apiognomonia erythrostoma, which specifically targets stone fruit trees, with a primary preference for sour cherry. The pathogen is distinguished by its unique ability to keep infected leaves attached to the branches throughout the winter period. This makes the affected foliage a critical reservoir for the primary inoculum, which disperses to new growth at the beginning of the subsequent growing season.

Early symptoms typically appear on the foliage in late spring or early summer. Initially, small chlorotic spots develop on the leaves, which gradually turn reddish-brown or necrotic. As the infection progresses, the spots expand and may coalesce, causing the leaf tissue to wither and curl. By late summer, the infected leaves become brittle and display a characteristic "scorched" appearance, leading to premature defoliation.

Environmental factors play a decisive role in the spread of the fungus. Extended periods of high humidity, frequent rain showers, and moderate temperatures during the spring bloom are ideal for spore production and dispersal. Rain splash serves as the primary mechanism for transporting spores from the overwintering leaves on the tree to the newly developing green tissue, initiating the seasonal cycle of infection.

The economic impact of cherry leaf scorch is significant due to the reduction in the tree's photosynthetic capacity. Premature leaf drop weakens the tree, resulting in poor flower bud formation, reduced fruit size, and compromised winter hardiness. If left unmanaged, the pathogen can contribute to the gradual decline of orchards, reducing both fruit yield and the overall longevity of the trees.

Effective management strategies require an integrated approach focusing on sanitation and chemical intervention. Growers should prioritize the manual removal and destruction of infected leaves that remain on the branches during winter. Furthermore, protective fungicide applications are recommended at the green tip stage and immediately after petal fall to prevent primary infection and protect emerging foliage from fungal establishment.