Coccomyces leaf spot

Coccomyces leaf spot is a fungal disease caused by the pathogen Coccomyces papillatus (synonym Blumeriella jaapii). This pathogen is widely recognized as a serious threat to stone fruit crops, particularly cherry and sour cherry trees, causing significant foliage loss during the growing season.

The host range of this fungus primarily includes species within the Prunus genus. In intensive orchards, if not properly managed, this disease can lead to premature defoliation, which severely stresses the trees and negatively affects the development of fruit buds for the following year.

Symptoms begin as small, purplish to dark brown spots on the upper leaf surface. Under humid conditions, white to yellowish spore masses emerge from these spots on the undersides of the leaves. As the infection progresses, leaves turn yellow and eventually fall, leaving branches bare long before autumn dormancy.

The development of the fungus is strictly dependent on moisture. Rain splashes and wind disperse the spores from the previous year's infected leaves that persist on the ground. Optimal infection occurs during wet periods with moderate temperatures, making orchards with poor air circulation particularly vulnerable.

Effective control strategies involve a combination of orchard hygiene and chemical intervention. Removing and destroying fallen leaves reduces the primary inoculum source for the following spring. Fungicide sprays, particularly those containing copper or specialized systemic compounds, are recommended throughout the growing season to prevent secondary outbreaks.

• Sanitary removal of infected foliage
• Improving air circulation via pruning
• Application of copper-based fungicides
• Timely fungicide applications post-harvest