Cercospora leaf spot of stone fruits

The fungus Mycosphaerella pruni-persicae is the causal agent of Cercospora leaf spot, a significant pathology affecting various stone fruit species. This disease disrupts photosynthetic activity, directly impacting the tree's vigor and overall yield potential.

The host range includes important commercial crops such as peach, plum, apricot, and almond. The pathogen is particularly active in regions characterized by humid, temperate climates, where environmental conditions facilitate long-distance dispersal of fungal spores.

Early symptoms appear as small, circular, or irregular spots on leaves, which typically feature a brownish or reddish-purple hue surrounded by a darker necrotic margin. As the infection progresses, the necrotic centers may drop out, causing a shot-hole appearance and eventually leading to premature leaf drop.

High relative humidity and frequent rainfall are the primary drivers of disease development and spread. The pathogen survives the winter in leaf litter and on infected plant debris, producing inoculum in early spring that initiates the primary infection phase on newly emerged leaves.

Integrated pest management is crucial for control. Effective strategies involve sanitizing the orchard by removing infected leaves, ensuring adequate spacing between trees to improve airflow, and implementing a strict fungicide spray program. Applying protective copper-based sprays early in the season is a standard practice to mitigate the risk of severe outbreaks.