European stone fruit yellows

European Stone Fruit Yellows (ESFY) is a destructive plant disease caused by the phytoplasma Candidatus Phytoplasma prunorum. As a phloem-restricted pathogen, it disrupts the translocation of assimilates, leading to severe physiological dysfunction, decline, and eventual death of the affected fruit trees.

The disease primarily impacts various species within the Prunus genus. Apricot, peach, and Japanese plum are highly susceptible. The economic impact is significant as infected trees become unproductive, and the disease often spreads throughout the orchard if left unmanaged.

Symptomatology typically includes early bud break, leaf curling, and distinctive yellowing (chlorosis) of the foliage. During the growing season, infected branches may develop excessive lateral shoots, resulting in a broom-like appearance. Fruit production on affected trees is often drastically reduced in both quantity and quality.

Transmission occurs primarily through the feeding activities of the psyllid vector Cacopsylla pruni. Once the insect acquires the phytoplasma from an infected tree, it can transmit the pathogen to healthy ones during subsequent feeding. Additionally, long-distance transmission is facilitated by the movement of infected nursery stock.

Management of ESFY requires a strictly preventative approach since no chemical treatments can cure an infected tree. Best practices for control include:

• Utilizing only certified, pathogen-free nursery planting material.
• Implementing integrated pest management (IPM) to control psyllid vector populations.
• Aggressive roguing of symptomatic trees to eliminate primary sources of inoculum.
• Monitoring the orchard perimeter to identify and remove potential wild Prunus hosts that may harbor the pathogen.