Apricot chlorotic leaf roll

Apricot chlorotic leaf roll is a severe disease caused by the phytoplasma Candidatus Phytoplasma prunorum, formerly classified as the agent of European Stone Fruit Yellows (ESFY). This systemic infection colonizes the phloem of host trees, leading to chronic decline and significant physiological disruptions within the plant's vascular system.

The disease primarily targets stone fruit species, with apricot and peach being highly susceptible. It is also found in plums, almonds, and myrobalans. The pathogen acts as a systemic parasite, spreading throughout the entire tree and eventually preventing proper nutrient transport between the canopy and the root system.

Clinical symptoms often appear in early spring, characterized by premature leaf development and distinct chlorosis. Leaves may become thick, leathery, and cupped. A hallmark sign is the proliferation of axillary buds, resulting in the formation of dense clusters of thin shoots, often referred to as "witches' brooms." Furthermore, the infected trees frequently exhibit significant root decay and necrotic areas.

Transmission of the disease occurs mainly through two pathways: the introduction of infected plant material (nursery stock or grafting wood) and the activity of insect vectors, specifically psyllids like Cacopsylla pruni. These insects acquire the phytoplasma by feeding on infected plants and transmit it to healthy hosts during subsequent feeding cycles.

Management of this disease is strictly preventative because there are no curative treatments available for infected trees. Effective control relies on:

• Planting certified pathogen-free nursery stock.
• Implementing strict quarantine and monitoring programs for insect vectors.
• Prompt eradication and destruction of symptomatic trees to eliminate inoculum sources.
• Regular disinfection of pruning tools to prevent mechanical transmission.