“Sharka,” also known as Plum Pox Virus (PPV), is a serious viral disease affecting stone fruit trees, particularly plum, peach, apricot, and cherry trees. PPV is considered one of the most economically important viral diseases of stone fruit trees worldwide due to its ability to cause severe yield losses and reduce fruit quality. The disease is caused by the Plum pox virus, which belongs to the Potyviridae family.

Symptoms:

1. Fruit symptoms: Infected fruit may exhibit various symptoms, including ringspots, mottling, color break, and deformation. Fruit may develop characteristic ringspots or line patterns on the surface, which can vary in size and severity depending on the cultivar and strain of PPV.
2. Leaf symptoms: Leaves of infected trees may show chlorotic (yellowing) spots or ringspots, leaf mottling, vein clearing, and leaf distortion. Symptoms can vary depending on the host plant species, cultivar, and viral strain.
3. Shoot symptoms: Infected trees may exhibit shoot dieback, stunting, and overall reduced vigor. Shoots may be distorted, with shortened internodes and small, narrow leaves.
4. Fruit drop: Severe infections of PPV can lead to premature fruit drop and reduced fruit yield, impacting the economic viability of stone fruit orchards.

Causes:

Plum pox virus is primarily spread through grafting, budding, and mechanical transmission by aphids. Aphids, particularly species in the genus Myzus (e.g., green peach aphid), can acquire the virus when feeding on infected plant tissues and subsequently transmit it to healthy trees during feeding activities. The virus can also spread through the movement of infected plant material, such as nursery stock, pruning tools, and equipment.

Recommendations and Preventive Measures:

1. Virus-free planting material: Start with certified virus-free planting material from reputable nurseries to minimize the risk of introducing PPV into orchards or gardens.
2. Sanitation: Practice good sanitation by removing and destroying infected plant material, including symptomatic fruit, leaves, and branches, to reduce the spread of PPV within orchards or gardens.
3. Vector control: Manage populations of aphid vectors through cultural practices, such as weed control, and insecticide applications to reduce the spread of PPV. Early-season control of aphids is particularly important to prevent virus transmission.
4. Monitoring: Regularly monitor stone fruit trees for symptoms of PPV, including fruit abnormalities, leaf mottling, and shoot dieback. Early detection allows for prompt intervention and management to limit the spread of the virus.
5. Rogueing: Remove and destroy infected trees to prevent the spread of PPV within orchards or gardens. This includes removing symptomatic trees as well as asymptomatic carriers of the virus.
6. Quarantine measures: Implement quarantine measures to restrict the movement of stone fruit trees, fruit, and plant material from areas known to be affected by PPV. This helps prevent the introduction and spread of the virus to new locations.
7. Research and education: Support research efforts to develop resistant cultivars, improve diagnostic methods, and develop effective control strategies for PPV. Education and outreach programs can also help raise awareness among growers and stakeholders about the importance of disease management and prevention.

By implementing these preventive measures and practicing integrated pest management, growers can help reduce the incidence and impact of PPV in stone fruit orchards and gardens. Combining cultural practices, vector control, and vigilant monitoring can help mitigate the spread of the virus and protect stone fruit trees from infection.