Impact and Management of Sharka Disease (PPV) in Latin American Stone Fruits

Molecular and Serological Identification of Plum Pox Virus (PPV)

The Sharka disease, caused by the Plum Pox Virus (PPV), represents a significant threat to stone fruit production globally, affecting key regions in Latin America. This viral pathogen, which impacts species of the genus Prunus such as plums, peaches, apricots, almonds, and cherries, causes substantial economic losses due to reduced fruit quality and quantity, as well as decreased tree longevity. Understanding its nature and implementing effective management strategies are crucial for safeguarding the profitability and sustainability of fruit farming operations.

Early detection of PPV is critical for its control. Symptoms vary depending on the fruit species, variety, viral strain, and environmental conditions. On leaves, chlorotic rings, mosaic patterns, deformities, and vein clearing are commonly observed, which may be more evident in spring. Affected fruits exhibit ring spots or necrotic lines, deformities, irregular ripening, and in some cases, gumming in the pulp, drastically reducing their commercial value. Seeds of infected fruits can also show necrotic rings.

For accurate diagnosis, laboratory methods are employed. Serological techniques, such as enzyme-linked immunosorbent assay (ELISA), allow for the detection of viral proteins. Molecular techniques, like reverse transcription polymerase chain reaction (RT-PCR), identify the virus’s genetic material with high specificity and sensitivity, being essential for the certification of plant material. Recent innovations include the development of rapid diagnostic kits based on immunochromatography and next-generation sequencing, which enable the identification of viral strains and the monitoring of the pathogen’s genetic diversity. These advancements are vital for national phytosanitary programs, such as those implemented by the National Agrifood Health and Quality Service (SENASA) in Argentina, which aim to contain the spread of the disease.

Vector Management and Viral Reservoir Elimination

The management of Sharka is primarily based on prevention, given the absence of a cure once a tree is infected. The first and most important measure is the use of certified virus-free plant material for new plantings. This includes nursery plants, buds, and rootstocks sourced from reliable suppliers who have undergone rigorous phytosanitary controls.

Vector control is another fundamental strategy. Aphids (Aphididae) are the primary transmitters of PPV, acquiring the virus from infected plants and spreading it to healthy ones. Managing aphid populations through the use of selective insecticides, biological control with natural enemies (such as ladybugs and hoverflies), and the implementation of physical barriers can reduce the infection rate. Cultural practices also play a role: constant monitoring of orchards to quickly identify and remove (uproot) symptomatic trees is crucial to prevent the spread of the virus within the orchard. Although pruning affected branches can temporarily reduce the viral load, it does not eradicate the virus from the tree.

A specific Integrated Pest Management (IPM) program for PPV coordinates all available strategies to achieve sustainable control. This involves coordination between variety selection, vector control, removal of infected plants, and compliance with phytosanitary legislation. Regulatory bodies, such as quarantine services, play a vital role in preventing the introduction and spread of the virus to new areas, establishing containment zones and eradication programs.

Development of PPV-Resistant and Tolerant Varieties

Current research focuses on developing PPV-resistant or tolerant varieties. Conventional breeding techniques and biotechnology, including gene editing with tools like CRISPR-Cas9, are being used to introduce resistance genes into stone fruit cultivars. These advancements promise long-term solutions for producers. Similarly, constant monitoring through aphid trap networks and the use of viral dispersal predictive models, often supported by digital platforms and sensors, are transforming disease management. The integration of these approaches aligns with the principles of sustainable agriculture and the resilience of production systems against emerging pathogens, an increasingly relevant aspect in the context of climate change and globalization, as promoted by agricultural research institutions like INTA in Argentina.

The economic impact of the Sharka virus is considerable, manifesting in reduced yields, depreciation of fruit quality, and the consequent decrease in producer income. Added to this are the costs associated with control measures, the removal and replacement of infected trees, and the loss of investment in young plantations. The disease can drastically shorten the productive life of orchards, forcing costly and disruptive renewals.

To mitigate these losses, it is imperative that producers stay informed about the latest management recommendations and receive support through public policies that facilitate access to certified plant material and diagnostic technologies. Regional cooperation, especially among countries sharing borders and markets, is essential for effective cross-border phytosanitary management. Looking ahead, continued research into varietal resistance and the development of more efficient and ecological management strategies will be key to ensuring the viability of stone fruit production against this persistent threat.

Economic Impact and Regional Mitigation Strategies

Effective management of the Sharka virus demands a multifaceted and proactive approach. The combination of accurate diagnostics, rigorous implementation of preventive and cultural measures, and the integration of technological and legislative innovations are crucial to mitigate its impact. Investment in research and a commitment to regional phytosanitary health are pillars for ensuring the vitality of stone fruit orchards and the long-term prosperity of producers.