Control and monitoring: Plum pox virus quarantine situation in France

Sharka disease caused by Plum pox virus (PPV) is present in several areas in France, and its total eradication from the territory is not considered feasible. Although sharka falls under mandatory control measures, the objective is, in the infected areas, to contain the disease in the orchards at sufficiently low levels so that the production remains economically viable. In parallel, official controls are carried out to guarantee that plants for planting, including seedlings, which are moved in trade are free from PPV.     

Control and monitoring: phytosanitary situation of Plum pox virus in Australia

Sharka disease does not occur in Australia and is recognized as the most serious disease threat to Australia's stone fruit industry. Strategies are in place to minimize the risk that exotic diseases like sharka should establish in Australia. These are achieved by implementing: (1) pre-import measures to reduce the threat of entry; (2) controls at the point of entry and (3) response and contingency planning to contain or eradicate any incursions into Australia. An active and on-going awareness programme within the Australian stone fruit industry is aimed at early detection of sharka disease in the orchard.     

Control and monitoring: control strategies for Plum pox virus in Canada

In 2000, Plum pox virus (PPV) was discovered in Canada in the provinces of Ontario and Nova Scotia. Delimitation surveys were used to define quarantine areas. An eradication strategy was developed based on a threshold value for virus incidence which triggered removal of the entire orchard block. Each year the threshold value is being lowered until reaching a zero tolerance level. Growers are compensated financially for their losses. A two-tiered certification programme was designed to provide clean replacement trees. Initially, growers planted PPV-tested trees as an interim measure until fully virus-tested stock became available. It is hoped that this eradication programme will eliminate PPV from Canada by 2010.     

Control and monitoring: quarantine situation of Plum pox virus in New Zealand

Biosecurity New Zealand recognizes that Plum pox virus (PPV) is one of the most destructive diseases of stone fruit and aims to keep New Zealand free from it. PPV has never been detected in New Zealand orchards during national surveys. but it has been detected in post-entry quarantine. Biosecurity New Zealand has analysed the potential pathways for PPV to enter the country, and developed phytosanitary regulations and prevention control measures to reduce the risks. A contingency plan, a response programme, and diagnostic protocols have been developed and simulation exercises based on a hypothetical PPV incursion have been carried out.     

Control and monitoring: control of Plum pox virus in the United Kingdom

Plum pox virus (PPV) was first identified in the United Kingdom in 1965. Despite a rigorous eradication policy, the disease spread quickly and established itself in all the main plum-growing areas in England. In 1975, the policy was changed from a blanket eradication campaign to one of containment; retaining statutory control of PPV on propagation material but allowing the industry to control the disease in orchards. As part of the current containment campaign, annual surveys are carried out on propagation material. These surveys show that the incidence of PPV in this material is very low and that only the D-strain is present. The precise situation regarding PPV incidence in commercial orchards is unknown. Given the low incidence in propagation material, it is likely that PPV is uncommon in actively managed orchards. However, some infected orchards probably do still exist, especially older, unmanaged or abandoned ones. Overall, the history of PPV control in the UK is one of unsuccessful eradication but successful containment. The UK experience demonstrates that given the right combination of strain and host, alongside a regular testing regime, it is possible to control PPV through the establishment of a regulated certification scheme and the supply of virus-free planting material.     

Detection of Plum pox virus: biological methods

This paper describes biological testing techniques for Plum pox virus (PPV), focussing in particular on woody indicators such as Prunus persica (L.) Batsch GF305 and P. tomentosa (Thunb.) Wall.     

Hosts and symptoms of Plum pox virus: Herbaceous hosts

Plum pox virus (PPV) is polyphagous and epidemic. Apart from cultivated and wild Prunus species, a large number of herbaceous plants can be hosts of the virus. New herbaceous host species are continuously being reported following artificial inoculation studies. Some of these herbaceous hosts, Chenopodium foetidum , Nicotiana clevelandii , N. benthamiana and Pisum sativum are very useful for concentrating and purifying the virus. The list of plants that have been found to be infected with PPV in their natural environment is shorter than the list of plants which can be experimentally infected. The role of weed species in PPV survival and spread in orchards is poorly understood. It is widely accepted that annual plants or weeds are not important in the epidemiology of PPV.     

Detection and characterization of Plum pox virus: serological methods

Tremendous progress has been made in the research and development of Plum pox virus (PPV) serological reagents and methods in recent years. Two facts have revolutionised the serological detection and characterization of the virus: the development of the ELISA method in 1977, and the later emergence of specific monoclonal antibody technology. The availability of commercial kits has popularised PPV diagnosis, now making diagnosis possible at large scale for quarantine purposes, eradication programmes and control of the disease in nurseries. The use of the universal monoclonal antibody 5B-IVIA, used in DASI-ELISA, is the most accurate system for routine PPV detection. Likewise, the use of typing monoclonal antibodies gives exact characterization of the main PPV types described: 4DG5 for PPV-D, AL for PPV-M, EA24 for PPV-EA, and TUV and AC for PPV-C. There is, in general, an excellent correlation between serological data obtained with PPV specific monoclonal antibodies and data obtained by molecular PCR based methods. ELISA using a single or a mixture of monoclonal antibodies will remain the preferred method for universal detection and routine screening of PPV for years to come. Today, other serological methods and reagents are also recommended in the EPPO Diagnostic Protocol, increasing the number of reliable tests available for PPV detection. These developments have helped to control sharka disease in recent years. International co-operation in this field has been crucial to the improvement and validation of serological tools for PPV detection and characterization.     

Control of Plum pox virus through the use of genetically modified plants

Genetic resistance to Plum pox virus (PPV) is the most viable alternative for long-term control of sharka disease. In addition to the classical approaches to producing resistant germplasm and cultivars, genetic transformation offers a promising genetic approach to resistance. We show, using the example of C5 plum, that genetically engineered resistance can provide durable, stable and high levels of PPV resistance. A review of the results of work with C5 including molecular analyses of resistance and long-term field testing is presented.