NE1006: Eradication, Containment and/or Management of Plum Pox Disease (Sharka)
Statement of Issues and Justification
Plum pox disease or "Sharka" is one of the most devastating and economically important diseases of stonefruit worldwide. The disease is caused by the Plum Pox Virus (PPV) which is naturally spread by several species of aphid. Although the virus is endemic to Eastern Europe it has been spread throughout Europe, the Mediterranean region and several locations in the Western Hemisphere by the unwitting use of infected propagation material. The first report of PPV in North America came from a peach orchard in Adams County Pennsylvania in 1999 and in the summer of 2000 it was found in Ontario Canada. Extensive surveys have presumably delimited the disease situation in the U.S. and Canada but the source of virus introduction into North America still has not been identified. Most economically important species of Prunus are susceptible to PPV, including peaches, nectarines, plums, and apricots (8,21). A wild species, (Prunus spinosa), occurs widely in Europe and functions as a natural symptomless PPV reservoir making eradication of the virus impossible in many countries. The virus has a large experimental host range including 134 species of plants in 16 families that have been identified by artificial inoculation (3). The complete natural host range and the role of alternate weed hosts, in virus survival and spread is not fully known especially in countries where the virus has recently been introduced. Interstate and international cooperation is needed to either eliminate or control PPV in North America. In the U.S., PPV is currently limited to Pennsylvania with approximately 5,400 Ac of stone fruits grown on small family farms. Depending on the year, Pennsylvania ranks as the fourth or fifth largest peach producing state. In 1998 Pennsylvania peach production was 65 million bushels valued at $21 million. This does not include the value to subsidiary agricultural industries or the total value to the small communities located throughout southern Pennsylvania and Maryland that are dependent on these crops. Total peach production in the eastern U.S. encompasses about 82,000 acres with a value in 1999 of $191 million. Canada has approximately 38,000 acres of stone fruits currently threatened and the occurrence of PPV in Ontario is a direct threat to stone fruit industries in New York, Michigan, and Ohio. Movement of propagation materials between Canada and New York has already occurred, but PPV has not yet been detected in this material. Other major peach producing states, such as South Carolina and Georgia, are equally threatened by the possibility of accidental movement of infected propagation material or introduction of infectious aphids. If infected propagation materials or the virus were to reach California, the results could be devastating. California currently grows approximately 265,000 Ac of susceptible stone fruits. Unlike the situation in Pennsylvania, very large commercial orchards are grown in close proximity under ideal environmental conditions for rapid aphid spread. The total value of the stone fruit industry in the U.S. is valued at $1.8 billion annually. With the ability to curtail fruit production anywhere from 10-100%, depending on the cultivar, PPV is of serious economic concern. One of the objectives of this project is to develop the infrastructure supporting multi-state and international collaborations to solve problems associated with PPV control and to provide mechanisms for increased communication and sharing of educational and scientific information. In addition, diverse facilities are needed to study this quarantined pathogen, as well as, personnel with diverse areas of expertise. It is beyond the scope of any one agency or institution to support this diversity of needs. Because PPV is a recently introduced invasive species to North America, many personnel at State Regulatory Agencies, as well as, University and County Extension personnel are unfamiliar with Plum Pox disease. Many cultivars of peach, nectarine, plum, and apricot do not show obvious symptoms when first infected and are difficult to detect and identify when first encountered. Nevertheless, excellent tools have been developed to detect and identify PPV. One of the most practical and economical is a commercially available ELISA kit that is Plum Pox specific. A number of excellent illustrated bulletins and web-sites have also been developed to assist with identification of visual symptoms. Virtually any virology lab in the country is equipped with the basic tools that would allow participation in survey work for virus detection. Despite the extensive survey work that has taken place since PPV was first found in North America it is too early to say that all sources of infected budwood and all infected orchards have been identified. Multistate cooperation is needed to continue the search and to establish a means of surveillance for possible escapes and future infestations. Even if eradication is totally successful there remains the possibility of future introductions. Furthermore, the action taken by NE-501 to deal with the PPV problem can provide a plan of action that may be applicable to other plant viruses of quarantine concern. How the U.S. fruit industry deals with PPV will depend on many factors. If PPV is still localized near the initial infection foci, it may be possible to eradicate the disease by enforced tree removal. Whether or not this will be effective depends on whether the virus is spreading to new orchards and homeowner plantings, whether the virus has invaded wild plant species and whether local aphids are efficient PPV vectors. If infected budwood has been used for propagation of trees in areas outside the quarantine area then other foci of infection in geographically distant regions may exist. If PPV is determined to be widespread in wild plant species and/or efficient vector species is identified, then eradication of PPV becomes impossible. In this scenario, management of PPV to optimize yield and profit and reduce PPV effects will be necessary. Therefore, education of all personnel involved in the fruit industry to recognize newly arriving potential invasive fruit pathogens is needed. To prevent the reintroduction of PPV requires increased education of the dangers associated with transport of restricted plant tissues. A portion of this project is directed at developing and presenting educational programs concerning PPV and other potential foreign stone fruit pathogens to concerned members of industry and the public. Standardized controls adopted nationally are needed to prevent spread of PPV to new geographical areas. Likewise, certification standards are needed to guarantee PPV-free production, transport, and sale of nursery stock and budwood. Even if PPV is eradicated within the next few years, there is a high probability that reintroduction will occur in the future. Alternatively if PPV becomes established in the U.S., it must be controlled to economically acceptable levels. One objective of this project will be to develop standards for PPV testing and certification of nursery stock among states. A portion of the research effort in this program will be directed at understanding how PPV spreads from orchard to orchard within growing regions and how the virus and its vectors survive overwinter. This information will be used in development of epidemiological models to understand how to control the disease and in the development of disease management systems (Decision Support Systems). The objectives for this proposal were developed during a meeting of participants in the NE-501 Northeastern Multistate Research Project entitled, "Eradication, Containment, and/or Management of Plum Pox (Sharka) Disease" held Oct. 31 to Nov. 1, 2000, in Gettysburg PA. Participants included major stone fruit growers in Adams County, PA, stone fruit nursery owners in Adams Co., county extension agents, fruit specialists and researchers from 18 major stone fruit growing states, and representatives from several state and federal regulatory agencies. Plum pox disease or "Sharka" is one of the most devastating and economically important diseases of stonefruit worldwide. The disease is caused by the Plum Pox Virus (PPV) which is naturally spread by several species of aphid. Although the virus is endemic to Eastern Europe it has been spread throughout Europe, the Mediterranean region and several locations in the Western Hemisphere by the unwitting use of infected propagation material. The first report of PPV in North America came from a peach orchard in Adams County Pennsylvania in 1999 and in the summer of 2000 it was found in Ontario Canada. Extensive surveys have presumably delimited the disease situation in the U.S. and Canada but the source of virus introduction into North America still has not been identified.Most economically important species of Prunus are susceptible to PPV, including peaches, nectarines, plums, and apricots (4,11,13). A wild species, (Prunus spinosa), occurs widely in Europe and functions as a natural symptomless PPV reservoir making eradication of the virus impossible in many countries. The virus has a large experimental host range including 134 species of plants in 16 families that have been identified by artificial inoculation (1). The complete natural host range and the role of alternate weed hosts, in virus survival and spread is not fully known especially in countries where the virus has recently been introduced.
Interstate and international cooperation is needed to either eliminate or control PPV in North America. In the U.S., PPV is currently limited to Pennsylvania with approximately 5,400 Ac of stone fruits grown on small family farms. Depending on the year, Pennsylvania ranks as the fourth or fifth largest peach producing state. In 1998 Pennsylvania peach production was 65 million bushels valued at $21 million. This does not include the value to subsidiary agricultural industries or the total value to the small communities located throughout southern Pennsylvania and Maryland that are dependent on these crops. Total peach production in the eastern U.S. encompasses about 82,000 acres with a value in 1999 of $191 million. Canada has approximately 38,000 acres of stone fruits currently threatened and the occurrence of PPV in Ontario is a direct threat to stone fruit industries in New York, Michigan, and Ohio. Movement of propagation materials between Canada and New York has already occurred, but PPV has not yet been detected in this material. Other major peach producing states, such as South Carolina and Georgia, are equally threatened by the possibility of accidental movement of infected propagation material or introduction of infectious aphids. If infected propagation materials or the virus were to reach California, the results could be devastating. California currently grows approximately 265,000 Ac of susceptible stone fruits. Unlike the situation in Pennsylvania, very large commercial orchards are grown in close proximity under ideal environmental conditions for rapid aphid spread. The total value of the stone fruit industry in the U.S. is valued at $1.8 billion annually. With the ability to curtail fruit production anywhere from 10-100%, depending on the cultivar, PPV is of serious economic concern. One of the objectives of this project is to develop the infrastructure supporting multi-state and international collaborations to solve problems associated with PPV control and to provide mechanisms for increased communication and sharing of educational and scientific information. In addition, diverse facilities are needed to study this quarantined pathogen, as well as, personnel with diverse areas of expertise. It is beyond the scope of any one agency or institution to support this diversity of needs.
Because PPV is a recently introduced invasive species to North America, many personnel at State Regulatory Agencies, as well as, University and County Extension personnel are unfamiliar with Plum Pox disease. Many cultivars of peach, nectarine, plum, and apricot do not show obvious symptoms when first infected and are difficult to detect and identify when first encountered. Nevertheless, excellent tools have been developed to detect and identify PPV. One of the most practical and economical is a commercially available ELISA kit that is Plum Pox specific. A number of excellent illustrated bulletins and web-sites have also been developed to assist with identification of visual symptoms. Virtually any virology lab in the country is equipped with the basic tools that would allow participation in survey work for virus detection.
Despite the extensive survey work that has taken place since PPV was first found in North America it is too early to say that all sources of infected budwood and all infected orchards have been identified. Multistate cooperation is needed to continue the search and to establish a means of surveillance for possible escapes and future infestations. Even if eradication is totally successful there remains the possibility of future introductions. Furthermore, the action taken by NE-501 to deal with the PPV problem can provide a plan of action that may be applicable to other plant viruses of quarantine concern.
How the U.S. fruit industry deals with PPV will depend on many factors. If PPV is still localized near the initial infection foci, it may be possible to eradicate the disease by enforced tree removal. Whether or not this will be effective depends on whether the virus is spreading to new orchards and homeowner plantings, whether the virus has invaded wild plant species and whether local aphids are efficient PPV vectors. If infected budwood has been used for propagation of trees in areas outside the quarantine area then other foci of infection in geographically distant regions may exist. If PPV is determined to be widespread in wild plant species and/or efficient vector species is identified, then eradication of PPV becomes impossible. In this scenario, management of PPV to optimize yield and profit and reduce PPV effects will be necessary.
Therefore, education of all personnel involved in the fruit industry to recognize newly arriving potential invasive fruit pathogens is needed. To prevent the reintroduction of PPV requires increased education of the dangers associated with transport of restricted plant tissues. A portion of this project is directed at developing and presenting educational programs concerning PPV and other potential foreign stone fruit pathogens to concerned members of industry and the public.
Standardized controls adopted nationally are needed to prevent spread of PPV to new geographical areas. Likewise, certification standards are needed to guarantee PPV-free production, transport, and sale of nursery stock and budwood. Even if PPV is eradicated within the next few years, there is a high probability that reintroduction will occur in the future. Alternatively if PPV becomes established in the U.S., it must be controlled to economically acceptable levels. One objective of this project will be to develop standards for PPV testing and certification of nursery stock among states. A portion of the research effort in this program will be directed at understanding how PPV spreads from orchard to orchard within growing regions and how the virus and its vectors survive overwinter. This information will be used in development of epidemiological models to understand how to control the disease and in the development of disease management systems (Decision Support Systems).
The objectives for this proposal were developed during a meeting of participants in the NE-501 Northeastern Multistate Research Project entitled, "Eradication, Containment, and/or Management of Plum Pox (Sharka) Disease" held Oct. 31 to Nov. 1, 2000, in Gettysburg PA. Participants included major stone fruit growers in Adams County, PA, stone fruit nursery owners in Adams Co., county extension agents, fruit specialists and researchers from 18 major stone fruit growing states, and representatives from several state and federal regulatory agencies. Participants from the Ontario Ministry of Agriculture and the Canadian Food Inspection Service also participated. Following the first day of research reports, the second day was dedicated to workshop sessions in which all attendees (approx.100), including growers, and nursery representatives also participated in a USDA sponsored meeting held in Harrisburg, PA in Dec. 1999 to develop priorities for PPV control. The objectives of this proposal were derived from these extensive discussions and meetings among all stakeholders in the stone fruit industry.
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