© 2012 Plant Management Network. Accepted for publication 23 May 2012. Published 23 July 2012. An Epidemiological Comparison of the US and Canadian Plum pox virus Eradication Programs A. V. Gougherty and F. W. Nutter, Jr., Department of Plant Pathology, 351 Bessey Hall, Iowa State University, Ames, IA 50011 Corresponding author: Forrest W. Nutter, Jr. fwn@iastate.edu Gougherty A. V., and Nutter, F. W., Jr. 2012. An epidemiological comparison of the US and Canadian Plum pox virus eradication programs. Online. Plant Health Progress doi:10.1094/PHP-2012-0723-03-RS. Abstract Plum pox virus (PPV) was first detected in North America in 1999 in Pennsylvania, and the following year in Ontario, Canada. In response to these outbreaks, both countries implemented eradications programs in an effort to eradicate the virus before it could have a significant effect on the Prunus industry in their respective countries. The objectives of this study were to: (i) quantify the impact of the US and Canadian PPV eradication programs on the spatial and temporal dynamics of PPV in Pennsylvania and Ontario; and (ii) compare the detection efficiencies of the US and Canadian PPV sampling systems. Ripley’s K function revealed PPV-positive Prunus blocks in Pennsylvania to be clustered between distances of 0.7 and 4.3 km in 2000, while in Ontario, PPV-positive blocks were clustered between distances of 1 and 25 km over the period 2006-2009. A simulation model was developed to determine the relative detection efficiencies of the US and Canadian PPV eradication programs. The US eradication program was found to have a detection efficiency of 71.7%, whereas the Canadian eradication program had a detection efficiency of 40.5%. The data generated in this study should help to improve the PPV eradication programs currently used in the US and Canada, as well as provide a scientific basis to evaluate future eradication programs. Introduction Plum pox virus (PPV), also known as Sharka disease, is one of the most damaging diseases of stone fruit worldwide (5). The virus was first characterized in Bulgaria in 1915 (1), and has since been detected in much of Europe as well as in Asia and South America (5). Plum pox virus was first detected in North America in Pennsylvania in 1999 (4), and in Ontario, Canada the following year (8). In response to these outbreaks, the US and Canadian governments implemented PPV survey and eradication programs with the goal of eradicating PPV before it could have a significant negative impact on the stone fruit industry in either country. The US and Canadian PPV eradication programs differed in a number ways including sample size (leaves collected per tree), testing method, and tee removal policy (eradication). In the United States, Prunus blocks in areas where PPV has not been previously detected Prunus trees for testing are sampled using a hierarchical sampling protocol whereby approximately 25% of trees within Prunus blocks are sampled and tested for PPV by ELISA (3). In areas where the virus has been previously detected (quarantine areas) all trees within Prunus blocks are sampled. In Pennsylvania, 8 leaves are collected per tree sample, and these are bulk-tested using a commercially available double antibody sandwich (DAS) enzyme linked immunosorbent assay (ELISA) test kit (Agdia Inc., Elkhart, IN). Detection efficiency is a critical element of the Pennsylvania eradication program, as all Prunus trees within 500 m of a PPV-positive tree are removed, regardless of their health status. Sampling and testing protocols in Ontario are similar to the Pennsylvania protocols, in that a hierarchical sampling design is also used in non-quarantine areas (sampling approximately 25% of trees) to sample and test Prunus trees, and a census is used in PPV-quarantine areas. However, in Ontario, 20 leaves are collected per tree sample and these 20 leaves are bulk tested using a 23 July 2012 Plant Health Progress