Pacific Southwest

Title: Epidemiological modeling of Phytophthora ramorum: network properties of susceptible plant genera movements in the nursery sector of England and Wales

Author: Pautasso, Marco; Harwood, Tom; Shaw, Mike; Xu, Xiangming; Jeger, Mike

Date: 2008

Source: In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 257-264

Station ID: GTR-PSW-214

Description: Since the first finding of Phytophthora ramorum in the U.K. (on Viburnum tinus, 2002), the pathogen has been reported throughout the country on a variety of susceptible species both in the horticultural sector and in woodlands and historic gardens. The nursery network may have properties which affect the epidemic threshold for spread of the pathogen. Here, as part of ongoing modeling studies, we provide an analysis of the database of positive P. ramorum records in England and Wales (2003 to 2005), both in terms of affected plant genus and country of origin. The majority of positive findings are reported on Rhododendron (68 percent), with a substantial minority on Viburnum, Camellia, and Pieris. Another 15 genera make up the remaining 3 percent of positive records. These findings highlight the wide range of plant species at risk from the pathogen, and suggest that Rhododendron could act as a super-connected susceptible genus. This property would be characteristic of a scale-free network. As for the country of origin, the majority of findings originate from the U.K., but a non-negligible number (~ 30 percent) of positive records originate from several other countries. Models f network movements of plants susceptible to P. ramorum therefore need to take into account that this is a largely open system, with both links in and out of a single country. The number of P. ramorum susceptible plant species and the number of countries involved in their trade have certainly facilitated spread and pose a formidable challenge to the current effort to eradicate or contain the pathogen.

Keywords: Horticultural trade, landscape pathology, networks epidemiology

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Citation

Pautasso, Marco; Harwood, Tom; Shaw, Mike; Xu, Xiangming; Jeger, Mike   2008.  Epidemiological modeling of Phytophthora ramorum: network properties of susceptible plant genera movements in the nursery sector of England and Wales.   In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 257-264.