Epidemiological modelling of Phytophthora ramorum incidence and spread in the UK

Tom Harwood, Marco Pautasso*, Xiangming Xu, Mike W. Shaw & Mike J. Jeger*

*Division of Biology, Imperial College London, Silwood Park Campus, SL5 7PY, UK

International Congress of Plant Pathology nr 10, Torino (Italy) August 2008

Phytophthora ramorum in England & Wales (2003-2006)

Outbreak maps courtesy of David Slawson, PHSI, DEFRA, UK

Climatic match courtesy of Richard Baker, CSL, UK

511 nurseries/ garden centres

85

426

168 historic gardens/ woodlands

46

122

g 11 v

alue

s

0

1

2

3

4

5

0

1

2

3

4

5

Distance (km)0 20 40 60 80 100

g 11 v

alue

s

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a: Garden/Nursery 2003 b: Garden/Nursery 2004

c: Garden/Nursery 2005

Distance (km)0 20 40 60 80 100

g11

valu

es

0

4

8

12d: Garden/Nursery 2006

Spatial analysis – aggregation of nurseries & garden centres

SimulationsLog (total numbers of infected plants after 10 years)

Source of variation df MS VR P

Between locations 9 1774 694 <0.001

Allowing for differences between locations

R 1 18270 7147 <0.001commerce 1 2087 817 <0.001inspections 1 49 19 <0.001R.commerce 1 126 49 <0.001

Other interactions very small and non-significant

Residual 3983 2.56

Lower epidemic threshold for two-way scale-free networks (unless networks are sparsely connected)

N replicates = 100; error bars are St. Dev.; different letters show sign. different means

at p < 0.05

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