This document summarizes a study on Phytophthora findings in UK nurseries and how they relate to management practices. Over 1700 samples were collected from 15 nurseries and tested for Phytophthora. Preliminary results found differences in incidence rates between nurseries that could be linked to differences in practices. More positive findings came from plant root samples than other sample types like water. Observations made during sampling highlighted potential areas for improved biosecurity and water management to minimize Phytophthora spread, such as improving drainage, avoiding mud and puddles, and carefully managing water sources. Next steps include further lab testing, reporting findings to nurseries, identifying species through metabarcoding, and interpreting results in relation

1. Phytophthora findings in UK
nurseries and links to
management practice
Phyto-threats workshop – 04 Oct 2017
David Cooke, Leighton Pritchard, Peter Thorpe, Eva Randall & Beatrix Clark
Ana Perez, Sarah Green, Debbie Frederickson Matika - Forest Research
Tim Pettit - University of Worcester
Bethan Purse - CEH
Jane Barbrook - APHA
Alexandra Schlenzig - SASA
Thanks to all nurseries for allowing access

2. Invasive potential – high
& trade related

3. Dave Rizzo Youtube.com
California Oak Mortality Task Force
Phytophthora dissemination
• Sporangia – air, water, splash
• Zoospores – water
• Oospores and chlamydospores – persistent resting stage
>160 species of Phytophthora

4. Objectives
• Using metabarcoding to analyse community
structure in nurseries and associated ecosystems
– Providing insight into Phytophthora findings to improve disease
management and advise ‘best practice’
• Phytophthora community modelling
– Explain variation in Phytophthora diversity among nurseries –
trade, management and ecology
Minimising risk by supporting nursery trade

5. Methods
• Questionnaire – simple data on nursery practices
• Sampling
– Fine-scale – testing nurseries by project staff for detailed
breakdown of management problems and solutions
– Broad-scale – sampling wider nursery selection alongside statutory
plant health testing
– OPAL – engagement with community sampling
• Phytophthora detection and metabarcoding
• Computational biology to process sequence data
• Interpretation and provision of feedback to owners
• Use of data for Community modelling

6. Field
Capture
spores on
filter
Sequence DNA
barcode
Computational
biology
Validation of
species
in sample
Results to
nurseries &
project team
Roots
Lab Computer
Phytophthora-
specific DNA
amplification

7. Sampling – practical issues
• Control points/contamination
hazards (Parke et al 2012 Plant Disease)
• Roots of a selection of hosts
• Water flowing through pots
• Symptomatic & asymptomatic
• Water supply

8. Fine-scale sampling
• 34 sample sets from 15 nurseries (6 English, 1 Welsh, 8 Scottish)
• 1700 samples plus associated meta-data
• >400 PCR tested for Phytophthora
– Plant roots (93) range of 35 hosts
– Water filters (132)
– Buffer associated with filter (170)
• Washed through plants
• Borehole
• Ponds/ditches
• Equipment washing (e.g. trolleys)
• Water blanks
• Isolations on some samples
– 3 confirmed P. austrocedri findings
– P. cambivora on shelter belt trees

9. Phytophthora findings by nursery
• Preliminary results suggest differences in practice influence
Phytophthora incidence
• Ten nurseries ordered by incidence data

10. Phytophthora findings by sample type
• More positive findings from roots
• Blank controls and irrigation water included water tests

11. Broad-scale sampling
• Linked to statutory testing (PMU and APHA)
– Target 50 nurseries/garden centres England & Wales
and 25 in Scotland sampled in 2017 and 2018
• 27 sets of root samples provided
– 11 from Scotland
– 16 from England and Wales

12. OPAL
• Community sampling/
engagement with help of
David Slawson
• Areas of recent planting
• 10 samples provided
• Indication of Phytophthora
species in ‘natural’
environments

13. Observations while sampling
• Material coming onto site
o Water source – borehole/mains water, streams or lakes used
in some cases (caution needed on any disease upstream)
o Compost – not testing but no current concerns
o Planting material – highest risk, native seed, cuttings, trade
from EU or third countries. Quarantine new plant material
o Visitors/staff/vehicles – Biosecurity implementation varies.
Isolated hard standing for all delivery and dispatch to limit
traffic. Mud a problem in some nurseries. Footbaths and
vehicle washing serves to increase awareness.

14. Observations while sampling
• Dissemination on site
o Plant-to-plant spread – depends on growing system
o Puddles commonly positive – improve drainage
o Mud spreads inoculum around site
o Infection in shelter belt trees
o ‘hospital / recovery’ areas in some nurseries generally not a
good idea. Rapid disposal optimal

22. Good water management

23. Good water management

24. Improve drainage - avoid mud/puddles

26. Next steps
• Accelerate lab testing to process sample backlog
• Report Phytophthora findings to nurseries
• Run metabarcoding to identify species present
• Test and validate new computational biology
platform
• Report specific species finding to nurseries
• Data interpretation in relation to management