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Epidemiology of natural outbreaks of Phytophthora ramorum - PH0195

To investigate the epidemiology of natural outbreaks of Phytophthora ramorum under UK conditions

Policy relevance: P. ramorum is the subject of EC emergency legislation due its potential threat to European tree species and forest ecosystems. The measures are aimed at preventing the spread of European isolates and the introduction of non-European isolates. In the USA it is causing extensive oak mortality (Lithocarpus, Quercus) along the Californian coast. In the UK and Europe, outbreaks of P. ramorum have been restricted to certain ornamental plant species (including Rhododendron, Viburnum, Pieris, Camellia, Kalmia) in nurseries and a few public gardens. In early November 2003, the disease was confirmed in a Southern Red Oak (Quercus falcata) within one of these managed gardens in SE England and the Netherlands reported a finding on Quercus rubra. Active eradication and containment measures are being applied and future strategy is under consideration. The risk to UK and European tree species from P. ramorum, especially those in the Fagaceae, is still unknown. The epidemiology of P. ramorum is being investigated under a number of Defra projects using in vitro and limited in vivo methodologies. This work is providing key data on the environmental conditions required for sporulation, dispersal and survival of the fungus, and is investigating host susceptibility and the potential for establishment of latent infections. However in order to fully understand the biology of this disease and quantify the risks to native trees and ornamental plant species, it is essential to investigate the epidemiology of the pathogen under natural UK conditions on established hosts. Issues such as the current inoculum levels at infected sites and whether these levels are below a critical threshold can only be investigated through monitoring of such natural outbreaks.

ADAS will be responsible for carrying out experimental work on sites in the southwest and will be paid separately and will be funded form a separate source.

Intended use of results: Results will support the development of pest risk analyses and pest risk management strategies, and to assist the progress of plant health policy and contingency planning for P. ramorum. The results will compliment the current work on comparative behaviour, mating types, host susceptibility, epidemiology and control at FRA and CSL (PH0192, PH0193S, PH0194, HNS 123) and with future work on the RAPRA EU project due to start in January 2004.
Main objective: To investigate the epidemiology of natural outbreaks of Phytophthora ramorum under UK conditions

Scientific objectives (as revised 20 April 2005):
1. Monitor disease symptom and outbreak development at infected sites, including the potential for latency.
2. Determine the mechanisms of spread of P. ramorum under UK conditions
3. Quantify the inoculum potential at selected sites and investigate the mechanisms and longevity of spore survival.
4. Determine whether eradication activity impacts on inoculum and disease development
5. Ensure that all results and observations are effectively and appropriately communicated within CSL, PHD, PHSI, FC and FR.

Project Documents
• Final Report : Plant Health Final Report: Epidemiology of natural outbreaks of Phytophthora ramorum   (1283k)
Time-Scale and Cost
From: 2003

To: 2006

Cost: £170,498
Contractor / Funded Organisations
Central Science Laboratory
Alien Species              
Environmental monitoring              
Plant health              
Plant Pests and Diseases              
Plants and Animals              
Fields of Study
Plant Health