Abstract
Phytophthora ramorum and Phytophthora kernoviae are exotic plant pathogens first found in the UK in 2002 and 2003, respectively. Both pathogens have the ability to kill trees and native heathland species in the UK and cause serious disease on a wide range of garden shrubs found within heritage gardens and the hardy ornamental industry. In England and Wales, there have been over 250 outbreaks of P. ramorum or P. kernoviae outside of nurseries (many in heritage gardens or parks), of which about a quarter have been eradicated so far. From April 2009, Defra have funded an intensive disease management programme to manage the risks from these pathogens, through an eradication programme and increased public awareness, as well as a continued programme of research. This project will complement previous and ongoing research with the overall aim to develop strategies for managing Phytophthora ramorum and P. kernoviae, in order to prevent further pathogen and disease impacts in heritage / historic gardens and parks. The three-year project will be led by ADAS in collaboration with the Food and Environment Research Agency (Fera), the Royal Horticultural Society (RHS) and the National Trust (NT). The specific objectives of the research are to: 1. Develop appropriate chemical, non-chemical or cultural control methods for disease management 2. Undertake epidemiological studies to guide development of eradication, containment and management plans 3. Develop strategies to enable sustainable replanting after clearance in affected gardens. Research under Objective 1 will look at integrated approaches for management of Phytophthora ramorum (Pr) and Phytophthora kernoviae (Pk) at heritage garden and park locations under a range of scenarios. These scenarios will include the potential for management of disease on valuable tree or under-storey specimens that are infected with Pr or Pk, protection of susceptible hosts from infection, and reduction of disease pressure in soil and leaf litter where infected specimens have been recently treated or removed. Fungicides will be considered as a component of integrated strategies for Pr and Pk control, with potential active ingredients identified from laboratory studies in this and previous work. Fungicides programmes will be developed that minimise the risk of developing pathogen resistance to specific active ingredients. Optimum timing of fungicide applications will be determined based on knowledge of host plant susceptibility at different times of year (from Objective 2). Strategies will be developed to manage disease on valuable specimen / heritage plants where complete removal from the garden is undesirable. Techniques to be evaluated include the use of micro-injection technology to treat infected tree specimens, and the use of pruning together with fungicide applications (to foliage or around the stump base) to protect susceptible plant re-growth. Chemical and non-chemical treatments will be tested for their effects on Pr and Pk surviving in soil and leaf litter, while mulches will be used to determine whether disease spread can be reduced. Under Objective 2, research will provide increased knowledge of Pr and Pk in order to better target management strategies. Laboratory studies will investigate the infection process for the two pathogens in a number of important plant genera (rhododendron, magnolia, viburnum, camellia and pieris) commonly found in managed garden situations. Monitoring of susceptible plants at outbreak sites will provide information on the susceptibility of key host plants at different times of year, to determine potential optimum timings for fungicide sprays. Finally, the most effective treatment methodologies developed within the first two years of the project will be used in a selected garden/park outbreak of Pr or Pk as a case-study to demonstrate and validate their effectiveness in reducing disease pressure and re-infection at the site. Within Objective 3, the project team will conduct a desk study to produce an inventory of plant genera and species which are present in gardens/parks infected with Pr and Pk, which have remained uninfected by the pathogens despite being exposed to significant inoculum levels. The desk study will identify varieties, species and genera which are important in terms of their use in gardens and parks (e.g. for windbreaks and underplanting specimen trees), for which there is no previous evidence of susceptibility to Pr and Pk. Subsequent infection studies in a laboratory will be done to confirm whether identified species show tolerance to Pr and Pk, and therefore have potential as species for replanting in situations of high disease pressure. This research project will directly support the Defra Phytophthora Disease Management Programme for P. ramorum and P. kernoviae in England and Wales, addressing the key policy objectives. Project outputs will be relevant to independent stakeholders, landowners and garden end-users, facilitating disease management. Core outputs from the work will be regular dissemination in appropriate format to stakeholders, including recommendations and practical guides for disease management and eradication action at outbreak sites of P. ramorum and P. kernoviae in the natural and semi-natural environment.
United Kingdom