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Mitigation of impacts of on ash dieback in the UK – an investigation of the epidemiology and pathogenicity of Hymenoscyphus pseudoalbidus (anamorph: Chalara fraxinea) and development of methods for detection and containment of disease spread - TH0119

Ash dieback, caused by the fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), was first recorded in Poland in the 1990s and has since spread widely across Europe causing leaf loss and crown dieback symptoms which can lead to tree death in a range of Fraxinus species including the common ash (the third most common tree in the UK). In early 2012 the disease was found in the UK on a nursery in Buckinghamshire and subsequently on further nurseries and in recently planted ash trees at a range of locations. In October, the disease was found causing outbreaks in the wider environment including in areas of established woodland which did not appear associated with recently planted ash. Observations indicate that the pathogen had been present in the UK environment for several years prior to its detection, and that it is no longer possible for ash dieback to be eradicated. However, as part of the Chalara Disease Management Plan developed by Defra, a number of research priorities have been identified which will assist policy makers in reducing the impact of this disease in the UK and in implementing a long-term strategy to support recovery of the UK woodland environment. A Pest Risk Assessment (Forestry Commission, 2013) has also been published which outlines knowledge gaps and priorities for research. This research proposal will address the key research priorities identified in these documents in order to support government policy objectives to reduce the rate of disease spread. Research on the epidemiology of H. pseudodalbidus, including the specific conditions required for infection, sporulation and survival of the pathogen, will identify the relative risks posed by the pathogen to the UK compared to other countries in Europe and will provide core data for modelling of pathogen spread. H. pseudoalbidus is spread by aerially dispersed spores (ascospores), released from fruit bodies (apothecia) which are produced between June and October, mainly on fallen rachises in the leaf litter from the previous year. Monitoring in Europe has shown that spores are released in the early morning and modelling in the UK suggests that distances of dispersal may be in excess of 30 miles. This project will identify the durations of spore release in UK outbreaks both in terms of time of day and duration of release during the spring/summer and also measure the volumes of spores being released into the air. The question of the frequency and volume of spores being dispersed over long distances, particularly from sources outside GB will also be investigated. Experiments in the laboratory and in natural outbreaks will examine the susceptibility of ash species commonly grown in the UK and determine how seasonal factors and inoculum levels affect infection. This will serve to develop reliable protocols to support research into finding sources of resistance to ash dieback being undertaken by the BBSRC/Defra funded Nornex project. Early diagnosis of an infected plant is very important to successful surveillance and this project will collaborate with Nornex to develop a Lateral Flow Device (LFD) for disease confirmation and use specialist genomics to explore sources and pathways of pathogen spread. The project will also develop methodologies to assist in containment of disease spread, focussing on management of infected waste and chemical treatments for protection of young trees or valuable specimens. Research will determine if processes such as composting are effective in eradicating the pathogen from infected plant material and fungicides will be evaluated for use as protectant treatments as either foliar sprays or tree injection treatments for young ash or valuable specimen and heritage trees respectively. Successful treatments will be integrated into good practice guidelines for disease management.
See project description
Project Documents
• IR - Interim Report : Short report on results from fungicide efficacy testing for chalara v2   (212k)
Time-Scale and Cost
From: 2013

To: 2016

Cost: £657,848
Contractor / Funded Organisations
F E R A (FERA), Forest Research Agency
Plant health