Researchers are working towards developing a cost effective solution to controlling Ash Dieback fungal disease, a major threat to 80 million ash trees in the UK. As part of the plan to tackle Ash Dieback and other invasive pests and diseases, the government has formulated a team of ten internationally recognised experts in plant health, forestry and wider related disciplines as part of the Tree Health and Plant Biosecurity Taskforce. The taskforce includes three entomologists, Professor Charles Godfray from Oxford University, Professor Simon Leather from Harper Adams University College and Professor John Mumford from Imperial College as well as a number of social and environmental scientists.
Ash Dieback, caused by the Ascomycete fungus Chalara fraxinea, was first recorded in the 1990s in Poland, after which it spread to other countries in continental Europe. Chalara fraxinea is the asexual stage of the fungus, the sexual stage being Hymenoscyphus pseudoalbidus, which to date has only been found in continental Europe. The fungal spores are dispersed by the wind, after which they land on ash leaves and germinate, leaving small necrotic spots. These can then extend into the main stem of the tree, killing plant tissue and leaving behind a diamond shaped lesion which begins to girdle the sapling, preventing nutrients being effectively transported around the plant. The tree will eventually be completely girdled and die, with secondary infections by fungal pathogens such as honey fungus often establishing at the same time to weaken and kill the tree.
In February 2012 Chalara fraxinea was detected in a shipment of ash saplings sent from a nursery in the Netherlands to Buckinghamshire, UK. Since then, the fungus has been found in a number of locations in England and Scotland, with a further four cases confirmed in the nursery trade relating to plant materials imported from the Netherlands and Germany. In October 2012, Fera scientists confirmed a small number of cases in East Anglia in ash trees which did not appear to have any associations with recently supplied nursery stock. Chalara fraxinea is estimated to have affected 100,000 saplings and mature trees in the UK in a matter of weeks, and is consequently being treated as a quarantine pest under national emergency measures, with hundreds of staff members from government agencies and plant health experts undertaking surveys across thousands of UK sites where the fungus has been found to be present.
A commercial environmental company Natural Ecology Mitigation, is working in collaboration with Forest Research, International Pesticide Application Research Consortium (IPARC) and Imperial College researchers in order to formulate techniques to manage the fungus. The consortium is now awaiting approval from the government and investors to carry out further tests of a product called CuPC33, which has been proposed as an effective copper sulphate based chemical control method to combat the fungus. To date laboratory trails have shown that CuPC33 is highly effective at controlling fungi when applied by spraying or by trunk injection, and is also effective at controlling other serious fungal pathogens of UK trees such as Bleeding Canker of Horse Chestnut, caused by the bacterium Pseudomonas syringae, and Sudden Oak Death, a disease of oak and larch trees caused by the pathogen Phytophthora ramorum. Furthermore, research suggests that CuPC33 could be applied to woodlands using low volume spray technology which would allow 10 litres of diluted CuPC33 to treat 1 hectare of land, making the process efficient in terms of cost and resources. Professor Simon Leather, Professor of Entomology at Harper Adams University College, explained the next step in tackling Ash Dieback:
“ We hope to be able to develop a number of ways to apply CuPC33 that will be appropriate to different types of fungal and bacterial diseases and different species of tree. The next step for us is to test this solution on infected trees in the field. We expect these trials to begin next Spring.”