This morning several newly discovered cases of Chalara fraxinia, the ash dieback fungal disease, have been announced in Scotland, including near Eyemouth in the Scottish Borders and near Castle Douglas in Dumfries and Galloway. This is bad news indeed. The ash, Fraxinus excelsior, is the third most common native broadleaved tree in British woodlands: it provides 5% of our native forest cover and contributes massively to both the beauty and diversity of our landscape and our timber supply, being the best tree for producing quality firewood and is also the source of high quality timber for the making of many products.
Perhaps the most disastrous consequence of this disease, however, is the impact on associated plants, animals and insects. Over 100 insect species are associated with Ash and 27 of these are known to be totally dependent on it. In turn, the Ash-related ecosystem supports deep-shade-intolerant woodland plants like our iconic bluebells and primroses, plus other rare species like Enchanter’s Nightshade, the White Letter Hairstreak butterfly, the White Admiral butterfly, Greater and Lesser Horseshoe bats and the Dormouse.
From the number of cases now being reported, it seems we’re rapidly reaching a stage in the UK where containment may not be an option. Whatever we do, a high percentage of our native ash trees look set to disappear from our countryside and gardens. In Denmark, between 60 and 90% of ash trees have been destroyed by Chalara, so this is a very serious threat.
Unquestionably the source of many infected trees is from imports from abroad. Councils, among others, have sought the cheapest available trees for mass planting and sadly have bypassed UK-grown trees in favour of cheap ash saplings from abroad. Poor planting practices and woodland management, again often a result of cost cutting, have meant trees being planted too close together or not being properly weeded and managed, allowing disease to spread.
Officials were first warned about ash dieback by Scandinavian scientists at a conference in 2007, after which the Forestry Commission’s Head of Plant Health sent an alert to Defra, which was ignored. In fact, instead of heeding this warning, ministers instead cut back on funding for biosecurrity and research: Between 2004 and 2010 the monitoring and biosecurity budget was reduced by almost 60%.
Is there a solution to Ash Dieback for the UK?
Experts are already questioning the wisdom of the so-called ‘slash and burn solution’, since there’s a danger of taking out resistant strains as well. (One can’t help thinking, with a shudder, of parallels with the Foot and Mouth 100% cull policy, now so widely questioned.) Whilst young ash saplings in infected nurseries will all have to be destroyed, as will young trees in all infected areas, since they are most susceptible, for mature trees the policy of destruction could be precisely the wrong way to go.
Swedish scientists, who have been studying the fungus for more than a decade, say such a policy of destruction could well be counterproductive. If we want native ash to continue to thrive, we should look closely at what has happened in places like Sweden, where only a third of ash trees have died over the past decade. Apparently some are able to find an “equilibrium” with the fungus and although infected, are able to overcome it and thrive. Such strains could hold the key to protecting ash by breeding their genotypes into saplings.
There are also fungicides which are known to be effective against other fungal tree diseases and researchers are saying that it’s a fair bet that some of these will be effective against ash dieback. However, they would need to be trialled and registered before they could be used to treat Chalara-infected ash trees. Such process are generally lengthy, due to bureaucracy and funding issues. Isn’t it time the government restored a little of our faith by fast-tracking such research and development in order to try and save our ash trees?