By Jane Hargreaves

Ash dieback, also known as Chalara, is a disease of ash trees which arrived in England from Europe in 2012 and is spreading rapidly. It is already found in more than half the country and has been observed in Lower Grass Wood. To encourage awareness of ash dieback all English parishes have been invited to apply for tags to place on a few trees to help monitor and highlight the progress of the disease. The spread is by windblown spores of the fungus Hymenoscyphus fraxineus and is about 10 miles per year.

Upper Wharfedale and Littondale have some of the most precious native ash woodlands in the country with their unique fauna and flora. The  loss of this habitat will fundamentally change our dales. The disease causes lesions on the trunk, bark and branches. The lesions tend to be centred round a small shoot which has died. The top of the tree may have died first while the lower branches still seem to remain normal. The spores enter the leaves on the crown of the tree and show discolouration and the leaf stalk may be brown. Good pictures of dieback can be seen at

British trees seem to show better resistance than those across much of Europe where up to 90% have died. The Government-funded Living Ash Project is trying to identify trees which show greatest resistance to the disease. A new danger to ash trees is likely to arrive in the form of a beetle, the emerald ash borer. Sadly, the trees most resistant to ash dieback appear to be most susceptible to damage by this beetle. Old ash trees may survive for some time, continuing to give protection to plants and wildlife, although they will finally succumb to other diseases when weakened. Large scale tree planting by the National Trust has seen more than 100 000 trees planted in the last two years on the Malham Tarn Estate and the Yockenthwaite Estate. Already Parish Wildlife Projects have encouraged local communities to plant native trees on Parish land and on land offered by local farmers and other land owners. Perhaps then there will be more woodland to receive the hoped for resistant ash trees of the future. There is no cure for ash dieback but genome research may give cautious optimism that we will have some ash trees remaining in generations to come.