Ash dieback is caused by the Chalara fraxinea fungus. The fungus attacks the growth of leaves, particularly at the tree's crown,and can be fatal.
90% of all Ash trees in Denmark have been killed by the fungus in seven years, and the disease is spreading through Central Europe.
Scientists are yet to find out how the disease spreads, but experts think it it could be by insects or rain splash.
Over longer distances it is believed to be transferred by the movement of infected tree; hence today's ban on imports.
Symptoms of Chalara fraxinea include:
- In severe cases, the entire crown shows leaf loss and dieback
- There may be the formation of dormant shoots under the bark on branches and the trunk
- Foliage Leaves can suffer from wilting and black-brownish discoloration