Ash Die Back, Chalara (Hymenoscyphus fraxineus)

Ash dieback will kill up to 95% of ash trees across the UK. At a cost of billions, the effects will be staggering. It will change the landscape forever and threaten many species which rely on ash.

What does ash dieback look like?

Ash dieback can affect ash trees of all ages. Younger trees succumb to the disease quicker but in general, all affected trees will have these symptoms:

.Leaves develop dark patches in the summer.

They then wilt and discolour to black. Leaves might shed early.

.Dieback of the shoots and leaves is visible in the summer.

.Lesions develop where branches meet the trunk. These are often diamond-shaped and dark brown.

.Inner bark looks brownish-grey under the lesions.

.New growth from previously dormant buds further down the trunk. This is known as epicormic growth and is a common response to stress in trees.

What happens to the tree?

The fungus overwinters in leaf litter on the ground, particularly on ash leaf stalks. It produces small white fruiting bodies between July and October which release spores into the surrounding atmosphere.

These spores can blow tens of miles away. They land on leaves, stick to and then penetrate into the leaf and beyond. The fungus then grows inside the tree, eventually blocking its water transport systems, causing it to die. The tree can fight back, but year-on-year infections will eventually kill it.

How you can help

.Clean your shoes before and after visiting a wood.

.Avoid taking cuttings or plant material from the countryside.

.Wash your car or bike wheels to remove mud or plant matter.

What impact will ash dieback have?

It’s thought that we are going to lose up to 95% of our ash trees in the UK. This is going to have a devastating impact on the landscape and the biodiversity of our woodlands, as well as a major loss in connections between habitats as we lose hedges and individual trees outside of woods. The predicted cost of managing the diseases is high. It includes the practical expense of clearing up dead and dying trees, to the loss of its environmental services such as air purification.