A couple of days ago I visited a friend in Norwich who has an Ash tree in his garden. He was concerned that it might have Chalara Ash Dieback disease. Fortunately, after we’d had a look, we realised his fears were unfounded.

When I wrote about Ash trees in July 2012 Ash Dieback disease (caused by the fungus Chalara fraxinea) had already been found in Britain in a tree nursery in Buckinghamshire, but it wasn’t until October 2012 that the first cases were confirmed in East Anglia (reference). It was a shock to hear that the disease had been discovered not far from Norwich in Ashwellthorpe Lower Wood, a lovely Norfolk Wildlife Trust reserve that I have visited on several occasions.

I have looked at  number of Ash trees in Norwich, for example in Earlham Cemetery, but I still haven’t seen the symptoms of the disease first hand. But a lot of information is available on the internet. I started with the Woodland Trust’s page “How to identify ash dieback“.

The page led me to some Forestry Commission videos, which are clear and easy to follow. They are on YouTube and I have embedded them below. (The first two are also embedded in the Woodland Trust’s web page.)

How to identify Chalara ash dieback in the field:

Chalara ash dieback – identifying symptoms in the winter:

Chalara dieback of ash – Spring symptoms:

Chalara Ash Dieback has now been found in many parts of the UK (see map).

If you discover an outbreak of the disease, you can use the Forestry Commision’s tree alert form to report it. Photographs are very useful and priority is given to reports which include pictures. There is also a Tree Alert App, which you can use if you have a smartphone.

Chalara fraxinea has caused the loss of ash trees in a number of European countries, including between 60 and 90 per cent of Denmark’s ash trees. The worry is that the effect will be devastating in Britain too. Hopefully the genetic diversity of our ash trees may mean that there are naturally resistant trees already growing in our countryside.

In Britain, there appear to be two sources of infection. In East Anglia and along the east coast wind-borne fungal spores have brought the disease to Britain from continental Europe. Further west, trees have been planted with infected stock imported from continental Europe (reference). Regulations were introduced to control the import of infected trees in late October 2012 (reference), but only once many infected newly-planted trees had already been discovered.

The Forestry Commission have issued advice to forest visitors, which should be followed to limit the spread of the disease. However, they advise that the risk of visitors spreading the disease is very small and they have not suggested that woods or forests should be closed to visitors.

Chalara Ash Dieback affects other species of ash as well, including Fraxinus angustifolia, F. ornus, F. nigra, F. pennsylvanica, F. americana and F. mandschurica. The least susceptible species are reported to be F. americana and F. mandschurica (reference).