Ash Dieback (Chalara fraxinea)

Report from Ash Dieback seminar run by the Forestry Commission in Stirling on 26 Mar 2013


Here are some of the main points from the meeting:

It seems inevitable that every Ash tree in Scotland will become infected with the disease.

The disease will kill most of the trees. It will typically take a tree some years to die completely.

A small percentage of Ash trees are expected to be genetically resistant to the disease. This could be 1 or 2 %, or possibly up to 5 %. Such trees will be infected but will not die, according to the current state of knowledge. (but the disease is so new that much about it is speculative at present)

Eventually, over the long term (not in our lifetimes), the Ash population in Scotland will hopefully recover to something like its present extent, due to reproduction by the resistant strains of the trees. (which can possibly be aided by planting seedlings from resistant trees once the resistant strains have been identified)

If recently planted Ash are found to be infected, the whole planting should be destroyed. Inform the FC and get further advice from them.

Mature Ash trees that become infected should not normally be cut down (unless they cause danger to the public). All Ash trees will eventually become infected, so if the policy was to cut them down then Ash would be wiped out in Scotland. But if they are left, the resistant trees will survive and the regeneration can start from those.

Many insects and other life forms are dependent on Ash. If Ash disappears, they will too. But if infected Ashes are spared then these life forms can cling on to existence via the few resistant Ash trees, and then repopulate the country when the Ash does.

In the case of mature Ash trees, the disease overwinters in the leaf litter beneath the tree. If you have a favourite Ash tree that you want to protect, for instance in your garden, you should get rid of the leaf litter each winter. The way to do this is to burn it near where you found it. Do not move it somewhere else and dump it there! - you would just be spreading the disease.

All infection should be reported to the FC. They will then advise on appropriate action.

To avoid spreading disease, do not move any material from Ash trees from one place to another. After visiting a site with Ash, make sure there are no bits of dead leaves stuck to your boots. Mud is ok. The fungus is only found on tree material. So long as this is kept in mind, there is no need to stay away from Ash trees to avoid spreading the disease; it is much better if people do visit trees to look for the disease and report it.

The disease is difficult to recognise, as many other factors can cause similar symptoms. For anyone interested there is plenty of material online, and I have some leaflets which will be available at LNHG events. It is easiest to recognise in summer and I anticipate having a Chalara walk this summer where we can learn what to look for and see how we get on (for once we'll be hoping NOT to find our target species!)

Ash in NW Scotland, which includes our area, is being treated as a high priority by the FC. This is partly because in this region it has many important associated organisms, such as Oceanic lichens, and because the disease may behave differently in the unique west coast climate, and we could get lucky and find it doesn't do so well there. Also there is more genetic diversity here where most Ash is native rather than planted, so more chance of finding resistant strains.

I have a lot more information I can give to anyone interested, and there is a lot available online (Google "Ash Dieback"). http://www.forestry.gov.uk/pdf/WorrellReport-ChalaraImpacts.pdf/$file/WorrellReport-ChalaraImpacts.pdf gives a lot of background. http://www.forestry.gov.uk/chalara#Symptoms has good descriptions of the symptoms. The state of knowledge is changing very rapidly and anything you read on the web may be out of date even if it looks recent. The benefit of yesterday's meeting was to hear the top people involved give the very latest info.

The LNHG will do its best to monitor the situation and keep people informed.  Everyone who lives locally is in a position to help and the LNHG will be happy to co-ordinate efforts.

Updates will be posted on the LORN site and the LNHG website.

Carl Farmer
27 Mar 2013

 



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