Fight back against ash dieback under way

While John Spink admits the current position of our native ash remains “grim”, he is determined to remain optimistic that stocks can recover in the future. John is the head of the Teagasc Crops, Environment, and Land Use Programme, and is working alongside not just his Irish colleagues, but international experts in trying to chart a way out of the dieback morass.

Optimism is hard to maintain however at this time of year when the full extent of the dieback problem is at its most glaring.

“At this stage it’s probably everywhere,” says John of the fungal pathogen Hymenoscyphus fraxineus responsible for ash dieback.

"I drive around the country and you see dead and dying ash trees all over the country. I don’t think there’s anywhere that’s escaped it, and even if there are some very very isolated trees that have escaped, I’m sure they will eventually spread.

“The literature says the spores can travel up to 35km. It would have to be a very isolated ash tree to avoid that.”

Ironically it’s that working assumption that every mature ash tree has been exposed to the fungal spores that is the source of the Teagasc optimism.

“There’s going to be a very small percentage of the current ash trees that live - it’s what we expect,” says John.

Healthy

While the percentage of trees which may be resistant currently remains unknown, John outlines, “certainly people are estimating it’s less than one per cent”.

“A lot of the work done currently is to identify trees that are healthy and surrounded by otherwise unhealthy trees, and to then try to propagate those and to test them and see if they really are resistant. Because obviously the last thing you want to do is think that you have found some resistant trees and to start planting them up again, only to find in a few years’ time they are not as resistant as you thought, and have them die again.”

Teagasc staff have thus found some apparently healthy trees within their own stands containing lots of different varieties and strains of ash, and which are otherwise full of ash dieback.

“If people have very healthy ash trees they should keep an eye on them - certainly don’t cut them down, because they may have the odd resistant one,” says John, recommending they inform Teagasc’s forestry department.

Using cuttings carefully removed from the seemingly healthy ash, Teagasc, and their Swedish counterparts Skogforsk recently hosted a two-day workshop on methods of propagating ash for future restoration,appropriately enough it was held at the Ashtown Research Centre.

Representatives of both academia and industry from seven European countries attended and participated in the important workshop. It also included visits to the two Ash gene-banks established at the Teagasc Oak Park Research Centre in Carlow, and the Phoenix Park, Dublin.

The genetic make-up appears to hold the secret to some of these dieback resistant ash trees.

“They have something in their DNA that means that the disease either can’t infect them, or if it does infect them, it doesn’t multiply and prosper, but I don’t think anyone knows what the mechanisms is yet. That’s some of the work that’s going on,” says John.

Occasional resistance to the disease is not an Irish phenomenon.

“Dieback is a relatively new in Ireland but it has come over from Eastern Europe, so they have been working on it much longer over there, and they have some lines which are still surviving, so we have some material that has come in from elsewhere in Europe that appears to be resistant there.”

Elms

The concepts applied to help restore our ash population is significant for another native tree - Wych elm (Ulmus glabra) – which was similarly decimated by Dutch elm disease. First detected in Europe in 1967 the disease swept across the continent in the 1970s. By 1990, most elm trees in Europe were dead.

“I think people would be surprised that we still have some elms in the country despite the Dutch elm disease,” he emphasises.

“They’ve only just realised that in the UK as well. So they have started collecting samples of those elm trees that are still alive and hopefully, if they are resistant, they are going to start propagating them and start re-establishing elms. I expect the same thing will happen with ash.”

Dheeraj Rathore, Teagasc Tree Improvement Researcher, is commencing the newly established elm project in Ireland.

Returning to ash, John is measured when it comes to assessing the hope for the species.

“We have to be optimistic. If we thought it was a hopeless case we wouldn’t put all the effort in, so we do believe that we can find multiply ash that will eventually survive despite dieback – how long it will take us, I couldn’t say.”

He said if they did find a strain of ash they had confidence in, they would remain cautious.

“We would be quite cautious about multiplying it up and encouraging people to plant it unless we were assured it was resistant – and it would still be resistant in 20 and 30 years time.”