Friday, November 16, 2012

Ash dieback in Poland and Japan

Two very interesting articles have been published recently on ash dieback disease (Chalara fraxinea).

One, in the Telegraph, is by Cole Moreton  who went to the forest area in Zabodny, Poland, where the disease was first noted in Europe in 1992:

It paints a very gloomy picture of the prospects for ash trees in the UK.  One of their forest managers was asked about prospects here:

“Has it been seen in the older trees?” It has. This experienced man of the forests puts his hand on his heart. “Then I am afraid it is over for you. It is too late. The game is over.”  However, the Poles pointed out that 15 to 20% of trees survive and seed from these might carry the immunity to future generations.

While this may seem to be a good thing, the warning from the Botanical Society of the British Isles (BSBI) should be heeded: "Woodland plantations and hedgerows made of cloned stock or non-native trees are going to be even more prone to failure than most food crops, as they are so long-lived."  In other words it is important to maintain genetic diversity and not take all future ash trees from one or two genetically identical, or very similar, clones."  The BSBI also say, rather more encouragingly: "Ash dieback, like other diseases of wild plants, is simply part of the ecosystem, and its main effect is likely to be to increase diversity and ultimately the stability of woods. Even if it were possible, there would be no point in trying to isolate British plants from worldwide diseases, because that would make them more vulnerable to serious plagues in future."

The whole article is here:

Their assertion though that "ash dieback is not known to kill mature trees" does not seem to be correct in the light of experience from Poland and elsewhere.

Another enlightening web site is TreeBASE (a database of phylogenetic knowledge) which almost certainly explains various reports that ash dieback came from Asia or China.  In fact the fungus seems to be present in Japan on Manchurian ash (Fraxinus mandshurica) a species found in China, Korea and south east Russia as well as Japan.  TreeBASE say: "Hymenoscyphus pseudoalbidus is the causal agent of ash (Fraxinus excelsior) dieback in Europe. It was recently separated from the European H. albidus based on molecular analyses, while morphologically scarcely distinguishable. Hymenoscyphus albidus was reported under the nomenclatural synonym Lambertella albida on petioles of Fraxinus mandshurica in Japan."  It then gives some rather more complicated details.

On the assumption that the fungus was present in Japan before Europe, Manchurian ash may, of course, be rather more resistant to the disease than European ash, but much more work needs to be done to establish the evolutionary pathways and possible dispersion routes of spores of both the European and Far Eastern strains of Chalara fraxinea, although such knowledge may not enable anyone to stop its advance, it could help with mitigation strategies.

Work on Chalara fraxinea seems to have been done by scientists in Japan, Poland, Denmark, Belgium, Switzerland, UK and probably many other places.  What I find rather disturbing is that they do not appear to be talking to one another and reading one another's papers.  Or maybe they are simply being ignored.


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Coatless said...

I guess youo know about fraxback now?